Remark

A monogeneric tribe including a single, root-parasitic species, Nuytsia floribunda, considered to represent the first diverging lineage of the Loranthaceae.

Nuytsia floribunda (Labill.) G.Don (Figure 9)

Open in a separate window

Figure 5.

Pollen of Elytrantheae, an Australasian-East Asian Loranthaceae lineage. Pollen images (polar views) are mapped on the corresponding part of the bipartition network shown in Figure 3; Clades A and B according Vidal-Russell and Nickrent (2008b) are indicated. Diagnostic features are highlighted: (a) distinct micro-echinate mesocolpium, becoming micro-verrucate (a′) in Macrosolen and rugulate in Alepis (a″); (b) the partly or fully (Alepis) striate margo, forming triangular polar protrusions (c), weakly developed in Macrosolen (c′); and (d) demisyncolpate apertures found only in Amylotheca.

Open in a separate window

Figure 6.

Pollen of Psittacanthinae, an exclusively New World Loranthaceae lineage. Pollen images (polar views) are mapped on the corresponding part of the bipartition network shown in Figure 3. According to the phylogenetic framework, pollen Types C and D are derived from pollen Type B; the relationship of the only species with pollen Type A is unknown. Several evolutionary trends are indicated: polar outline changes from convex-triangular (a) to straight- to concave-triangular (a′), broadly trilobate (b), and (sub)circular (c); apertures evolve from syncolpate (d) to zonocolpate (d′), parasyncolpate (d″) and demi(syn)colpate (d*); the margo (m) is reduced and becomes indistinct (m′); and the sculpturing of the exine surface smoothens, it can be (micro)baculate or -echinate (e), micro-rugulate (f), or psilate to granulate (g).

Open in a separate window

Figure 7.

Pollen of Lorantheae: Loranthinae, Amyeminae, Scurrulinae, and Dendrophthoinae. Pollen images (polar views) are mapped on the corresponding part of the bipartition network shown in Figure 3; Clades G–J according to Vidal-Russell and Nickrent (2008b) are indicated. Pollen of Loranthus (Loranthinae, Clade G) differs by its zonocolpate aperture organisation (particular on the distal face of heteropolar grains), where the colpi do not join at the pole (a), and the straight-triangular outline in polar view (b′) in contrast to convex-triangular to trilobate (b). Colpi are usually ± narrow, occasionally widening towards the pole joining in a polar depression (c). Note the trend towards T-shaped apices (d) and formation of more or less developed triangular polar protrusions (e) of the more or less prominent margo in the core Lorantheae (Clade J).

Open in a separate window

Figure 8.

Pollen of Lorantheae: Tapinanthinae and Emelianthinae (subclade of Clade J of Vidal-Russell & Nickrent 2008b). Pollen images (polar views) are mapped on the corresponding part of the bipartition network shown in Figure 3. Grains can be isopolar-syncolpate (a), isopolar-zonocolpate (a′) or heteropolar with a syncolpate proximal and zonocolpate distal side (a″); two of the three Tapinanthus species have demisyncolpate pollen (a*). The pollen are either convex-triangular to trilobate in outline (b), sometimes with T-shaped equatorial apices (b′), or more or less straight-triangular (c). Sculpturing in the mesocolpium is nano-verrucate to granulate (d), rarely micro-verrucate (d′), or nano- to micro-baculate/-echinate (e). Abbreviations: d.f., distal face; p.f., proximal face.

Open in a separate window

Figure 9.

LM (A) and SEM (B–I) micrographs of Nuytsia floribunda (WU: origin unknown, coll. Baron F. von Mueller, s.n.). A. Three pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-up of mesocolpium. Scale bars – 10 µm (A), 1 µm (B–I).

Description

Pollen, oblate, trilobate in polar view, elliptic in equatorial view, equatorial apices obcordate; size small, polar axis 10.0–13.3 µm long in LM, equatorial diameter 15.0–18.3 µm in LM, 11.7–13.3 µm in SEM; syn(3)colpate; exine 0.8–1.3 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, micro-echinate to echinate in area of mesocolpium in SEM, echini 0.5–1.4 µm long, 0.4–0.6 µm wide at base; margo well developed, margo mostly psilate around colpi, sometimes partly granulate; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. In overall appearance and size, the pollen of Nuytsia is most similar to that of Gaiadendron, but differs in the sculpturing of the margo (psilate vs. striate in Gaiadendron).

Gaiadendreae

Remark

A tribe with two monotypic (Atkinsonia) or bitypic (Gaiadendron), root-parasitic genera of uncertain phylogenetic affinity (Figures 2, 3) and with markedly different Type B pollen. The pollen of the Australian Atkinsonia is unique (micro-rugulate sculpturing) within the early diverging Loranthaceae. The Central to northern South American Gaiadendron punctatum has a potentially archetypical Type B pollen (Figure 11) relatively similar to pollen of Nuytsia and several Psittacantheae genera of unclear phylogenetic affinity.

Open in a separate window

Figure 10.

LM (A) and SEM (B–I) micrographs of Atkinsonia ligustrina (MEL 2214054). A. Two triangular pollen grains in polar and equatorial view (normal types). One quadrangular pollen grain in polar and equatorial view (rare, abnormal). Two subcircular grains in polar view (aberrant types). B–D. Pollen grains in polar view (normal types). E. Subcircular aberrant pollen grain. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A), 1 µm (B–I).

Open in a separate window

Figure 11.

LM (A) and SEM (B–I) micrographs of Gaiadendron punctatum (WU: from Costa Rica, collector unknown, 5.2.94–912). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A), 1 µm (B–I).

Atkinsonia ligustrina F.Muell (Figure 10)

Description

Pollen, oblate, straight-triangular to convex-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate to rounded; size small, polar axis 8.3–11.7 µm long in LM, equatorial diameter 15.0–18.3 µm in LM, 11.5–16.3 µm in SEM; syn(3)colpate; exine 1.2–1.4 µm thick, nexine thinner than sexine, sexine slightly thickened in area of mesocolpium (LM); tectate, sculpturing psilate in LM, micro-rugulate to micro-areolate in area of mesocolpium in SEM, microareolae often with nano-echinate suprasculpture; margo indistinct, sculptured like mesocolpium; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. Pollen from anthers of Atkinsonia ligustrina are ≥75% syn(3)colpate and straight-triangular to convex-triangular. Aberrant, deformed pollen grains are relatively frequent, ≈20%, and differ in shape/outline (circular to irregular in polar view) and form/arrangement of apertures (irregularly distributed, short/pori like, or absent) and partly SEM sculpturing. Previous studies by Feuer and Kuijt (1980) described and figured only untypical aberrant pollen grains of this species leading them to the wrong conclusion that Atkinsonia is characterised by inaperturate pollen.

Gaiadendron punctatum (Ruiz et Pav.) G.Don (Figure 11)

Description

Pollen, oblate, trilobate in polar view, elliptic in equatorial view, equatorial apices obcordate; size small, polar axis 8.3–15.0 µm long in LM, equatorial diameter 15.8–18.3 µm in LM, 12.0–15.3 µm in SEM; syn(3)colpate; exine 1.1–1.4 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-baculate to nano-echinate in area of mesocolpium in SEM, bacula/echini 0.2–0.5 µm wide at base; margo well developed, margo striate, striae perpendicular to colpi; colpus membrane nano-verrucate to nano-echinate (SEM). – Pollen Type B.

Psittacantheae

Remark

Paraphyletic tribe with one larger and several few-species subtribes including genera of ambiguous phylogenetic affinity (Figures 2, 3; Table III): Ligarinae with Ligaria (monotypic) and Tristerix, Notantherinae with the monotypic genera Desmaria and Notanthera, and the monotypic Tupeinae with Tupeia. Most of the Central and South American members of the Psittacantheae are part of the Psittacanthinae that fall within a distinct and well-supported clade in molecular trees, and are described in the next section. The only Psittacanthinae genus placed outside the Psittacanthinae clade in our reconstructions (Figures 2, 3) is Aetanthus. Note that this is a misplacement due to insufficient data (only 18S rDNA data included here, see File S2). The correct placement is as sister to Psittacanthus (anonymous reviewer, personal communication, 2016), as informed by matK data (Vidal-Russell & Nickrent 2008b; Su et al. 2015).

Ligarinae

Ligaria cuneifolia (Ruiz et Pav.) Tiegh. (Figure 12)

Open in a separate window

Figure 12.

LM (A) and SEM (B–I) micrographs of Ligaria cuneifolia (WU: from Argentina, collector unknown, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, (concave-)triangular in polar view, emarginate in equatorial view, equatorial apices rounded to obcordate; size medium, polar axis 11.7–13.3 µm long in LM, equatorial diameter 25.0–30.0 µm in LM, 24.1–29.0 µm in SEM; syn(3)colpate; exine 1.1–1.3 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, micro-baculate in area of mesocolpium in SEM, microbacula 0.5–1.1 µm long, 0.2–0.5 µm wide at base; margo indistinct, margo sculptured like mesocolpium; colpus membrane nano-verrucate to nano-echinate and granulate (SEM).

Remark

Pollen Type B. Pollen of Ligaria is very distinct, being characterised by a very indistinct margo sculptured in the same way as the mesocolpium. Differing markedly in outline, it shares the feature of a markedly reduced polar sexine with its putative sister genus Tristerix.

Tristerix aphyllus (Miers ex DC.) Barlow et Wiens (Figure 13)

Open in a separate window

Figure 13.

LM (A) and SEM (B–I) micrographs of Tristerix aphyllus (WU 066237). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, trilobate (gear wheel-like) in polar view, emarginate in equatorial view, equatorial apices obcordate; size small, polar axis 6.6–8.3 µm long in LM, equatorial diameter 20.0–21.7 µm in LM, 18.6–20.5 µm in SEM; syn(3)colpate; exine 1.1–1.5 µm thick, nexine thinner than sexine, triangular intercolpial nexine thickenings in polar area (LM), sexine partly reduced in polar area, colpi widening to a small field (SEM); tectate; sculpturing psilate in LM, nano-/micro-echinate to nano-/micro-baculate in area of mesocolpium in SEM, echini/bacula 0.3–0.8 µm long, 0.2–0.4 µm wide at base; margo well developed, margo striate, striae perpendicular to colpi, margo with triangular protrusions in polar area (SEM).

Remark

Pollen Type B. The outline of Tristerix pollen in polar view is unique within the family, reflecting the genetic distinctness of the genus (Figure 2; Su et al. 2015). The pollen has a nearly rounded central body and narrow, straight equatorial apices (lobes), giving it the appearance of a gear wheel with three teeth. Similar equatorial apices can be found occasionally in species of other genera (Psittacanthus rhynchanthus, Psittacanthinae; Actinanthella menyhartii, Tapinanthinae), but these pollen differ in the shape of the central body (essentially triangular with retracting mesocolpium towards equatorial apices) and the sculpturing of the margo and mesocolpium.

Tristerix longebracteatus (Desr.) Barlow et Wiens (Figure 14)

Open in a separate window

Figure 14.

LM (A) and SEM (B–I) micrographs of Tristerix longibracteatus (WU: from Ecuador, coll. J. Jaramillo, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H. Close-up of mesocolpium. I. Close-up of margo in central polar area. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, trilobate in polar view, emarginate in equatorial view, equatorial apices obcordate; size medium, polar axis 13.3–15.0 µm long in LM, equatorial diameter 36.6–41.7 µm in LM, 32.7–38.2 µm in SEM; syn(3)colpate; exine 1.3–1.7 µm thick, nexine thinner than sexine, triangular intercolpial nexine thickenings in polar area (LM), sexine partly reduced in polar area, colpi widening to a small field (SEM); tectate; sculpturing psilate in LM, nano-/micro-echinate to nano-/micro-baculate in area of mesocolpium in SEM, echini/bacula 0.3–0.7 µm long, 0.2–0.5 µm wide at base; margo well developed, margo striate, striae perpendicular to colpi, margo with triangular protrusions in polar area; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. Pollen of Tristerix longebracteatus are very similar to those of T. aphyllus, they differ manly in size. Tristerix longebracteatus pollen grains are much larger. In addition, the striae on the margo are less distinct (compare Figure 13G with Figure 14G).

Notantherinae

Desmaria mutabilis (Poepp. et Endl.) Tiegh. ex B.D.Jacks.

Description (cf. Feuer & Kuijt 1980, figures 29, 31, 32, 34)

Pollen, distinctly oblate, trilobate in polar view, elliptic in equatorial view, equatorial apices obcordate; size medium (cf. Feuer & Kuijt 1980, table 1); syn(3)colpate; polar ectexine and entexine thickened (TEM); tectate; not figured in LM, sculpturing probably micro-baculate to micro-echinate in SEM; margo well developed, forming triangular polar protrusions, striate, with striae perpendicular to colpi (SEM).

Remark

Pollen Type B. The pollen of Desmaria is substantially different from that of its morphologically closest relative Notanthera, the other genus of the Notantherinae (but see Su et al. 2015). It is similar to the pollen found in the Elytrantheae, but shares the striate margo seen in several of the early diverging Loranthaceae listed in Table III. Its phylogenetic position is essentially unresolved based on molecular data (Figures 2, 3; Su et al. 2015).

Notanthera heterophylla (Ruiz et Pav.) G.Don

Description (cf. Feuer & Kuijt 1980, figures 5, 22)

Pollen, oblate, concave-triangular in polar view, not figured in equatorial view, equatorial apices obcordate; size small (cf. Feuer & Kuijt 1980, table 1); syn(3)colpate; tectate; not figured in LM, sculpturing probably nano-baculate/-echinate in SEM; margo well developed, forming triangular polar protrusions, psilate at pole, weakly striate in mesocolpium (SEM).

Remark

Pollen Type B. Within the group of Loranthaceae with unclear affinity the character suite showed by pollen of Notanthera is unique. It combines features such as a (partly) striate margo as seen in Desmaria (same subtribe), Gaiadendron, and Tristerix, a prominent margo as seen in large-flowered Psittacanthinae (the sister group according to Vidal-Russell & Nickrent [2008b, figure 3], and Su et al. [2015, figure 2]) with a sculpturing in the mesocolpium that shows an overall resemblance to pollen of the Lorantheae.

Tupeinae

Tupeia antarctica (G. Forst.) Cham. et Schltdl. (Figure 15)

Open in a separate window

Figure 15.

LM (A) and SEM (B–I) micrographs of Tupeia antarctica (MO: from New Zealand, coll. R. Gardner, s.n.). A. Five pollen grains in equatorial and polar view, two zono(3)colpate grains followed by three zono(4)colpate grains. B. Zono(3)colpate grain in polar view. C. Zono(4)colpate grain in polar view. D, E. Pollen grains in equatorial view. F. Close-up of central polar area. G. Close-up of colpi. H. Close-up of mesocolpium. I. Close-up of colpi and colpus membrane. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 16.

LM (A) and SEM (B–I) micrographs of Amylotheca sp. (WU: from Philippines, coll. Sterner, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 17.

LM (A) and SEM (B–I) micrographs of Alepis flavida (WU: from New Zealand, coll. Raven, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, spheroidal to slightly oblate, subcircular in polar and equatorial view; size small to medium, polar axis 18.3–21.7 µm long in LM, 20.0–22.0 in SEM, equatorial diameter 23.0–25.0 µm in LM, 21.4–24.4 µm wide in SEM; zono(3–4)colpate, colpi short and wide, colpi 8.0–9.5 µm long in SEM; exine 1.2–1.7 µm thick, nexine thinner than sexine (LM); tectate; sculpturing uniform, echinate in LM and SEM, echini 0.8–1.6 µm long, 0.5–1.2 µm wide at base; colpus membrane micro-echinate to echinate (SEM).

Remark

Pollen Type A. The spheroidal, echinate pollen of Tupeia is most distinct within Loranthaceae. The only species with a similar pollen morphology and structural elements of similar size is Phthirusa hutchisonii, an isolated Psittacanthinae species of unknown phylogenetic relationships (see ‘Discussion’).

Elytrantheae clade

All five genera of the Elytrantheae studied here using LM and SEM (Figure 5: Amylotheca [Figure 16], Alepis [Figure 17], Loxanthera [Figure 18], Macrosolen [Figure 19], Peraxilla [Figures 20, 21]) share similar pollen of Type B. Pollen grains are syn(3)colpate except for Amylotheca, (distinctly) oblate and more or less deeply concave-triangular in polar outline; the equatorial apices are truncated to broadly rounded. The margo is well-developed, encompassing the equatorial apices, and producing three more or less pronounced triangular intercolpial protrusions at the poles, a shared feature of the lineage. Linked to this is that the colpi are typically widening towards the polar area. Another diagnostic SEM feature is that the sculpturing of the margo gradually changes from psilate (the basic sculpturing in all putatively derived Loranthaceae) at the equator to more or less distinctly striate (as in several Loranthaceae of ambiguous affinity; Figure 4; Table III) in the polar area. Amylotheca, a genus deeply nested in the clade as sister to Loxanthera, differs from the basic type by several characteristics, all of which appear to be directly derived from the basic type seen in the other genera (Figure 5). The pollen of the eight Elytrantheae species including one sp. indet. (two Amylotheca, one Elytranthe, five Macrosolen) figured in Liu and Qiu (1993) and Han et al. (2004) seem to fall within the here documented general type.

Open in a separate window

Figure 18.

LM (A) and SEM (B–I) micrographs of Loxanthera speciosa (WU: from Sumatra, coll. H. O. Forbes, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E, G), 1 µm (F, H, I).

Open in a separate window

Figure 19.

LM (A) and SEM (B–I) micrographs of Macrosolen cochinchinensis (WU 039103). A. Two pollen grains, upper in equatorial view and lower in polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 20.

LM (A) and SEM (B–I) micrographs of Peraxilla colensoi (WU: from New Zealand, coll. G. Schneeweiß, P. Schönswetter and A. Tribsch, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 21.

LM (A) and SEM (B–I) micrographs of Peraxilla tetrapetala (WU: from New Zealand, coll. G. Schneeweiß, P. Schönswetter and A. Tribsch, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Elytrantheae

Amylotheca sp.

(Figure 16)

Description

Pollen, oblate, concave-triangular in polar view, rhombic (acuminate-obtuse) in equatorial view, equatorial apices rounded; size small, polar axis 10.0–15.0 µm long in LM, equatorial diameter 18.3–21.7 µm in LM, 19.5–20.9 µm in SEM; demisyn(3)colpate, colpi short, 6.7–8.5 µm long in SEM, colpi widening towards polar area; exine 1.0–1.3 µm thick, nexine thinner than sexine, nexine thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-echinate in area of mesocolpium in SEM, echini 0.2–0.6 µm long, 0.2–0.4 µm wide at base; margo well developed, margo psilate, margo with triangular protrusions in polar area; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. The unique characteristics of Amylotheca pollen within the Elytrantheae include its small size, its rhombic outline in equatorial view, its psilate margo, and that it is demisyncolpate.

Alepis flavida Tiegh. (Figure 17)

Description

Pollen, distinctly oblate, concave-triangular to trilobate in polar view, elliptic in equatorial view, equatorial apices broadly rounded; size medium, polar axis 18.3–20.0 µm long in LM, equatorial diameter 36.7–43.3 µm in LM, 35.8–41.8 µm in SEM; syn(3)colpate, colpi widening towards polar area; exine 1.3–1.7 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, rugulate in area of mesocolpium in SEM; margo well developed, margo striate, striae mostly perpendicular to colpi, margo sometimes psilate at equatorial apices, margo with triangular protrusions in polar area; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. Pollen of Alepis and its sister genus Peraxilla are very similar in general morphology (outline, size, thickenings, etc.). A unique feature of Alepis pollen is the rugulate sculpturing in the mesocolpium, and linked to this, a distinctly striate margo. The margo is weakly but visibly striate in Peraxilla, which has a nano-echinate sculpturing in the area of mesocolpium.

Elytranthe albida (Blume) Blume

Description (cf. Liu & Qiu 1993, plate I, figures 12–15; Han et al. 2004, figures 13–15)

Pollen, distinctly(?) oblate, concave-triangular in polar view, equatorial view unknown, equatorial apices truncated(?); size medium (to large?; cf. tables in Liu & Qiu 1993; Han et al. 2004); syn(3)colpate; further details not visible.

Remark

Pollen Type B. As far as can be judged from the original micrographs, pollen of this species falls within the typical morphology of the Elytrantheae.

Loxanthera speciosa Blume (Figure 18)

Description

Pollen, oblate, concave-triangular to straight-triangular in polar view, elliptic in equatorial view, equatorial apices broadly rounded; size medium to large, polar axis 30.0–32.0 µm long in LM, equatorial diameter 46.7–58.3 µm in LM, 40.0–51.1 µm in SEM; syn(3)colpate, colpi widening towards polar area; exine 1.3–1.7 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, micro-echinate to echinate in area of mesocolpium in SEM, echini broadly based, echini 0.3–1.2 µm long, 0.5–1.7 µm wide at base; margo well developed, margo striate to rugulate in polar area, margo psilate at equatorial apices, striae/rugulae perpendicular to colpi, margo with triangular protrusions in polar area; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. The pollen stands out within this group because of its size and the size of its sculpturing elements.

Macrosolen cochinchinensis (Lour.) Tiegh. (Figure 19)

Description

Pollen, oblate, concave-triangular in polar view, elliptic in equatorial view, equatorial apices broadly rounded; size medium, polar axis 18.0–20.0 µm long in LM, equatorial diameter 30.0–35.0 µm in LM, 23.5–32.8 µm in SEM; syn(3)colpate, colpi widening towards polar area; exine 1.2–1.7 µm thick, nexine thinner than sexine (LM); tectate; sculpturing psilate in LM, micro-verrucate to micro-echinate, perforate in area of mesocolpium in SEM; margo well developed, margo psilate and/or indistinctly striate/rugulate, striae/rugulae perpendicular to colpi; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. This pollen differs from other pollen of the group by its variable mesocolpial sculpturing (micro-verrucate to -echinate, perforate).

Peraxilla colensoi (Hook.f.) Tiegh.

(Figure 20)

Description

Pollen, distinctly oblate, concave-triangular in polar view, elliptic in equatorial view, equatorial apices broadly rounded; size medium, polar axis 10.0–16.7 µm long in LM, equatorial diameter 28.3–31.7 µm in LM, 27.6–31.4 µm in SEM; syn(3)colpate, colpi widening towards polar area; exine 1.4–1.8 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area, sexine thickened in area of mesocolpium (LM); tectate; sculpturing psilate in LM, nano-echinate in area of mesocolpium in SEM, echini 0.3–0.6 µm long, 0.2–0.5 µm wide at base; margo well developed, margo psilate and/or slightly striate/rugulate, striae/rugulae perpendicular to colpi, margo with prominent triangular protrusions in polar area; colpus membrane nano-verrucate to nano-echinate (SEM). – Pollen Type B.

Peraxilla tetrapetala (L.f.) Tiegh. (Figure 21)

Description

Pollen, distinctly oblate, concave-triangular in polar view, elliptic in equatorial view, equatorial apices broadly rounded; size medium, polar axis 8.3–11.7 µm long in LM, equatorial diameter 30.0–35.0 µm in LM, 27.1–32.1 µm in SEM; syn(3)colpate, colpi widening towards polar area; exine 1.1–1.5 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-echinate in area of mesocolpium in SEM, echini 0.3–0.6 µm long, 0.2–0.4 µm wide at base; margo well developed, margo psilate and/or striate/rugulate, striae/rugulae perpendicular to colpi, margo with prominent triangular protrusions in polar area; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. The pollen of both investigated species of Peraxilla are nearly identical.

Psittacanthinae clade

The Psittacanthinae show substantial variation in their pollen morphology, covering all four main pollen types, three of which (Type B, C, and D) can be linked with the molecular-phylogenetic framework (Figure 6). The Type D pollen characteristic for Oryctanthus is highly distinct in LM and SEM (Figure 25); the same holds for the pollen Type A of Phthirusa hutchisonii and pollen Type C of Dendropemon and its close relative Passovia pyrifolia (Figure 28; Feuer & Kuijt 1985). Also the pollen Type B found in other species of Passovia and Phthirusa and the remaining genera (Figures 22–24, 26, 27, 29–34) is divers. It includes small to large-sized (rare), oblate to extremely oblate (more than three-times wider than high in equatorial view) pollen grains that vary from (deeply) concave- to convex-triangular outline in polar view. Pollen grains are mostly elliptic in equatorial outline, but can also be (sub-)rhombic (Struthanthus uraguensis G.Don, Tripodanthus belmirensis F.J.Roldán et Kuijt) or emarginate (several Psittacanthus species; Tables V, VI). Aperture organisation is variable between, but also within genera; basically syncolpate, apertures are further modified into zono-, demi-, parasyn- or potentially demisyncolpate (Figure 6). For a few species of Struthanthus, heteropolar grains have been documented (S. dichotrianthus Eichler) or purported (S. deppeanus [Schltdl. et Cham.] G.Don, S. marginatus [Desr.] Blume; Feuer & Kuijt 1985). Colpi are narrow to wide, and occasionally widening towards the equatorial apices (Psittacanthus calyculatus) or polar area (Cladocolea, a few Struthanthus spp., less developed in Peristethium). The colpi form seems not to be phylogenetically correlated. Traits like a distinct, essentially psilate margo seem however to be restricted to certain genera and subclades of the Psittacanthinae (Figure 6; Tables V–VII). LM images of Cladocolea and species of its sister genus Struthanthus indicate a narrow-elliptical to U-shaped thinning perpendicular to the colpi in the nexine between the pole and the equator (see ‘Discussion’); in other Struthanthus and Tripodanthus species the sexine appears to be thickened in the equatorial mesocolpium (Tables V, VI). Polar thickening of inner (observed under LM) and outer exine layers (observed under SEM) is found in species of all genera with pollen Type B. Outer exine thickening manifests either as a polar dome overgrowing the colpi (in a Passovia species with pollen Type B synonymised with Passovia pyrifolia, which has pollen Type C) or as a more or less pronounced, protruding island in the apocolpial field in grains with parasyncolpate aperture organisation, a feature typical for the Cladocolea-Struthanthus lineage (minute in Peristethium leptostachyum). The mesocolpium sculpturing is often unclear in previously published images, but anything can be found from psilate or granulate to micro-baculate, -echinate and -verrucate. A unique ornamental feature within the Loranthaceae is the minute rugulate sculpturing found in the mesocolpium of pollen of several Struthanthus species (Struthanthus ‘Type 3’ in Feuer & Kuijt 1985), which can be rugulate to striate in Peristethium leptostachyum, which has been recently moved from Struthanthus (Figure 29; Table VI). Sculptural elements (bacula) >1 µm are restricted to pollen of the genus Tripodanthus (Figure 34), resolved as sister to all other Psittacanthinae except the extremely long-branching Phthirusa (Figures 2, 6).

Open in a separate window

Figure 22.

LM (A) and SEM (B–I) micrographs of Aetanthus coriaeus (MO: from Ecuador, coll. J. E. Madsen, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 23.

LM (A) and SEM (B–I) micrographs of Aetanthus macranthus (MO: from Ecuador, coll. unknown, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 24.

LM (A) and SEM (B–I) micrographs of Aetanthus nodosus (MO: from Ecuador, coll. S. González, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 25.

LM (A) and SEM (B–I) micrographs of Oryctanthus alveolatus (WU: from Ecuador, coll. J. R. Abbott, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F, G, H. Close-ups of lophae junction showing colpus (arrow) and adjacent mesocolpium (mc) and apocolpium (ac). I. Close-up of polar lacuna. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 26.

LM (A) and SEM (B–I) micrographs of Passovia ovata (MO: from Brazil, coll. J. Ratter, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 27.

LM (A) and SEM (B–I) micrographs of Passovia pedunculata (MO: from Venezuela, coll. Liesner, s.n.). A. Two pollen grains in equatorial and polar view. B–D. Pollen grains in polar view. E. Pollen grain in equatorial view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 28.

LM (A) and SEM (B–I) micrographs of Passovia pyrifolia (MO: from Peru, coll. R. Várgez & N. Jaramillo, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 29.

LM (A) and SEM (B–I) micrographs of Peristethium leptostachyum (WU 026391). A. Four pollen grains in equatorial and polar view. B–D. Pollen grains in polar view. E. Pollen grain in equatorial view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A), 1 µm (B–I).

Open in a separate window

Figure 30.

LM (A) and SEM (B–I) micrographs of Phthirusa clandestina (MO: from Brazil, coll. Harley et al., s.n.). A. Three pollen grains in equatorial and polar view. B–D. Pollen grains in polar view. E. Pollen grain in equatorial view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A, B), 1 µm (C–I).

Open in a separate window

Figure 31.

LM (A) and SEM (B–I) micrographs of Phthirusa hutchisonii (from Colombia, coll. Hutchinson & Idrobo, MO s.n.). A. Four pollen grains in equatorial and polar view. B–D. Pollen grains in equatorial view. E. Pollen grain in polar view. F. Close-up of central polar area. G. Close-up of colpi. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 32.

LM (A) and SEM (B–I) micrographs of Psittacanthus calyculatus (WU: from Mexico, coll. C. G. Pringle, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 33.

LM (A) and SEM (B–I) micrographs of Psittacanthus rhynchanthus (WU 020859). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H. Close-up of mesocolpium. I. Close-up of central polar area. Scale bars – 10 µm (A–E), 1 µm (F–I).

Open in a separate window

Figure 34.

LM (A) and SEM (B–I) micrographs of Tripodanthus acutifolius (WU: from Bolivia, coll. N. A. Harriman, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area and mesocolpium. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A, B, D), 1 µm (C, E–I).

Aetanthus coriaceus Patsch. (Figure 22)

Description

Pollen, oblate, trilobate to concave-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate to rounded; size medium, polar axis 20.0–23.3 µm long in LM, equatorial diameter 36.6–45.0 µm in LM, 31.9–43.5 µm in SEM; syn(3)colpate; exine 1.3–1.6 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-baculate to micro-baculate in area of mesocolpium in SEM, bacula 0.3–0.9 µm long, 0.2–0.4 µm wide at base; margo well developed, margo mostly psilate, partly nano-/micro-baculate (SEM). – Pollen Type B.

Aetanthus macranthus (Hook.) Kuijt (Figure 23)

Description

Pollen, oblate, trilobate to concave-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size medium, polar axis 23.3–26.7 µm long in LM, equatorial diameter 45.0–48.3 µm in LM, 39.0–45.0 µm in SEM; syn(3)colpate; exine 1.2–1.7 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-baculate to micro-baculate in area of mesocolpium in SEM, bacula 0.3–0.8 µm long, 0.2–0.4 µm wide at base; margo well developed, margo mostly psilate, partly nano-/micro-baculate (SEM). – Pollen Type B.

Aetanthus nodosus (Desr.) Engl. (Figure 24)

Description

Pollen, oblate, trilobate to straight-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate to rounded; size medium, polar axis 18.3–25.0 µm long in LM, equatorial diameter 38.3–45.0 µm in LM, 31.5–40.0 µm in SEM; syn(3)colpate; exine 1.3–1.7 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-baculate to micro-baculate in area of mesocolpium in SEM, bacula 0.3–0.8 µm long, 0.2–0.5 µm wide at base; margo well developed, margo mostly psilate, partly nano-/micro-baculate (SEM).

Remark

Pollen Type B. The pollen of all three investigated Aetanthus species are very similar. In a larger taxonomic context, the pollen better fits with the systematic placement as member of the Psittacanthinae than as sister to Desmaria (Notantherinae, Figures 2, 3), a placement based exclusively on its 18S rDNA data. Within the Psittacantheae clade, the pollen of Aetanthus supports a closer relationship to Psittacanthus and Tripodanthus, which is in line with molecular trees relying on matK data (File S1; Vidal-Russell & Nickrent 2008b, figure 2; Su et al. 2015).

Cladocolea spp. (Table VI)

General description based on the species figured in Feuer and Kuijt (1985; see Files S3, S4)

Pollen, oblate, straight- to convex-triangular in polar view, elliptic in equatorial view, equatorial apices rounded or obcordate; size medium (cf. Feuer & Kuijt 1985, table 1); (demi)parasyn(3)colpate, potentially demisyn(3)colpate in Cladocolea micrantha (Eichler) Kuijt; parasyncolpate grains typically with nexine thinning perpendicular to colpi and triangular polar thickening; tectate; sculpturing psilate in LM, not clear in SEM; parasyncolpate pollen with a protruding apocolpial field (SEM).

Remark

Pollen Type B. From its overall appearance and lacking all unique features of other species of the genus, the pollen of Cladocolea micrantha (a species formerly included in Phthirusa) would better fit within the variation seen in other genera of Psittacanthinae (Struthanthus, Passovia).

Dendropemon spp. (Table VII)

General description based on the species figured in Feuer and Kuijt (1985; see Files S3, S4)

Pollen, oblate, broadly trilobate in polar view, subrhombic (?) in equatorial view, equatorial apices broadly rounded; size medium (cf. Feuer & Kuijt 1985, table 1); demi(3)colpate with short and wide colpi; triradial nexine thickening in polar ares (LM; also seen in TEM); tectate; sculpturing psilate in LM, not clear in SEM.

Remark

Pollen Type C. The pollen of Dendropemon is readily distinct from most other Loranthaceae due to its unique apertures and shape. Only pollen of Passovia pyrifolia is somewhat similar (Figure 28; Feuer & Kuijt 1985).

Maracanthus chlamydatus (Rizzini) Kuijt

(Table VII)

Description (cf. Feuer & Kuijt 1985, figures 4, 50, 53, 67)

Pollen, oblate, straight-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size medium (cf. Feuer & Kuijt 1985, table 1); syn(3)colpate with short and wide colpi; nexine thickened in polar ares (LM); tectate; sculpturing psilate in LM, not clear in SEM, but minute, perforate (TEM).

Remark

Pollen Type B. Nickrent et al. (2010) included this genus in Oryctina.

Oryctanthus alveolatus (Kunth) Kuijt (Figure 25; Table VII)

Description

Pollen, oblate, (sub-)circular in polar view, elliptic in equatorial view; size medium, polar axis 16.7–21.7 µm long in LM, equatorial diameter 33.3–41.6 µm in LM, 32.2–35.7 µm in SEM; demi(3)colpate, colpi very narrow; exine 1.1–1.6 µm thick, nexine thinner than sexine (LM); pollen lophate, apocolpium with triradial symmetry, apocolpial lophae surrounding three large (intercolpial) lacunae, radial lophae straight and joining at the pole, mesocolpial lophae irregularly spaced and decreasing in height towards the ridged equator (LM, SEM); tectate; sculpturing psilate in LM, mostly psilate with granulate patches in SEM.

Remark

Pollen Type D. The unique pollen of Oryctanthus cannot be confused with any other angiosperm, neither in LM nor SEM. Caires (2012) figured pollen from 11 species of the genus.

Oryctina spp. (Table VII)

General description based on the two species figured in Feuer and Kuijt (1985, LM) and Caires (2012, SEM)

Pollen, shape unknown, straight- or convex-triangular in polar view (no equatorial view available), equatorial apices broadly rounded or obcordate; size small; demi(?)syn(3)colpate, colpi narrow; triradial thickening of nexine in polar area (LM); tectate; sculpturing psilate in LM, unclear (uniform?) in SEM.

Remark

Pollen Type B. At the moment little can be said about the morphological affinity of Oryctina pollen because of the lack of published material. From the available micrographs Oryctina pollen is more similar to that of Struthanthus or pollen Type B of Passovia than those of the other genera.

Panamanthus panamensis (Rizzini) Kuijt (Table VII)

Description (cf. Feuer & Kuijt 1985, figures 19, 79, 90–92)

Pollen, oblate, concave-triangular to broadly lobate in polar view (no equatorial view available), equatorial apices broadly rounded; size medium; demi(3)colpate, colpi short and narrow, nexine thickened in polar area (LM); tectate; sculpturing psilate in LM, unclear in SEM.

Remark

Possibly pollen Type C. Except for its narrow colpi, the grain resembles the grains of Passovia pyrifolia and Dendropemon (to a lesser degree), and may represent an intermediate form between Type B and Type C or a less derived variant of Type C. Further palynological and genetic investigations are warranted, but the pollen can be used as argument against including this monotypic genus in Struthanthus.

Passovia ovata (DC.) Kuijt (Figure 26; Table VII)

Description

Pollen, oblate, concave-triangular in polar view, broadly elliptic in equatorial view, equatorial apices broadly rounded; size medium, polar axis 20.0–23.3 µm long in LM, equatorial diameter 33.3–36.7 µm in LM, 29.6–33.6 µm in SEM; demisyn(3)colpate to demi(3)colpate, colpi long and wide; exine 1.3–1.7 µm thick, nexine thinner than sexine (LM); tectate; sculpturing psilate in LM, micro-rugulate to rugulate, fossulate, and perforate in area of mesocolpium in SEM; margo well developed, margo psilate; colpus membrane nano-verrucate to nano-echinate (SEM). – Pollen Type B.

Passovia pedunculata (Jacq.) Kuijt (Figure 27; Table VII)

Description

Pollen, oblate, straight-triangular to convex-triangular in polar view, broadly elliptic in equatorial view, equatorial apices broadly rounded; size medium, polar axis 25.0–28.3 µm long in LM, equatorial diameter 35.0–40.0 µm in LM, 31.3–35.4 µm in SEM; demisyn(3)colpate to demi(3)colpate, colpi long and wide; exine 1.2–1.6 µm thick, nexine thinner than sexine, nexine thickened in polar area (LM); tectate; sculpturing psilate in LM, micro-rugulate to rugulate, fossulate, and perforate in area of mesocolpium in SEM; margo well developed, margo psilate; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. The pollen is highly similar to that of Passovia ovata (Figure 26), possibly also P. coarctata (A.C.Smith) Kuijt and P. lepidobotrys (Griseb.) Kuijt (cf. Feuer & Kuijt 1985, figures 1, 51, 52), but markedly different from P. pyrifolia (Figure 28).

Passovia pyrifolia (Kunth.) Tiegh. (Figure 28; Table VII)

Description

Pollen, oblate, broadly trilobate in polar view, elliptic to subrhombic in equatorial view, equatorial apices broadly rounded; sizes mall to medium, polar axis 15.0–20.0 µm long in LM, equatorial diameter 25.0–28.3 µm in LM, 20.4–23.7 µm in SEM; demi(3)colpate, colpi short and wide, colpi 2.2–5.1 µm long in SEM; exine 1.1–1.5 µm thick, nexine thinner than sexine, triradial thickening of nexine in polar area (LM); tectate; sculpturing psilate in LM, micro-rugulate to rugulate, fossulate, and perforate in area of mesocolpium in SEM; margo well developed, margo psilate; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type C. The pollen of Passovia pyrifolia (including Phthirusa platyclada, but not Passovia lepidobotrys; cf. Kuijt 2011; Tropicos.org 2016) is unlike the pollen Type B in all other Passovia species studied so far. It differs from that of Panamanthus (potential Type C) by its widened colpi, pronounced triradial thickening in the polar area visible both in LM and SEM, and general higher similarity to the pollen Type C of Dendropemon.

Peristethium leptostachyum (Kunth.) Tiegh. (Figure 29; Table VI)

Description

Pollen, oblate, convex-triangular to straight-triangular in polar view, elliptic in equatorial view, equatorial apices broadly rounded; size small, polar axis 8.3–10.0 µm long in LM, equatorial diameter 15.0–17.5 µm in LM, 14.3–17.3 µm in SEM; syn(3)colpate to demisyn(3)colpate, colpi long; exine 0.8–1.1 µm thick, nexine thinner than sexine, triangular intercolpial nexine thickenings in polar area (LM), some grains with a minute protruding island in central polar area (SEM); tectate; sculpturing psilate in LM, rugulate to striate in mesocolpium and polar area in SEM; margo absent, colpus membrane nano-rugulate (SEM).

Remark

Pollen Type B. Feuer and Kuijt (1979) classified the pollen of Struthanthus leptostachyus (Kunth) G.Don, which recently was included in Peristethium, as ‘Type Ia1/b1’ in their study of the genus (cf. File S4). Features shared by some Struthanthus species and Peristethium leptostachyum are (partly) demicolpate apertures (also found in S. hartwegii [Benth.] Standl.), a rugulate sculpturing (shared with several other species), and a polar area with a protruding central part (several species). Compared with available micrographs of Struthanthus species, the here figured pollen of P. leptostachyum shows a unique character suite. Most notably, it is so far the only pollen from the Cladocolea-Struthanthus lineage with a partly striate sculpturing. Caires et al. (2014) moved another species from Struthanthus to Peristethium, and also figure the pollen in SEM (polar view). The pollen has a similar general appearance, but details of the sculpturing are not visible in the micrograph. There is no molecular data on the genus.

Phthirusa clandestina (Mart. ex Roem. et Schult.f.) Mart. (Figure 30; Table VII)

Description

Pollen, oblate, straight-triangular in polar view, broadly elliptic in equatorial view, equatorial apices broadly rounded to obcordate; size small, polar axis 15.0–16.7 µm long in LM, equatorial diameter 18.3–23.3 µm in LM, 15.3–22.2 µm in SEM; syn(3)colpate; exine 0.9–1.4 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area, sexine thickened in area of mesocolpium (LM); tectate; sculpturing psilate in LM, micro-rugulate in area of mesocolpium in SEM; margo fairly well developed, margo micro-rugulate to psilate and perforate; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. The pollen shows a unique character suite and is most similar to that of Passovia ovata and P. pedunculata. It differs from these by being syncolpate with a margo that is sculptured in the same way as the mesocolpium (micro-rugulate in contrast to psilate in species of Passovia).

Phthirusa hutchisonii (Kuijt) Kuijt (Figure 31; Table VII)

Description

Pollen, spheroidal to slightly oblate, outline circular to lobate in polar view, circular to elliptic in equatorial view; size small to medium, polar axis 23.3–26.7 µm long in LM, 22.8–28.6 µm in SEM, equatorial diameter 26.7–31.7 µm in LM, 22.3–32.0 µm in SEM; zono(4)colpate, colpi short; exine 1.0–1.5 µm thick, nexine thinner than sexine (LM); tectate; sculpturing uniform, echinate in LM and SEM, echini 0.9–2.5 µm long, 0.5–1.2 µm wide at base; colpus membrane nano-echinate (SEM).

Remark

Pollen Type A. The only Loranthaceae with an equally atypical pollen is Tupeia antarctica from New Zealand (see earlier). Feuer and Kuijt (1985) note additional 3- and 5-colpate grains, not observed in our material.

Psittacanthus calyculatus (DC.) G.Don (Figure 32; Table V)

Description

Pollen, distinctly oblate, straight-triangular to concave-triangular in polar view, emarginate in equatorial view, equatorial apices truncated; size small to medium, polar axis 6.7–10.0 µm long in LM, equatorial diameter 23.3–31.7 µm in LM, 22.5–26.7 µm in SEM; syn(3)colpate; exine 1.0–1.3 µm thick, nexine thinner than sexine (LM); tectate; sculpturing psilate in LM, nano-echinate to micro-echinate in area of mesocolpium in SEM, echini 0.3–0.9 µm long, 0.2–0.6 µm wide at base; margo well developed, widening in equatorial region, margo psilate (SEM).

Remark

Pollen Type B. Feuer and Kuijt (1979) studied the pollen of 30 Psittacanthus species (including 12 that are now treated as synonyms) and established several types and subtypes, figuring exemplary specimens including P. calyculatus (representing ‘Type Ib’). Species with similar syncolpate pollen and nano- to micro-echinate sculpturing are P. columbianus A.C.Sm., P. macranthus Hook (species does not exist, Tropicos.org 2016; R. Vidal-Russell, personal communication, 2016), P. schiedeanus (Schtdl. et Cham.) G.Don, P. sonorae (S.Watson) Kuijt. (‘Type Ia’), and P. clusiifolius Eichler (‘Type Id’; Files S3, S4; Table V).

Note

Pollen surface features seen in the LM micrographs are not reflecting sculptural elements but cell contain contents and flower material, due to incomplete acetolisation. Fully processed grains had the tendency to rupture and lose their form, so we opted to interrupt the acetolising process for LM photography.

Psittacanthus rhynchanthus (Benth.) Kuijt (Figure 33; Table V)

Description

Pollen, distinctly oblate, concave-triangular to trilobate in polar view, emarginate in equatorial view, equatorial apices obcordate; size medium, polar axis 10.0–13.0 µm long in LM, equatorial diameter 25.0–33.3 µm in LM, 25.3–28.2 µm in SEM; zono(3)colpate, colpi of medium length; exine 1.1–1.5 µm thick, nexine thinner than sexine (LM); tectate; sculpturing psilate in LM, nano-/micro-baculate to nano-/micro-echinate in area of mesocolpium and polar area in SEM, bacula/echini 0.3–1.0 µm long, 0.2–0.4 µm wide at base; margo well developed, margo psilate (SEM).

Remark

Pollen Type B. Zonocolpate grains are rarer in species of Psittacanthus. Further species with zonocolpate grains are P. cucullaris (Lam.) G.Don and P. dilatatus A.C.Sm. (Table V; Feuer & Kuijt 1979; Files S3, S4) Pollen of these two species are generally similar to the pollen of P. rhynchanthus. However, Feuer and Kuijt (1979) included these three species in types (‘Type Ib’, ‘Type Ic’) with syncolpate pollen (see ‘Discussion’).

Struthanthus spp.

General description based on the species figured in Feuer and Kuijt (1985; see Files S4, S5)

Pollen, (distinctly) oblate, straight- to convex-triangular in polar view, elliptic, slightly emarginate or subrhombic in equatorial view, equatorial apices truncated, rounded or obcordate; size medium (cf. Feuer & Kuijt 1985, table 1); demi- or parasyn(3)colpate or syn(3)colpate, some with nexine thinning perpendicular to colpi and, others with triangular polar thickening; tectate; sculpturing psilate in LM, not clear in SEM for most species, some (S. concinnus Mart., S. marginatus, S. uraguensis) rugulate; parasyncolpate pollen with a protruding apocolpial field (SEM).

Remark

Pollen of Struthanthus is divers, including types very similar to that of Cladocolea, and types unique to the genus and similar to pollen of Peristethium leptostachyum. Noting the generic re-associations of species included in Cladocolea, Peristethium and Struthanthus, a final assessment regarding the pollen diversity of the genus will have to wait until comprehensive (regarding species coverage) molecular data becomes available.

Tripodanthus acutifolius (Ruiz et Pav.) Tiegh. (Figure 34)

Description

Pollen, distinctly oblate, concave-triangular in polar view, elliptic in equatorial view, equatorial apices truncated; size small, polar axis 6.7–8.3 µm long in LM, equatorial diameter 16.7–23.3 µm in LM, 14.3–20.4 µm in SEM; syn(3)colpate; exine 1.1–1.6 µm thick, nexine thinner than sexine, sexine thickened in area of mesocolpium, triangular intercolpial nexine thickenings in polar area (LM); tectate; sculpturing psilate in LM, micro-baculate to baculate in area of mesocolpium in SEM, bacula 0.6–1.4 µm long, 0.2–0.3 µm wide at base; margo well developed, widening in equatorial region, margo psilate (SEM).

Remark

Pollen Type B. Pollen of Tripodanthus acutifolius and T. flagellaris (Cham. et Schltdl.) Tiegh. (cf. Feuer & Kuijt 1980) is highly distinct within the Psittacanthinae lineage and Loranthaceae in general. Diagnostic features are the extremely oblate grains (can be more than three-times wide as high), the characteristic margo, and the long, densely packed bacula in the mesocolpium. Pollen of the third species, T. belmirensis, is figured in Roldán and Kuijt (2005), and seems to lack the diagnostic features (Table V; but see ‘Discussion’).

Lorantheae clade

The Lorantheae have four main clades, three of which (Amyeminae, Ileostylinae, Loranthinae) correspond to a single subtribe (Table I). The Lorantheae core clade (Clade J in Vidal-Russell & Nickrent 2008b) comprises the remaining subtribes (Dendrophthoinae, Emelianthinae, Scurrulinae, Tapinanthinae; Figures 2, 3, 7, 8). All Lorantheae pollen is of Type B. One of the most distinct pollen within the clade is the small, compact pollen of Loranthus, one of the two genera in the Loranthinae (the pollen of the second genus, Cecarria, is unknown). Pollen of Loranthus, like that of Plicosepalus (Tapinanthinae), can be heteropolar and distinctly bean-shaped in equatorial view. Heteropolar pollen grains are typically syncolpate on the proximal face and zonocolpate on the distal face. While most isopolar pollen grains are syncolpate, the other studied Tapinanthinae, which form a distinct subclade within the Lorantheae core clade, are typically zonocolpate (Figure 8). The only Emelianthinae with zonocolpate pollen is Moquiniella. Pollen outline of isopolar grains of the Lorantheae can be elliptic, emarginate, or rarely (Tapinanthus) subrhombic in equatorial view; in polar view the outlines range from straight-triangular (e.g. Loranthus) to trilobate. Several species/genera show the entire range from (slightly) convex-triangular to distinctly trilobate pollen (exemplified in Figures 7, 8). The equatorial apices are mostly obcordate but can also be T-shaped in several genera of the core Lorantheae (Agelanthus, Phragmanthera, Tapinanthus). A distinct margo, often psilate but in some taxa (partly) granulate, nano- or micro-verrucate, can be seen in most pollen except for Loranthus (Loranthinae), Helixanthera, and one of the Englerina species (core Lorantheae). In general, the structural elements are very small (≤ 0.5 µm); typically nano-verrucate to granulate, the mesocolpium of some Tapinanthinae (Agelanthus, Englerina, Oncocalyx and Tapinanthus) and Muellerina (Ileostylinae) shows nanoechini and nanobacula. Nanoverrucae are composed of conglomerate granula. A variable but common feature that can be seen under the LM and SEM (to some degree) is the thickening of (parts of) the exine (nexine and/or sexine) in the polar area, and an occasional thickening of the sexine in the mesocolpium at the equator. In overall appearance, the Lorantheae pollen cannot be confused with pollen of the Elytrantheae, Psittacantheae or the root-parasitic species. An exception may be the pollen of Muellerina, which is similar to that of Gaiadendron (Figure 11). Problematic may also be distinguishing between pollen of Aetanthus (Figures 22–24) and one type of Psittacanthus (Figure 33) with the echinate/baculate pollen of several core Lorantheae.

Amyeminae

Remark

So far, palynological data are only available for a single member of this Indomalayan-Australasian subtribe, which includes eight genera, seven for which molecular data are available.

Amyema gibberula Danser (Figure 35)

Open in a separate window

Figure 35.

LM (A) and SEM (B–I) micrographs of Amyema gibberula (from South Australia N. N. Donner, WU s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A, B, D, E), 1 µm (C, F–I).

Description

Pollen, distinctly oblate, concave-triangular in polar view, emarginate in equatorial view, equatorial apices obcordate; size small, polar axis 7.5–8.3 µm long in LM, equatorial diameter 20.8–24.2 µm in LM, 15.6–20.9 µm in SEM; syn(3)colpate, colpi widening towards apices and central polar area; exine 1.0–1.3 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM), sexine partly reduced in polar area, colpi widening to a small field (SEM); tectate; sculpturing psilate in LM, micro-verrucate to nano-verrucate and granulate in area of mesocolpium in SEM, verrucae 0.3–0.9 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate or partly granulate to nano-/micro-verrucate, margo with small triangular protrusions in polar area (SEM); colpus membrane nano-verrucate to nano-rugulate and granulate (SEM).

Remark

Pollen Type B. Pollen of Amyema shows features rarely or not found in any other Lorantheae, but shared with other Loranthaceae lineages. The colpi are widening towards the pole, where the sexine is partly reduced forming a shallow depression (as seen in the Ligarinae), reminiscent but not to be confused with an apocolpial field. The margo may show small triangular protrusions into the central polar area, analogue to what can be found in the Elytrantheae.

Dendrophthoinae

Remark

This tropical African-Indomalayan subtribe, forming a grade in molecular phylograms, includes four genera, of which three are studied genetically and palynologically. No data are available for the western Malaysian Trithecanthera. Pollen of the three studied genera is similar, with pollen grains of Helixanthera being most distinct (paralleling the molecular evidence, Figure 7).

Dendrophthoe pentandra (L.) Miq. (Figure 36)

Open in a separate window

Figure 36.

LM (A) and SEM (B–I) micrographs of Dendrophthoe pentandra (WU 0039138). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, concave-triangular to trilobate in polar view, elliptic in equatorial view, equatorial apices obcordate; size small, polar axis 13.3–15.0 µm long in LM, equatorial diameter 21.7–25.8 µm in LM, 20.5–26.7 µm in SEM; syn(3)colpate; exine 1.1–1.3 µm thick, nexine thinner than sexine (LM), sexine partly reduced in polar area, colpi widening to a small field (SEM); tectate; sculpturing psilate in LM, nano-verrucate and granulate in area of mesocolpium in SEM, verrucae 0.2–0.6 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate or partly granulate to nano-verrucate, margo with triangular protrusions in polar area (SEM); colpus membrane nano-verrucate, granulate (SEM). – Pollen Type B.

Helixanthera kirkii (Oliv.) Danser (Figure 37)

Open in a separate window

Figure 37.

LM (A) and SEM (B–I) micrographs of Helixanthera kirkii (WU: from Zambezi River, S.E. Africa, coll. Meryhart, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, concave-triangular in polar view, emarginate in equatorial view, equatorial apices obcordate; size small, polar axis 7.5–8.3 µm long in LM, equatorial diameter 20.0–24.2 µm in LM, 18.3–21.4 µm in SEM; syn(3)colpate; exine 1.0–1.3 µm thick, nexine thinner than sexine, triangular intercolpial nexine thickenings in polar area (LM), sexine partly reduced in polar area, colpi widening to a small field (SEM); tectate; sculpturing psilate in LM, nano-verrucate in area of mesocolpium in SEM, verrucae 0.2–0.6 µm in diameter, verrucae composed of conglomerate granula; margo indistinct, margo nano-verrucate, granulate or partly psilate, margo with triangular protrusions in polar area (SEM); colpus membrane nano-rugulate to nano-verrucate and granulate (SEM).

Remark

Pollen Type B. As in Amyema, the colpi widen towards the pole, where the sexine is partly reduced. This feature, which gives the pollen an emarginated outline in equatorial view, distinguishes it from that of the other two Dendrophthoinae. Another distinguishing feature is the indistinct margo of Helixanthera kirkii.

Tolypanthus maclurei (Merr.) Danser (Figure 38)

Open in a separate window

Figure 38.

LM (A) and SEM (B–I) micrographs of Tolypanthus maclurei (WU 039104). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate to straight-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size medium, polar axis 8.3–15.8 µm long in LM, equatorial diameter 25.0–30.0 µm in LM, 21.6–29.7 µm in SEM; syn(3)colpate; exine 0.8–1.3 µm thick, nexine thinner than sexine, triangular intercolpial nexine thickenings in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate and granulate in area of mesocolpium in SEM, verrucae 0.2–0.4 (–0.8) µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate or partly granulate, margo with triangular protrusions in polar area (SEM); colpus membrane nano-verrucate and granulate (SEM).

Remark

Pollen Type B. The pollen is nearly identical to that of Dendrophthoe pentandra.

Emelianthinae

Remark

The Emelianthinae form a distinct subclade within the Lorantheae. Palynological data are available for four out of the seven genera (Table IX). Except for Moquiniella, which is resolved as the first diverging lineage of the Emelianthinae (Figure 8), pollen is syncolpate. Pollen sculpturing is similar in all five species of the four studied genera, another shared feature is the thickening of the polar nexine (seen in LM).

Erianthemum dregei Tiegh. (Figure 39)

Open in a separate window

Figure 39.

LM (A) and SEM (B–I) micrographs of Erianthemum dregei (WU 039040). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, concave-triangular in polar view, slightly emarginate in equatorial view, equatorial apices obcordate; size small to medium, polar axis 6.7–15.0 µm long in LM, equatorial diameter 23.3–31.7 µm in LM, 24.2–30.6 µm in SEM; syn(3)colpate; exine 1.0–1.5 µm thick, nexine thinner than sexine, triangular intercolpial nexine thickenings in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate in area of mesocolpium in SEM, verrucae 0.2–0.6 µm in diameter; margo well developed, margo more distinct in equatorial regions, margo psilate or partly nano-verrucate to granulate, margo sometimes with small triangular protrusions in polar area (SEM); colpus membrane nano-verrucate and granulate (SEM). – Pollen Type B.

Globimetula dinklagei (Engl.) Danser (Figure 40)

Open in a separate window

Figure 40.

LM (A) and SEM (B–I) micrographs of Globimetula dinklagei (WU: from Cameroun, collector unknown, det. S. Balle, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, trilobate to concave-triangular in polar view, emarginate in equatorial view, equatorial apices obcordate; size medium, polar axis 15.0–18.3 µm long in LM, equatorial diameter 41.7–48.3 µm in LM, 39.1–45.3 µm in SEM; syn(3)colpate; exine 1.3–2.4 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area, sexine markedly thickened in area of mesocolpium (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.2–0.5 (−0.7) µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo micro-verrucate and partly granulate in polar area, margo psilate to partly granulate in equatorial regions (SEM); colpus membrane nano-verrucate and granulate (SEM).

Remark

Pollen Type B. Pollen of Globimetula is the largest pollen in Lorantheae and one of the largest pollen in the entire family: only pollen of Loxanthera (Elytrantheae) and some Psittacanthus (Psittacantheae: Psittacanthinae) are larger. A unique feature within the Lorantheae is the markedly thickened mesocolpial sexine.

Moquiniella rubra (A.Spreng.) Balle (Figure 41)

Open in a separate window

Figure 41.

LM (A) and SEM (B–I) micrographs of Moquiniella rubra (WU: origin and collector unknown, det. S. Balle, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, concave-triangular in polar view, slightly emarginate in equatorial view, equatorial apices obcordate; size medium, polar axis 15.0–17.5 µm long in LM, equatorial diameter 30.0–35.0 µm in LM, 27.1–32.9 µm in SEM; zono(3)colpate, colpi very long; exine 1.1–1.5 µm thick, nexine thinner than sexine, nexine thickened in central polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.2–0.5 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate (SEM).

Remark

Pollen Type B. This pollen differs from all other Emelianthinae pollen by being zonocolpate, a feature shared with other core Lorantheae.

Phragmanthera capitata (Spreng.) Balle (Figure 42)

Open in a separate window

Figure 42.

LM (A) and SEM (B–I) micrographs of Phragmanthera capitata (WU: from Cameroun, collector unknown, det. S. Balle, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate to concave-triangular in polar view, elliptic in equatorial view, equatorial apices T-shaped; size medium, polar axis 13.3–18.3 µm long in LM, equatorial diameter 25.0–30.0 µm in LM, 23.6–26.4 µm in SEM; syn(3)colpate; exine 1.1–1.6 µm thick, nexine thinner than sexine, triangular intercolpial nexine thickenings in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.2–0.5 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate or partly granulate, margo often with three large intercolpial sexine thickenings (irregular build-ups) in central polar area (SEM); colpus membrane nano-verrucate and granulate (SEM).

Remark

Pollen Type B. The irregular, intercolpial build-ups in the central polar area seen in SEM (Figure 42F) are unique within the family.

Note

Pollen surface features seen in the LM micrographs are not reflecting sculptural elements but cell contents and flower material, due to incomplete acetolisation. Fully processed grains had the tendency to rupture and lose their form, so we opted to interrupt the acetolising process for LM photography.

Phragmanthera rufescens (DC.) Balle (Figure 43)

Open in a separate window

Figure 43.

LM (A) and SEM (B–I) micrographs of Phragmanthera rufescens (WU: from Cameroun, collector unknown, det. S. Balle, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, concave-triangular in polar view, elliptic in equatorial view, equatorial apices T-shaped; size medium, polar axis 15.0–18.3 µm long in LM, equatorial diameter 26.7–31.7 µm in LM, 27.9–33.3 µm in SEM; syn(3)colpate; exine 1.1–1.4 µm thick, nexine thinner than sexine, triangular intercolpial nexine thickenings in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.1–0.6 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate or partly granulate (SEM); colpus membrane nano-verrucate and granulate (SEM).

Remark

Pollen Type B. The pollen of this species is very similar to that of Phragmanthera capitata except for the intercolpial, polar sexine build-ups in that species.

Note

Pollen surface features seen in the LM micrographs are not reflecting sculptural elements but cell contents and flower material, due to incomplete acetolisation. Fully processed grains had the tendency to rupture and lose their form, so we opted to interrupt the acetolising process for LM photography.

Ileostylinae

Remark

The Ileostylinae are a genetically distinct, but very small clade of Lorantheae with one monotypic genus in New Zealand, Ileostylus (not studied palynologically in detail; LM micrographs can be found in the Australasian Pollen and Spore Atlas at http://apsa.anu.edu.au), and the eastern Australian genus Muellerina, studied here for the first time using SEM.

Muellerina eucalyptoides (DC.) Barlow (Figure 44)

Open in a separate window

Figure 44.

LM (A) and SEM (B–I) micrographs of Muellerina eucalyptoides (MEL 2064534). A. Four pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A, B), 1 µm (C–I).

Description

Pollen, distinctly oblate, concave-triangular in polar view, elliptic to slightly emarginate in equatorial view, equatorial apices obcordate to broadly rounded; size small, polar axis 6.7–9.2 µm long in LM, equatorial diameter 15.8–18.3 µm in LM, 13.7–17.9 µm in SEM; syn(3)colpate; exine 1.1–1.5 µm thick, nexine thinner than sexine, nexine hexagonally thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-echinate to nano-baculate in area of mesocolpium in SEM, echini/bacula 0.3–0.6 µm long, 0.2–0.3 µm wide at base; margo well developed, margo striate to rugulate, striae/rugulae perpendicular to colpi; colpus membrane nano-verrucate to nano-echinate (SEM).

Remark

Pollen Type B. The pollen grains of Muellerina eucalyptoides from Australia are distinct from all other Lorantheae and remarkably similar to pollen grains of Gaiadendron punctatum (Gaiadendreae; Figure 11) and ‘Struthanthus’ mapirensis Rusby (a likely Gaiadendron; see ‘Discussion’) from South America. So far, only a single grain of Muellerina has been published in LM (Macphail et al. 2012). Another image can be found in the Australasian pollen and spore atlas (http://apsa.anu.edu.au). Both images match with our pollen in size and overall appearance.

Loranthinae

Remark

The Loranthinae include the Eurasian Loranthus with c. ten species, the only Loranthaceae extending into Europe, and the monotypic genus Cecarria (Philippines, New Guinea, New Britain, Solomon Islands), for which no palynological data are available.

Loranthus delavayi Tiegh. (Figure 45)

Open in a separate window

Figure 45.

LM (A) and SEM (B–I) micrographs of Loranthus delavayi (WU 039101). A. Two pollen grains in equatorial and polar view. B–C, E, F. Pollen grains in polar view. D. Pollen grain in oblique equatorial view. G. Close-up of central polar area. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A, B, F), 1 µm (C–E, G–I).

Description

Pollen, oblate, straight-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size small, polar axis 11.7–15.0 µm long in LM, equatorial diameter 20.5–25.0 µm in LM, 16.8–20.0 µm in SEM; syn(3)colpate (isopolar grains) or syn-/zono-(3)colpate, colpi very long (heteropolar grains); exine 1.1–1.7 µm thick, nexine thinner than sexine, triradial thickening of nexine in polar area, sexine markedly thickened in area of mesocolpium (LM); tectate; sculpturing psilate in LM, micro-verrucate and granulate, perforate, in area of mesocolpium in SEM, verrucae 0.4–1.1 µm in diameter; margo indistinct, margo micro-verrucate to psilate and partly granulate (SEM). – Pollen Type B.

Loranthus europaeus Jacq. (Figure 46)

Open in a separate window

Figure 46.

LM (A) and SEM (B–I) micrographs of Loranthus europaeus (WU 060561). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, straight-triangular in polar view, elliptic to slightly bean-shaped in equatorial view, equatorial apices obcordate; size small, polar axis 13.3–15.0 µm long in LM, equatorial diameter 20.0–23.3 µm in LM, 19.5–23.9 µm in SEM; syn-(3)colpate (isopolar grains) or syn-/zono-(3)colpate, colpi very long (heteropolar grains); exine 1.2–1.7 µm thick, nexine thinner than sexine, nexine thickened in polar area, sexine thickened in area of mesocolpium (LM); tectate; sculpturing psilate in LM, micro-verrucate and granulate, perforate in area of mesocolpium in SEM, verrucae 0.5–1.1 µm in diameter; margo indistinct, margo micro-verrucate and partly granulate; colpus membrane nano-verrucate to nano-rugulate and granulate (SEM).

Remark

Pollen Type B. The pollen of both species analysed here is very similar. Isopolar (elliptic in equatorial outline) and heteropolar grains (bean-shaped) can be found. Diagnostic features of the compact Loranthus pollen are the straight-triangular outline in polar view and thick walls compared to size (thickening of mesocolpial sexine and polar nexine).

Scurrulinae

Remark

A relatively large tribe with only two, but speciose genera: the east to southeast Asian Scurrula with 43 species; and the eastern African to tropical Asian Taxillus with c. 35 species (File S3). Pollen grains of the two genera figured so far and herein are very similar, and even using SEM it is impossible to differentiate between genera or species using pollen morphology. Notably all studied species show the entire range of (slightly) convex-triangular to trilobate pollen (polar view). They differ from other Lorantheae by their well-developed hexagonally thickened polar nexine (visible in LM). Grains are always nano=verrucate to granulate, both in the mesocolpium and colpus membrane. The margo is always very distinct and mostly psilate.

Scurrula parasitica L. (Figure 47)

Open in a separate window

Figure 47.

LM (A) and SEM (B–I) micrographs of Scurrula parasitica (WU 039110). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate to concave-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate to T-shaped; size small, polar axis 10.0–15.0 µm long in LM, equatorial diameter 18.3–25.0 µm in LM, 19.5–22.7 µm in SEM; syn-(3)colpate; exine 1.1–1.3 µm thick, nexine thinner than sexine, nexine thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.1–0.5 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate or partly nano-verrucate (SEM); colpus membrane nano-verrucate and granulate (SEM). – Pollen Type B.

Taxillus aldabrensis (Turill) Danser (Figure 48)

Open in a separate window

Figure 48.

LM (A) and SEM (B–I) micrographs of Taxillus aldabrensis (WU: from Madagascar, coll. J. M. Hildebrandt, s.n.). A. Three pollen grains in polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate in polar view, elliptic in equatorial view, equatorial apices obcordate to T-shaped; size small to medium, polar axis 13.5–15.6 µm long in LM, equatorial diameter 25.0–28.3 µm in LM, 21.3–31.4 µm in SEM; syn-(3)colpate; exine 1.0–1.3 µm thick, nexine thinner than sexine, nexine thickened in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.1–0.5 µm in diameter, verrucae composed of conglomerate granula; margo well developed, most pronounced at apices, margo psilate with few nanoverrucae or granula in polar area (SEM); colpus membrane nano-verrucate and granulate (SEM). – Pollen Type B.

Taxillus caloreas (Diels) Danser (Figure 49)

Open in a separate window

Figure 49.

LM (A) and SEM (B–I) micrographs of Taxillus caloreas (WU 039396). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H. Close-up of mesocolpium. I. Close-up of apex and mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, concave-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size small to medium, polar axis 11.7–15.0 µm long in LM, equatorial diameter 23.3–30.0 µm in LM, 21.1–26.0 µm in SEM; syn-(3)colpate; exine 1.0–1.3 µm thick, nexine thinner than sexine, hexagonal nexine thickening in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.1–0.5 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate with few nanoverrucae or granula in polar area (SEM); colpus membrane nano-verrucate and granulate (SEM). – Pollen Type B.

Taxillus delavayi (Tiegh.) Danser (Figure 50)

Open in a separate window

Figure 50.

LM (A) and SEM (B–I) micrographs of Taxillus delavayi (WU 039090). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, trilobate to concave-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size small to medium, polar axis 10.0–13.3 µm long in LM, equatorial diameter 21.7–26.7 µm in LM, 18.9–27.8 µm in SEM; syn-(3)colpate; exine 1.0–1.3 µm thick, nexine thinner than sexine, hexagonal nexine thickening in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.1–0.4 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate with few nanoverrucae or granula, margo sometimes with triangular protrusion in polar area (SEM); colpus membrane nano-verrucate and granulate (SEM). – Pollen Type B.

Tapinanthinae

Remark

The African-Arabian Tapinanthinae represents the largest subtribe of the Lorantheae with 14 genera and more than 170 species (File S3). We here present the first palynological data on six genera (13 species). Table X includes also information on two additional (Madagascan) genera based on grains figured in Muller et al. (1989).

Actinanthella menyhartii (Engl. et Schinz ex Schinz) Balle (Figure 51)

Open in a separate window

Figure 51.

LM (A) and SEM (B–I) micrographs of Actinanthella menyhartii (WU 0029707). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, trilobate to concave-triangular in polar view, emarginate in equatorial view, equatorial apices obcordate; size medium, polar axis 10.0–15.0 µm long in LM, equatorial diameter 25.0–30.0 µm in LM, 22.4–29.1 µm in SEM; zono-(3)colpate, colpi very long; exine 1.1–1.5 µm thick, nexine thinner than sexine, nexine thickened in central polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.2–0.5 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate with few microverrucae (SEM).

Remark

Pollen Type B. The grains differ from the other zonocolpate members of the Tapinanthinae (Agelanthus, Englerina, Oncocalyx) by their nano-verrucate to granulate sculpturing and the occurrence of modified trilobate pollen (Figure 51A, lower grain; Figure 51C, E).

Agelanthus brunneus (Engl.) Tiegh. (Figure 52)

Open in a separate window

Figure 52.

LM (A) and SEM (B–I) micrographs of Agelanthus brunneus (WU 039037). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, straight-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size medium, polar axis 10.8–18.3 µm long in LM, equatorial diameter 28.3–36.7 µm in LM, 31.4–35.7 µm in SEM; zono-(3)colpate, colpi very long; exine 1.0–1.5 µm thick, nexine thinner than sexine, nexine thickened in central polar area (LM); tectate; sculpturing psilate in LM, nano-/micro-echinate to nano-/micro-baculate and granulate in area of mesocolpium in SEM, echini/bacula 0.3–0.9 µm long, 0.2–0.4 µm wide at base (SEM); margo well developed, widening in equatorial region, margo psilate (SEM); exine in central polar area protruding forming a small dome (SEM). – Pollen Type B.

Note

Pollen surface features seen in the LM micrographs are not reflecting sculptural elements but cell contents and flower material, due to incomplete acetolisation. Fully processed grains had the tendency to rupture and lose their form, so we opted to interrupt the acetolising process for LM photography.

Agelanthus discolor (Schinz) Balle [= Tapinanthus discolor (Schinz) Danser] (Figure 53)

Open in a separate window

Figure 53.

LM (A) and SEM (B–I) micrographs of Agelanthus discolor (WU 039038). A. Two pollen grains, one in equatorial and polar view, other in polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate to concave-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size medium, polar axis 16.7–18.3 µm long in LM, equatorial diameter 26.7–33.3 µm in LM, 23.0–26.5 µm in SEM; zono-(3)colpate, colpi very long; exine 1.1–1.5 µm thick, nexine thinner than sexine, nexine thickened in central polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium and central polar area in SEM, verrucae 0.3–0.6 µm in diameter, verrucae composed of conglomerate granula; margo fairly well developed, margo psilate to nano-verrucate (SEM); colpus membrane granulate (SEM).

Remark

Pollen Type B. The species used to be included in the genus Tapinanthus (Tropicos.org 2016), but it belongs into Agelanthus (anonymous reviewer, personal communication, 2016). The pollen is indeed distinct from the unique pollen in the other two species of Tapinanthus (T. bangwensis, T. ogowensis). More similar to the pollen of its new congeners, it differs from the pollen of the two other Agelanthus species by its sculpturing. However, it resembles strongly the pollen of Oncocalyx, which is resolved as a close relative of Agelanthus based on the limited molecular data available so far for African Loranthaceae (Figures 2, 3; Su et al. 2015).

Agelantus scassellatii (Chiov.) Polhill et Wiens (Figure 54)

Description

Pollen, oblate, straight-triangular to concave-triangular in polar view, elliptic in equatorial view, equatorial apices T-shaped; size medium, polar axis 11.7–20.0 µm long in LM, equatorial diameter 26.7–35.0 µm in LM, 27.7–32.0 µm in SEM; zono-(3)colpate, colpi very long; exine 1.1–1.5 µm thick, nexine thinner than sexine, nexine thickened in central polar area (LM); tectate; sculpturing psilate in LM, nano-echinate to nano-baculate and granulate in area of mesocolpium in SEM, echini/bacula 0.2–0.6 µm long, 0.2–0.3 µm wide at base (SEM); margo well developed, widening in equatorial region, margo psilate with few nanoechini/bacula (SEM); exine in central polar area protruding forming a small dome (SEM).

Remark

Pollen Type B. Pollen of both Agelanthus bruneus and A. scassellatii are very similar. The only difference is that the equatorial apices are often T-shaped in A. scassellatii. A diagnostic feature of both species is the minute, protruding dome seen at the pole, at the junction of the colpi (SEM; Figures 52B–E, 54B–F).

Note

Pollen surface features seen in the LM micrographs are not reflecting sculptural elements but cell contents and flower material, due to incomplete acetolisation. Fully processed grains had the tendency to rupture and lose their form, so we opted to interrupt the acetolising process for LM photography.

Englerina holstii (Engl.) Tiegh (Figure 55)

Open in a separate window

Figure 54.

LM (A) and SEM (B–I) micrographs of Agelantus scassellatii (WU 004299). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, distinctly oblate, straight-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size medium, polar axis 11.7–13.3 µm long in LM, equatorial diameter 33.3–36.7 µm in LM, 27.7–34.8 µm in SEM; zono-(3)colpate, colpi very long; exine 1.2–1.5 µm thick, nexine thinner than sexine (LM); tectate; sculpturing psilate in LM, nano-/micro-verrucate to nano-/micro-echinate and granulate in area of mesocolpium in SEM, verrucae/echini 0.2–0.9 µm long, 0.1–0.5 µm wide at base (SEM); margo indistinct, widening in equatorial region, margo nano-/micro-verrucate to nano-/micro-echinate and granulate in polar area, margo psilate in equatorial region (SEM); exine in central polar area protruding forming a small dome (SEM). – Pollen Type B.

Englerina oedostemon (Danser) Polhill et Wiens (Figure 56)

Open in a separate window

Figure 55.

LM (A) and SEM (B–I) micrographs of Englerina holstii (WU: from East Africa, coll. J. Brunnthaler, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate to concave-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size small to medium, polar axis 16.7–21.7 µm long in LM, equatorial diameter 23.3–26.7 µm in LM, 18.5–24.7 µm in SEM; zono-(3)colpate, colpi very long; exine 1.3–1.5 µm thick, nexine thinner than sexine, nexine thickened in central polar area (LM); tectate; sculpturing psilate in LM, micro-echinate to nano-echinate and granulate in area of mesocolpium and central polar area in SEM, echini 0.3–0.9 µm long, 0.2–0.4 µm wide at base (SEM); margo well developed, margo psilate with few microechini (SEM); exine in central polar area protruding slightly (SEM).

Remark

Pollen Type B. Regarding shape, outlines in equatorial and polar views, Englerina holstii is much more similar to Agelanthus than Englerina oedostemon. Regarding sculpturing the opposite is true. The grains differ from those of the putative sister genus of Englerina, Tapinanthus.

Oncocalyx schimperi (Hochst. ex A.Rich.) M.G.Gilbert (Figure 57)

Open in a separate window

Figure 56.

LM (A) and SEM (B–I) micrographs of Englerina oedostemon (WU: from Zimbabwe, collector unknown, det. W. Frostreder[?], s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, straight-triangular to concave-triangular in polar view, slightly emarginate in equatorial view, equatorial apices obcordate; size medium, polar axis 11.7–21.7 µm long in LM, equatorial diameter 28.3–36.7 µm in LM, 23.9–34.3 µm in SEM; zono-(3)colpate, colpi very long; exine 1.1–1.5 µm thick, nexine thinner than sexine (LM); tectate; sculpturing psilate in LM, nano-verrucate to nano-echinate and granulate in area of mesocolpium in SEM, verrucae/echini 0.2–0.5 µm long, 0.2–0.5 µm wide at base, verrucae/echini composed of conglomerate granula; margo well developed, margo psilate and partly nano-verrucate/echinate to granulate (SEM). – Pollen Type B.

Note

Pollen surface features seen in the LM micrographs are not reflecting sculptural elements but cell contents and flower material, due to incomplete acetolisation. Fully processed grains had the tendency to rupture and lose their form, so we opted to interrupt the acetolising process for LM photography.

Oncocalyx welwitschii (Engl.) Polhill et Wiens (Figure 58)

Open in a separate window

Figure 57.

LM (A) and SEM (B–I) micrographs of Oncocalyx schimperi (WU 037621). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, straight-triangular to concave-triangular in polar view, elliptic to rhombic in equatorial view, equatorial apices obcordate; size medium, polar axis 11.7–18.3 µm long in LM, equatorial diameter 25.0–31.7 µm in LM, 26.1–30.3 µm in SEM; zono-(3)colpate, colpi very long; exine 1.0–1.3 µm thick, nexine thinner than sexine, nexine thickened in central polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate to granulate in area of mesocolpium in SEM, verrucae 0.3–0.6 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate; colpus membrane granulate (SEM).

Remark

Pollen Type B. Being very similar in general appearance, the sculpturing elements are as a trend larger in Oncocalyx welwitschii and O. schimperi. The general type is shared with the other taxa with zonocolpate grains (Agelanthus, Actinanthella; Figures 51–54), resolved as close relatives Oncocalyx based on molecular data (Figure 8).

Plicosepalus acaciae (Zucc.) Wiens et Polhill (Figure 59)

Open in a separate window

Figure 58.

LM (A) and SEM (B–I) micrographs of Oncocalyx welwitschii (WU 039064). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate to straight-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size small to medium, polar axis 16.7–20.0 µm long in LM, equatorial diameter 23.3–28.3 µm in LM, 19.5–25.5 µm in SEM; syn-(3)colpate; exine 1.1–1.5 µm thick, nexine thinner than sexine (LM); tectate; sculpturing psilate in LM, micro-verrucate to nano-verrucate and granulate in area of mesocolpium in SEM, verrucae 0.2–0.7 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo segmented perpendicular to colpi (SEM); colpus membrane nano-verrucate and granulate (SEM). – Pollen Type B.

Note

Pollen surface features seen in the LM micrographs are not reflecting sculptural elements but cell contents and flower material, due to incomplete acetolisation. Fully processed grains had the tendency to rupture and lose their form, so we opted to interrupt the acetolising process for LM photography.

Plicosepalus curviflorus (Benth. ex Oliv.) Tiegh (Figure 60)

Open in a separate window

Figure 59.

LM (A) and SEM (B–I) micrographs of Plicosepalus acacia (WU: from Palestine, coll. H. Boyko, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate to concave-triangular in polar view, elliptic in equatorial view, equatorial apices obcordate; size small, polar axis 11.7–15.0 µm long in LM, equatorial diameter 20.0–25.0 µm in LM, 18.1–21.6 µm in SEM; syn-(3)colpate; exine 0.9–1.3 µm thick, nexine thinner than sexine, triradial nexine thickening in polar area (LM); tectate; sculpturing psilate in LM, nano-verrucate and granulate in area of mesocolpium in SEM, verrucae 0.1–0.4 µm in diameter, verrucae composed of conglomerate granula; margo well developed, margo psilate to weakly micro-rugulate (SEM); colpus membrane granulate (SEM).

Remark

Pollen Type B. Pollen of Plicosepalus curviflorus match those of P. acaciae in most features. A striking dissimilarity is the coarsely segmented margo of P. acaciae (Figure 59G), not found in any other Lorantheae.

Plicosepalus sagittifolius (Engl.) Danser (Figure 61)

Open in a separate window

Figure 60.

LM (A) and SEM (B–I) micrographs of Plicosepalus curviflorus (WU: from Kenya, coll. J. B. Gillett, s.n.). A. Two pollen grains in equatorial and polar view. B–E. Pollen grains in polar view. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, heteropolar, oblate, concave-triangular in polar view, bean-shaped in equatorial view, equatorial apices obcordate; size medium, polar axis 16.7–20.0 µm long in LM, equatorial diameter 28.3–31.7 µm in LM, 23.8–27.3 µm in SEM; syn-(3)colpate on proximal side, zono-(3)colpate on distal side, colpi very short on distal side; exine 1.1–1.8 µm thick, nexine thinner than sexine, nexine markedly thickened in polar areas (LM); tectate; sculpturing psilate in LM, sculpturing elements in area of mesocolpium varying in size on proximal vs. distal side of grains under SEM, distal side verrucate and granulate, verrucae on distal side 0.5–1.2 µm in diameter, proximal side nano-verrucate and granulate, verrucae on proximal side 0.1–0.4 µm in diameter, verrucae decreasing in density from proximal to distal polar area, verrucae composed of conglomerate granula; margo well developed, margo psilate (SEM); colpus membrane nano-verrucate to granulate (SEM).

Remark

Pollen Type B. In constrast to the other two species (Plicosepalus acaciae, P. curviflorus), grains of P. sagittifolius are heteropolar. The only other Lorantheae so far with heteropolar grains is Loranthus, which has heteropolar and isopolar grains. A further characteristic feature of P. sagittifolius is the gradual change seen in the size and density of sculptural elements on the proximal vs. distal side (Figure 61F, I).

Tapinanthus bangwensis (Engl. et K.Krause) Danser (Figure 62)

Open in a separate window

Figure 61.

LM (A) and SEM (B–I) micrographs of Plicosepalus sagittifolius (WU: from Kenya, coll. M. G. Gilbert, s.n.). A. Two pollen grains in equatorial and polar view. B, C. Pollen grains in polar view, distal side. D. Pollen grain in polar view, proximal side. E. Pollen grain in equatorial view. F. Close-up of central polar area, distal side. G. Close-up of apex, distal side. H. Close-up of central polar area, proximal side. I. Close-up of mesocolpium. Scale bars – 10 µm (A–E), 1 µm (F–I).

Description

Pollen, oblate, trilobate in polar view, elliptic to (sub)rhombic in equatorial view, equatorial apices T-shaped; size medium, polar axis 20.0–25.0 µm long in LM, equatorial diameter 35.0–40.0 µm in LM, 32.7–35.5 µm in SEM; demisyn-(3)colpate, colpi very short, tapering towards pole and equator; exine 1.2–1.5 µm thick, nexine thinner than sexine, nexine hexagonally thickening in polar area (LM); tectate; sculpturing psilate in LM, nano-/micro-echinate to nano-/micro-baculate and granulate in area of mesocolpium in SEM, echini/bacula 0.3–0.8 µm long, 0.3–0.5 µm wide at base; margo well developed, very broad in equatorial area, margo psilate with very few nano-/micro-echini or nano-/micro-bacula, margo with triangular protrusion in central polar area (SEM); colpus membrane nano-verrucate and granulate (SEM).

Remark

Pollen Type B. This pollen shows a unique feature not seen in any other Loranthaceae so far. The margo is extremely broad and well developed, covering most of the polar surface, and is distinctly flattened, not inflated/roundish or indistinct as in other Loranthaceae. It is also the only Lorantheae pollen with demisyncolpate apertures.

Tapinanthus ogowensis (Engl.) Danser

(Figure 63)

Open in a separate window

Figure 62.

LM (A) and SEM (B–I) micrographs of Tapinanthus bangwensis (WU: from Liberia, collector unknown, WU s.n.). A. Two pollen grains in equatorial and polar view. B–D. Pollen grains in polar view. E. Close-up of colpus and membrane. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–D), 1 µm (E–I).

Open in a separate window

Figure 63.

LM (A) and SEM (B–I) micrographs of Tapinanthus ogowensis (WU: from Cameroun, collector unknown, det. S. Balle, s.n.). A. Two pollen grains in equatorial and polar view. B–D. Pollen grains in polar view. E. Close-up of colpus and membrane. F. Close-up of central polar area. G. Close-up of apex. H, I. Close-ups of mesocolpium. Scale bars – 10 µm (A–D), 1 µm (E–I).

Description

Pollen, oblate, trilobate in polar view, elliptic to (sub)rhombic in equatorial view, equatorial apices T-shaped; size medium, polar axis 23.3–26.7 µm long in LM, equatorial diameter 40.0–45.0 µm in LM, 34.3–42.1 µm in SEM; demisyn-(3)colpate, colpi very short, tapering towards pole and equator; exine 1.3–1.6 µm thick, nexine thinner than sexine, nexine hexagonally thickening in polar area, sexine thickened in area of mesocolpium (LM); tectate; sculpturing psilate in LM, nano-/micro-echinate to nano-/micro-baculate and granulate in area of mesocolpium in SEM, echini/bacula 0.3–1.0 µm long, 0.2–0.3 µm wide at base; margo well developed, very broad in equatorial area, margo psilate with very few nano-/micro-echini or nano-/micro-bacula, margo with triangular protrusion in central polar area (SEM); colpus membrane nano-verrucate and granulate (SEM).