Pollen morphology of extant Winteraceae: a study allowing SEM-based affiliation of its fossil representatives

Abstract

ABSTRACT. When applying high-resolution microscopy, the pollen morphology of extant taxa can be used to classify fossil pollen, that is, to address the latter in the established systematic-phylogenetic framework. Here we investigate tetrads and pollen features of 20 different Winteraceae species, most of them belonging to the early-diverging generic lineages Tasmannia, Drimys and Pseudowintera. The tetrads and pollen are grouped into eleven pollen types based on diagnostic features observed by both light and scanning electron microscopy. The high-resolution scanning electron micrographs of recent material allow detailed comparison with fossil material, resulting in a more accurate affiliation of fossil tetrads/pollen to extant lineages. As a case study, early Miocene Winteraceae tetrads from South Africa are re-examined and formally described. The systematic placement of the African fossils is discussed in light of the pollen types presented here.

A Winteraceae pollen tetrad from the early Paleocene of western Greenland, and the fossil record of Winteraceae in Laurasia and Gondwana

“…Pseudowinterapollis pollen so far has mostly been studied with LM, except for Miocene tetrads from South Africa (cf. Grímsson et al., ). The unique pollen morphology of Winteraceae, however, allows us to confidently place our Greenland material in this family (next section) and in the genus Pseudowinterapollis , albeit not in any of the previously described species.…”

“…We also compared our new species to three low‐ to mid‐latitude African–Arabian pollen fossils studied with SEM (Table , Appendix S3), namely Pseudowinterapollis africanensis Grímsson, F.H. Neumann & Zetter from the Miocene of Noordhoek on the Cape Peninsula (Coetzee & Praglowski, ; Grímsson et al., ; Neumann et al., ; Roberts et al., ), Qatanipollis species from the Albian of Israel (Schrank, ; Walker, Brenner, & Walker, ); and Walkeripollis gabonensis J.A.Doyle, Hotton & J.V.Ward from the late Barremian to early Aptian of Gabon, equatorial western Africa (Doyle et al., ). Of these, P. agatdalensis shares the most (overlapping) features with the ~40 Myr younger tetrads from South Africa, whereas the ~50 or 65 Myr older African and Near Eastern fossils differ by a least half of the major traits (Table ; Appendix S3).…”

“…The fossil pollen tetrad from Greenland shows the complete character suite of (modern) Winteraceae (Table ; cf. Grímsson et al., for details), namely a persistent tetrad composed of clearly ulcerate pollen grains with a distinct reticulate sculpturing and lacking tectal connections between the individual grains (acalymmate). Grímsson et al.…”

“…Additional close‐ups display the characteristic SEM sculpturing of the pollen/tetrad surface (Appendix S2). The fossil pollen tetrad was compared to all previously published Winteraceae pollen tetrads, to fossil tetrads from the Miocene of South Africa (re‐studied using SEM), and new herbarium material (Grímsson et al., ) from the University of Vienna (WU), the Natural History Museum of Vienna (W), the Missouri Botanical Garden (MO), the Herbaria of Munich (M and MSB), the Allan Herbarium (CHR) and the Museum of New Zealand (WELT) (Appendix S3). The preparation of extant material follows the procedures outlined in Grímsson et al.…”

“…One genus ( Drimys ) occurs in South America and another ( Takhtajania ) in Madagascar (Thomas, Bruhl, Ford, & Weston, ). Winteraceae are evergreen shrubs or small trees that completely lack xylem vessels (Feild, Zwieniecki, & Holbrook, ; Poole & Francis, ) and that have a unique type of pollen/tetrad (Grímsson, Xafis, Neumann, & Zetter, ). The family has an extensive fossil record back to the Cretaceous in both the Northern and Southern Hemispheres (Figure , Appendix S1 in Supporting Information).…”