J Syst Evol

• Research Article •    

Grass pollen surface ornamentation is diverse across the phylogeny: Evidence from northern South America and the global literature

Cai-Xia Wei1*, Phillip E. Jardine2, Li-Mi Mao3, Luke Mander4, Mao Li5, William D. Gosling1, and Carina Hoorn1   

  1. 1 Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands;
    2 Institute of Geology and Palaeontology, University of Münster, Münster, Germany;
    3 The State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China;
    4 Department of Environment, Earth and Ecosystems, The open University, Milton Keynes, UK;
    5 Donald Danforth Plant Science Center, Saint Louis, MI, USA
    *Author for correspondence. Caixia Wei. E-mail:caixiawei1994@gmail.com
  • Received:2023-03-24 Accepted:2023-08-21 Online:2023-09-27

Abstract: The grasses are one of the most diverse plant families on Earth. However, their classification and evolutionary history are obscured by their pollen stenopalynous (similar) morphology. A combination of high-resolution imaging of pollen surface ornamentation and computational analysis has previously been proposed as a promising tool to classify grass taxonomic boundaries. In this study, we test this hypothesis by studying Poaceae pollen across the phylogeny from plants collected in northern South America and also from published literature across the globe. We assessed if morphotypes that we establish using descriptive terminology are supported by computational analysis, if they vary along six (a)biotic variables and vary across the phylogeny. Based on this analysis, we constructed a reference framework for pollen surface ornamentation morphotypes. Our results showed that there is a wide variation of grass pollen surface ornamentation. We identified nine new and confirmed six known morphotypes, establishing a data set for 223 species (243 individual plant specimens) that represent 11 subfamilies. Computational analysis showed that our morphotypes are well-supported by two quantitative features of pollen sculptural elements (size and density). The specific data set and mapping of the phylogeny confirmed that pollen morphological sculpture is unrelated to (a)biotic variables and is diverse across the phylogeny.

Key words: computational analysis, exine, grass, phylogeny, pollen morphology, quantitative analysis