SEM | Ecology of the past

Wei, C. (2023) Morphometrics of modern and fossil Poaceae pollen from South America. PhD Thesis, University of Amsterdam, Amsterdam. ISBN:

Abstract

Poaceae (the grass family) is one of the most diverse angiosperm families on Earth, comprising close to 12,000 species. The history of grass-dominated biomes extends back over 20 million years, yet the spatial and temporal development of these biomes and the underlying drivers remains unresolved. This thesis addresses these questions in South America, focusing on modern grass pollen and ancient samples dating from the early Miocene to the present. The thesis reveals several key points: (i) Grass pollen size varies significantly both among genera and species and within species. Pollen size shows no correlation with (a)biotic factors, indicating its limited utility as a generally applicable proxy for reconstructing past vegetation and climate; (ii) Grass pollen exhibits high diverse on surface ornamentation. The morphotypes identified by descriptive terminology are well-supported by a combination of SEM images of pollen surface patterns and computational image analysis. The findings reveal that pollen sculpture is unrelated to (a)biotic variables but is diverse across the phylogeny; (iii) Tropical grass pollen morphology suggests a gradual rather than punctuated evolution, based on the trend toward a less dense ornamentation of the exine since c. 23 Ma. The changes in the exine of grass pollen since the early Miocene might be driven by evolutionary processes (evolutionary drift and/or directional selection), and potentially immigration at the continental scale. In summary, the thesis reveals the trajectory of grass pollen morphological changes over time and examining the drivers that have contributed to their evolution and geographical expansion at the continental scale.

Handle: http://hdl.handle.net/11245.1/1f4f5550-1069-423a-ace3-2192ac4160c6

Guest post by Dr. Lynne Quick (Nelson Mandela University Palaeoecology Laboratory)

The primary focus of the new state-of-the-art palaeoecology laboratory at Nelson Mandela University is to conduct palynological studies, with a strong geographic emphasis on the Cape south coast and the Cape Floristic Region in general. While our initial and primary focus will be on pollen analysis, our overarching goal is to establish a highly versatile open science resource-base for palaeoscience research at Nelson Mandela University.

Head of Laboratory: Dr Lynne Quick

Lynne Quick is a Senior Research Fellow associated with the African Centre for Coastal Palaeoscience at Nelson Mandela University. She is a palynologist with interests in palaeoecology and palaeoclimatology. She is working on the development of new palaeoenvironmental records in southern Africa and has a key focus on the vegetation history and past climate dynamics of the Cape Floristic Region. Lynne is the President of the Southern African Society for Quaternary Research (SASQUA), a Vice President of the International Union for Quaternary Research (INQUA) and a member of the scientific steering committee of the AFQUA (African Quaternary: Environments, Ecology and Humans) initiative. [Email: lynne.j.quick@gmail.com |Twitter: @drljquick]

Senior Laboratory Technician: Ms Erin Hilmer

Erin Hilmer completed an undergraduate BSc degree at Nelson Mandela University followed by an honours in geology at the University of Stellenbosch. In addition to her role as the Senior Laboratory Technician of the new palaeolab, she manages Port Elizabeth’s only pollen and spore trap and generates weekly pollen and spore data for the city. This work forms part of a national monitoring network (www.pollencount.co.za). She also has expertise in geochronology and scanning electron (SEM) microscopy.