The Geological History of Tropical Rainforests 

Tropical rainforests are the most structurally complex and diverse land ecosystems on Earth. The fossil record of leaves indicates that they have a history stretching at least to the Paleocene (~58 million years ago) (Wing et al. 2009; PNAS, 106:18627–18632), and the fossil record of pollen and spores has been used to show that Neotropical plant diversity is sensitive to global temperature (Jaramillo et al. 2006; Science, 311, 1893–1896), and that the end-Cretaceous mass extinction event reduced Neotropical plant diversity by 45% (Carvalho et al. 2021; Science, 372, 63–68).

At present there is a lack of fossil data on the evolutionary history of rainforests in the Old World tropics, particularly in West Africa. In order to address this gap I am working with collaborators to undertake primary descriptive taxonomic work on fossil pollen and spores from Nigeria, and palaeoecological work on the diversity and composition of fossil assemblages in order to understand the geological history of rainforests in this region. Our work so far has focussed on the Paleocene–Eocene of the northern Niger Delta, and has resulted in the redescription of existing taxa (see figure to the right), and the description of new genera and species. Such taxonomic work provides the foundation for reconstructing plant biodiversity in the geological past, and will facilitate studies of the biogeographical evolution of rainforests using plant fossils.   

Pollination Biology in Tropical Rainforests

The transfer of pollen grains from male to female reproductive apparatus is a critical part of plant reproduction that produces seeds and a new generation. The process of pollination ultimately sustains plant populations, and the interactions between plants and their pollinators represent complex interaction networks that have been called the architecture of biodiversity (Bascompte & Jordano 2007; Annual Review of Ecology Evolution and Systematics, 38, 567–593).

However, very little is known about pollination in tropical rainforests. Partly this reflects a lack of research on the topic, but also reflects the difficulty of obtaining data on plants that flower infrequently and have flowers that are largely inaccessible in the canopy. We are focussing our efforts on the flora of Barro Colorado Island, Panama, and our results so far have shown that the pollen grains of biotically pollinated plants are more morphologically diverse than those of abiotically pollinated plants (see figure to the left). This provides a potential link between pollination ecology and pollen morphology that we are currently investigating further.