My research focuses on the interchange between ecology and evolution from micro to macro levels, to understand the global distribution of taxonomic, genetic, functional and phylogenetic diversity. Understanding these patterns and the processes causing them is important for conservation and predicting what may happen to ecosystems in the future. I test the (historical) influence of functional (ecological) traits, climate, vegetation types and biotic interactions on population dynamics and diversification rates, and how this varies among regions and biomes. To do so, I integrate phylogenetic, population genomic, environmental, and fossil data, and use a range of phylogenetic comparative methods, linear statistics, and historical demographic models to test specific predictions and hypotheses. Some examples of this research are outlined below. Please contact me for potential student projects.
A juicy topic: fruit traits, diversification rates, and the evolution of tropical rain forest diversity
Frugivory, Brazil
Frugivory (i.e. fruit-eating and seed dispersal by animals) is ubiquitous in tropical ecosystems, but the role that frugivores have played in the macroevolution of species-rich tropical plant families remains largely unexplored. Questions we address are: How are plant traits relevant to frugivory (e.g. fruit size, fruit color, fruit shape, understory/canopy growth form, etc.) distributed within the angiosperm tree of life? Do these traits influence diversification rates? How does the evolution and spatial occurrence of these traits coincide with the global biogeographic distribution of vertebrate frugivores (birds, bats, primates, other frugivorous mammals) and their ecological traits (e.g. diet specialization, body size, flight ability, etc.)? What is the effect of (extinct) megafauna on the diversification, evolution and connectivity of populations and species? Angiosperm lineages that I particularly focus on to assess these questions are Annonaceae, Arecaceae and Fabaceae (Mimosoideae), and focal areas include Madagascar and the Neotropics, but I often apply a global framework to be able to assess evolutionary differences between biogeographical realms.
I started this work during my postdoc in the Sauquet lab at the Université Paris-Sud (funded by the Early Postdoc.Mobility fellowship of the Swiss National Science Foundation, Aug 2015-May 2016). This project was in collaboration with Daniel Kissling, Hélène Morlon, Thomas Couvreur, Lars Chatrou and Hervé Sauquet, to study “Frugivory, functional traits and the diversification of a tropical angiosperm family: Annonaceae (Magnoliales)”. For a 1 minute summary of the project- watch this video. I continued this work in the Biogeography and Macroecology (BIOMAC) group at the Institute for Biodiversity and Ecosystem Dynamics (IBED) at the University of Amsterdam (June 2016-May 2018), together with Daniel Kissling, Bill Baker, Jens-Christian Svenning, Thomas Couvreur, among others. I have continued this research line at the German Centre for Integrative Biodiversity Research (iDiv) where I am leading the ‘Evolution and Adaptation‘ research group and at Naturalis Biodiversity Center.
Global convergence and the evolution of diversity and functional traits across biomes – with a special focus on mediterranean-type ecosystems
the Cape, South Africa
I am interested in understanding the causes of the extraordinary (taxonomic and functional) richness of angiosperms in particular biomes and ecosystems, and how unique features/innovations, or ‘traits’ may have allowed the colonisation, diversification dynamics and persistence in these systems. For example, mediterranean-type ecosystems (MTEs) – i.e. the Cape, Western Australia, California, the Mediterranean Basin and Chile – are all classified as biodiversity hotspots and comprise such extraordinary diversity. I specifically study how vegetative functional traits (e.g. sclerophyllous leaves, spinescence) have evolved, and which processes may underlie patterns of convergence or non-convergence between MTEs. Furthermore, I am interested in how these traits may have interacted with the abiotic environment (climatic niches) in which lineages have evolved, and how this interaction could have influenced speciation and extinction rates, and thus species-richness in these systems. My main focal clades are Proteaceae, Rhamnaceae, and the Cape Penaeaceae and Diosmeae. I am expanding this research line to other biomes, such as succulent systems, rainforests, and seasonally dry tropical forests, to further understand the conditions under which convergence and radiations happen, specifically focusing on (mimosoid) legumes. To do so, we are assembling a large mimosoid legume trait database in collaboration with the Legume Working Group (main collaborators: Colin Hughes, Jens Ringelberg).
Why are there so many species of flowering plants?
Phylica sp.
Darwin’s second ‘abominable mystery’ targets the question why flowering plants (angiosperms) are so species-rich and ecologically successful, in particular compared to other plant clades (e.g. pteridophytes and gymnosperms). Crepet and Niklas (2009) discussed the influence of mutually beneficial animal–plant relationships (e.g. dispersal and pollination), and the intrinsic ‘adaptability’ of angiosperms as possible explanations for angiosperm success. I aim to quantify Crepet and Niklas’ hypothesis and ask whether angiosperm ‘trait flexibility’, i.e. the underlying (possibly genetic) ability to evolve intrinsic functional traits (e.g. fruits, flowers, leaves), repeatedly over time, space and taxonomic clades, may have allowed for evolutionary radiations and adaptation against the background of dynamic Cenozoic environmental change. If true, I would expect many more evolutionary transitions in functional traits during angiosperm evolution (e.g. from bird pollination to wind pollination) than in gymnosperms and pteridophytes. I published this idea and a first assessment using a meta-analysis approach as a Tansley insight in New Phytologist.
Onstein is ON 