PhD defence Ryan Brewer
Ryan Brewer (TRÊS)
Promotores: Prof. R.S. Etienne, Prof. F. Lens (LU), Prof. L.M. Lima Valente (TRÊS/Naturalis)
Trait-dependent diversification and biogeography of Canary Islands angiosperms
In this research, I use phylogenomics, morphological and environmental trait data, and biogeographical modelling to examine how the flowering plant (angiosperm) community of the Canary Islands is distributed in time, space, and across their phylogeny. To do so, I generated the most complete time-calibrated phylogenomic dataset of any archipelago flora to date using 353 nuclear genes and 166 fossil calibrations, covering ~60% of the non-monocot flora (Chapter 2). Using a dynamic, stochastic island biogeography model, I found strong evidence of trait-dependent diversification: perennial and insular woody lineages show faster speciation and lower extinction and colonisation rates than annual or non-woody lineages. Interestingly, there was no relationship between clade age and diversity.
I then applied this phylogenetic framework to identify environmental correlates of five plant growth forms, revealing that niche space is largely overlapping but delineated by temperature/precipitation seasonality and terrain rugosity, with insular woodiness potentially an adaptation to mild climatic seasonality and rugosity. Additionally, I combined this phylogenetic framework with morphological trait data to test a novel trait-dependent diversification model specifically tailored to islands, TRAISIE (TRait-dependent Assembly of Island biota through Speciation, Immigration, and Extinction). First, we applied TRAISIE to simulated data to find the dataset conditions required for accurate evolutionary rate estimation. Then we applied TRAISIE to the Canary Islands dataset and found faster diversification rates in woody and perennial lineages. Together, these findings provide the first empirical support for insular woodiness promoting diversification at the community level, link plant distributions to rugosity, and help develop a general trait-dependent diversification model for islands.