Institute of Integrative Biology, ETH Zürich, Switzerland
Phylogenetic trees of present-day species allow inference of the rate of speciation and extinction which led to the present-day diversity. Classically, inference methods assume a constant rate of diversification, or neglect extinction. I will present a new methodology which allows speciation and extinction rates to change through time (environmental-dependent diversification) as well as with the number of species (density-dependent diversification). Particular attention is paid towards the specific species sampling schemes for incomplete phylogenies.
Using this new framework, I show that mammalian diversification rates are mainly determined by environmental effects; however, I reject the hypothesis of accelerated mammalian evolution following the extinction of dinosaurs at the KT-boundary. The other two considered datasets, birds and ants, reveal density-dependence as the main factor determining diversification rates. In contrast to previous results, the new analyses predict high extinction rates for birds, as well as no major environmental impact on diversification for ants.
The methods can easily be applied to other datasets using the R packages TreePar and TreeSim available on CRAN.