Inferring the Past for Traits that Alter Speciation and Extinction


I will describe a likelihood-based approach (BiSSE) that uses information from the relationships among species (a phylogeny) to infer how traits evolve and influence speciation and extinction rates. The shape of the phylogeny of a group of species contains information about past evolutionary changes: higher speciation rates, for example, give rise to shorter branch lengths. The likelihood method that we have developed uses the information contained in a phylogeny and integrates over all possible evolutionary histories to infer the speciation and extinction rates for species with different character states. Our method can be used to provide more detailed information than previous methods, allowing us to disentangle whether a particular character state is rare because species in that state are prone to extinction, are unlikely to speciate, or tend to move out of that state faster than they move in.

UBC Robson Square

Speaker Bio

Sarah (Sally) P. Otto. University Killam & CRC (Tier 1) Professor, Department of Zoology & Director, Liber Ero Post-doctoral Program, University of British Columbia; B.Sc. and Ph.D. from Stanford University. Understanding how evolution has led to the remarkable diversity of life is the key motivating force behind my research. Mathematical models allow us to determine which evolutionary transitions are plausible, which are probable, and which are inaccessible. Complementing this theoretical approach, we use experimental evolution to track yeast as they evolve, allowing us to test alternative hypotheses. Dr. Otto’s research into the evolutionary forces leading to biological diversity has resulted in over 170 publications and a book. Awards include a MacArthur Fellowship, a Guggenheim Fellowship, the Steacie Prize (National Research Council, Canada), and fellowship in the Royal Society of Canada, the American Academy of Arts and Sciences, and the National Academy of Sciences.