Meeting Abstract

P3.54  Friday, Jan. 6  Geographic range size and diversification in tailed and tailless molgulid ascidians MALISKA, M.E.*; SWALLA, B.J.; Department of Biology, University of Washington; Department of Biology, University of Washington mem24@uw.edu

A long standing interest in marine invertebrate evolution has been over larval development’s contribution to dispersal and speciation. Newly developed methods to assess how geographic range size can affect diversification rates on molecular phylogenies has opened up new avenues of research on this topic. Ascidian species (Tunicata: Ascidiacea) in the Molgulidae are found to have urodele, tailed, chordate larvae with notochord and muscle as well as closely related species with anural, tailless larvae that completely lack larval structures, including the sensory otolith and muscle and notochord in the tail. Tail loss in the Molgulidae has occurred multiple times evolutionarily. We show that tailless species have smaller geographic sizes than tailed species, and hypothesize that species with tailless larvae have a higher diversification rate. With data collected from at least four independent lineages of tailless larvae, we assessed if the evolution of tail loss in these species has affected diversification rates using binary character speciation and extinction models. We also evaluate the impact of geographic range size on diversification rate using a quantitative speciation and extinction model.