Phylogenetic analyses of mode of larval development

Phylogenies based on morphological or molecular characters have been used t o provide an evolutionary context for analysis of larval evolution. Studies of gastropods, bivalves, tunicates, sea stars, sea urchins, and polychaete s have revealed massive parallel evolution of similar larval forms. Some of these studies were designed to test, and have rejected, the species select ion hypothesis for evolutionary trends in the frequency of derived larvae o r life history traits. However; the lack of well supported models of larval character evolution leave some doubt about the quality of inferences of la rval evolution from phylogenies of living taxa. Better models based on maxi mum likelihood methods and known prior probabilities of larval character st ate changes will improve our understanding of the history of larval evoluti on.