Meeting Abstract
Marine crustaceans are spectacularly diverse, both taxonomically and ecologically. Many lineages of crustaceans have formed interspecific symbiotic relationships with a variety of marine organisms, including corals, fish, echinoderms, sponges, tunicates, and even other crustaceans. These symbioses include a wide array of interactions, from the cohabitation of burrows, to specialized fish cleaning behavior, to living inside the canals of sponges or the mantle cavities of bivalves. The evolution of these symbiotic interactions can potentially have significant effects on diversification rates. Here we investigate two mutually exclusive hypotheses. The first, the “dead-end hypothesis,” suggests that symbiotic crustaceans are limited by their interaction with their host and therefore cannot diversify into new geographic or ecological spaces, i.e. symbiotic lifestyles represent an “evolutionary dead-end.” The second, the “adaptive radiation hypothesis,” suggests that the evolution of symbiotic lifestyles facilitates rapid radiation through the colonization of new host taxa. The former hypothesis predicts a reduced diversification rate in symbiotic lineages compared to their free-living relatives, whereas the latter predicts the opposite scenario. To test these hypotheses, we utilize published molecular phylogenies of eight groups of marine crustaceans, including snapping shrimp, pea crabs, and amphipods, among others, as case studies. We use multiple speciation and extinction (SE) models to compare diversification of symbiotic and free-living lineages in each case study and compare the results of different case studies and model types.
