Comparative Social Biology of Sponge-Dwelling Snapping Shrimp (Synalpheus)

College Of William & Mary Virginia Institute Of Marine Science, Gloucester Point VA

Investigators

Abstract

COMPARATIVE SOCIOBIOLOGY OF SPONGE-DWELLING SNAPPING SHRIMPS J. Emmett Duffy School of Marine Science The College of William and Mary Eusociality, characterized by cooperative colonies in which most members sacrifice individual reproduction, has long presented a fundamental paradox for behavioral and evolutionary ecology. According to Hamilton's rule, social behaviors can be understood as solutions to challenges imposed by the environment mediated through the genetic relatedness of interactants. A full understanding of social evolution thus entails an accounting of the genetic relationships among group members, the basic ecological constraints on populations, and some means of assessing the evolutionary consequences of their interplay. This proposal employs complementary genetic, behavioral, and comparative approaches to assess the interplay between kin structure and social biology, and some of its macroevolutionary consequences, in fostering social evolution in the species-rich and socially diverse sponge-dwelling shrimps (Synalpheus), one of the rare animal groups in which eusociality has arisen repeatedly among closely related species. The project has two principal objectives: (1) Assess the influence of breeding system, and consequent genetic structure of colonies, on behavioral dynamics and the maintenance of extreme reproductive skew in two independently evolved, and demographically divergent, eusocial shrimp species Synalpheus regalis and S. chacei. This will be accomplished by genotyping individuals from field-collected colonies of each species at eight microsatellite loci, and experimentally assessing levels of conflict and cooperation among individuals in captive colonies in the laboratory. This research will characterize the distributions of relatedness, aggressive dominance, mating success, and parentage among individuals within colonies, and of relatedness within vs. among colonies. (2) The longer-term evolutionary consequences of these social dynamics will be approached in a comparative framework by exploiting the social diversity among species of Synalpheus, building on the recently completed phylogenetic reconstruction of the sponge-dwelling clade. Phylogenetically independent contrasts will test the association, predicted by theory and empirical studies of social insects, among colony size, reproductive skew, and caste differentiation. This research will provide a new window on the origin, adaptive significance, and macroevolutionary consequences of eusociality in a unique, socially diverse clade of non-insect invertebrates, and will contribute to evaluating the generality at a broad taxonomic level of theories for the evolution of advanced animal societies based primarily on data from social insects.