PI: Michael Strand, Institution: University of Georgia Research Foundation Inc.
Social animals are characterized by the development of castes in which some colony members reproduce while others function as altruistic helpers. Most social species are insects like ants, bees, and termites. Caste systems have also evolved in selected groups of aphids, thrips, and polyembryonic wasps. The conditional switch controlling caste formation usually involves environmental stimuli that act upon processes that regulate development of individuals. Unlike other social species, embryos of polyembryonic wasps develop clonally to produce large numbers of genetically identical offspring and two morphologically distinct castes. All embryos in a clone exist in an identical environment, the host, yet develop into either reproductive larvae that mature into adult wasps or soldier larvae whose function is defense. Previously conducted background studies indicate that caste determination in the polyembryonic wasp Copidosoma floridanum involves the inheritance of germ cells. Embryos that inherit germ cells form reproductive larvae, whereas embryos that do not form soldiers. The objective of this research is to understand how the presence or absence of germ cells causes individuals with the same genes to develop so differently. Molecular methods will be combined with experimental studies to determine how germ cells are asymmetrically distributed among embryos and how the presence of germ cells affects expression of other genes. The results of this study will improve understanding of how caste formation is regulated, the function of germ cells in development, and the evolution of altruism in multicellular organisms.
