The making of a social insect – the regulatory architectures of social design

Gro V. Amdam, School of Life Sciences, Arizona State University, Tempe AZ 85287, USA; & Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, Aas N-1432 Norway; Gro.Amdam@asu.edu

Abstract: Evolutionary transitions from solitary to social living are studied at multiple levels of analysis ranging from molecular genetics and genomics to theories of inclusive fitness and altruism. The fundamental focus of this research is to explain how complex social phenotypes can evolve from ancestral solitary forms. In the mid 1980-ies, a theoretical framework addressing the proximate basis of social evolution was developed based on the biology of ants, wasps and bees. It proposed that the ovarian cycle, as a sequence of co-regulated physiological and behavioral events, provided a mechanistic basis for social evolution. The first evidence for this idea emerged from our studies of the honey bee (Apis mellifera) gene vitellogenin (Amdam et al. 2003; Amdam et al. 2004). The vitellogenin protein is a conserved egg-yolk precursor that can provide an explanatory bridge between the social behavior of bees and the ovarian cycle of an ancestral solitary form (Amdam et al. 2006). Functional studies show that vitellogenin gene activity act pleiotropically to affect sensory responsiveness, social foraging behavior and aging (Seehuus et al. 2006; Nelson et al. 2007). These and other recent results from our group (Hunt and Amdam 2005; Hunt et al. 2007; Patel et al. 2007) demonstrate how solitary life-histories provide the building-blocks from which complex social phenotypes can be assembled.

References
Amdam, G. V., K. Norberg, A. Hagen, and S. W. Omholt. 2003. Social exploitation of vitellogenin.
            Proc. Natl. Acad. Sci. USA 100:1799-1802.

Amdam, G. V., K. Norberg, M. K. Fondrk, and R. E. Page. 2004. Reproductive ground plan may mediate colony-level selection effects on individual foraging behavior in honey bees. Proc. Natl. Acad. Sci. USA 101:11350-11355.

Amdam, G. V., A. Csondes, M. K. Fondrk, and R. E. Page. 2006. Complex social behavior derived from maternal reproductive traits. Nature 439:76-78.

Hunt, J. H., and G. V. Amdam. 2005. Bivoltinism as an Antecedent to Eusociality in the Paper Wasp Genus Polistes. Science 308:264-267.

Hunt, J. H., B. J. Kensinger, J. A. Kossuth, M. T. Henshaw, K. Norberg, F. Wolschin, and G. V. Amdam. 2007. A diapause pathway underlies the gyne phenotype in Polistes wasps, revealing an evolutionary route to caste-containing insect societies. Proc. Natl. Acad. Sci. USA 104:14020-14025.

Nelson, C. M., K. Ihle, G. V. Amdam, M. K. Fondrk, and R. E. Page. 2007. The gene vitellogenin has multiple coordinating effects on social organization. PLoS Biology 5:673-677.

Patel, A., M. K. Fondrk, O. Kaftanoglu, C. Emore, G. Hunt, and G. V. Amdam. 2007. The making of a queen: TOR pathway governs diphenic caste development. PLoS ONE 6:e509.

Seehuus, S. C., K. Norberg, U. Gimsa, T. Krekling, and G. V. Amdam. 2006. Reproductive protein protects sterile honey bee workers from oxidative stress. Proc. Natl. Acad. Sci. USA 103:962-967.