Department of Biosciences, Simon Fraser University, Burnaby, BC, V5A 1S6, 778-782-3540. http://www.sfu.ca/~tsa19
Understanding how a single genome can produce a variety of different phenotypes is of fundamental importance in genetics and developmental biology. One of the most striking examples of phenotypic plasticity is the female caste system found in ants and other eusocial insects, where different phenotypes are associated with reproduction (queen caste) or helping behaviour (worker castes). A long-standing paradigm for caste determination was that female eggs are always totipotent with the important morphological and physiological differences between queens and workers stemming solely from a developmental switch during the larval stage under the control of nutritional and other environmental factors. However, there are an increasing number of examples showing genetic components to caste determination as well as maternal effects influencing the developmental fate of females. I will present a broad overview of the studies providing strong direct and indirect evidence for a genetic component to caste differentiation and discuss factors that may have led to the evolution of genetically hardwired caste systems. In addition, I will argue that a purely environment- controlled caste system is very difficult to demonstrate and probably unlikely to occur in genetically heterogeneous societies. Detailed molecular analyses and breeding experiments are likely to uncover additional cases of genetically-determined queen and worker determination and various degrees of genetic predisposition towards a particular caste.