The evolution of territoriality explored in polymorphic Mnais damselflies

Damselflies (Odonata: Zygoptera) are a fruitful model system for the study of territoriality, and the evolution of morphology and behavior. The species Mnais costalis and M. pruinosa are one such system: these two species, found in Japan, have polymorphic males, with a colorful ‘territorial’ form and a clear-winged ‘sneaker’ form. Both species show similar polymorphisms in allopatry, but when sympatric the polymorphism is sometimes lost, with M. costalis becoming completely colorful, and M. pruinosa becoming clear-winged. Despite this loss of color polymorphism, territorial and sneaker forms persist in both species. Through a combination of theoretical modeling and behavioral choice experiments in the field, we are exploring the dynamics of this system. Our theoretical results suggest that the influence of female choice, previously unexplored in models of territoriality, is an important component in the evolution and maintenance of territorial behavior in males. In exploring the differences between polymorphic and monomorphic sympatric populations, we found that orange-wing M. costalis males showed higher aggression to other orange-winged M. costalis males in comparison to clear-winged M. pruinosa males in some monomorphic populations when compared to polymorphic populations, but further tests are ongoing. We will explore the implications of these data for the evolution and maintenance of both territoriality and polymorphism, and what these results can tell us more generally about territorial organisms. We are also exploring the population genomics of these species, to investigate the evolutionary histories of polymorphic and monomorphic sympatric populations.