Meeting Abstract
Intensity of sexual selection is shaped by the operational sex ratio (OSR), which is the relative ratio of males to females ready to mate. At a proximate level, male biased OSR increases inter-male competition and variation in reproductive success. Spatial memory is a crucial mechanism for mating success, as individuals must locate potential mates in space and time. Intensity of sexual selection (at the population level) is potentially an important factor in shaping spatial memory, particularly in a mating context. Therefore manipulating the OSR context should reveal the importance of spatial memory in a population. For example, if male-male competition is high, males may benefit by knowing who and where their competitors are. Hence intra-sexual selection should influence spatial memory. We predict that individual variation in mechanisms controlling reproductive decisions and spatial memory may predispose some animals to thrive in one OSR context over another. We compare differences in reproductive success and performance in a spatial memory test for male prairie voles (Microtus ochrogaster) freely living in outdoor enclosures under male- and female-biased OSRs. Males in the male biased (MB) context performed better at the spatial memory test than those from the female biased (FB) context. We found that within each OSR context, reproductive success and spatial memory performance appear to be correlated. Neural phenotype for oxytocin receptors (a mechanism that modulates spatial memory and mating) tended to differ between contexts. Our results indicate that mechanisms associated with spatial memory are susceptible to selective pressures resulting from changes in OSR and could have immediate consequences on reproductive success.
