Ecology, sexual selection and adaptive female preferences

The role of ecology in the evolution of mating systems remains a central, yet inadequately understood question in behavioral ecology. In particular, the relative importance of direct and indirect benefits to mate-choice remains enigmatic despite decades of attention. To understand the importance of territory quality and male attributes in mating systems, I experimentally uncoupled the association between large male body size and high quality territories. I removed rock habitat from the territories of large males, and deposited it on the adjacent territories of their smaller male neighbors. Adding rock to a male's territory improved the thermal properties of the territory by increasing the range of micro-climates available for thermoregulation. Improved territories also had increased structural heterogeneity compared to reduced quality territories. Consequently, juvenile growth rates and survival were both significantly higher on improved territories. Adult survival was significantly lower on high quality sites and this was likely due to increased depredation by snakes. Nevertheless, the direct thermal and reproductive benefits of residing on high quality territories led males to compete vigorously over improved territories. Males exhibited two alternative strategies for territoriality. The two strategies, usurp and defend, had unequal arithmetic mean fitness and I demonstrate that variance in usurper fitness maintains the two strategies despite unequal fitness. Females demonstrated a strong preference for improved territories and experienced direct benefits of increased egg mass compared to females on low quality territories. Females also preferred to mate with large males even though large males did not control the best territories after my experimental manipulations. Furthermore, female preference for large male body size was also adaptive. Progeny sired by large males were larger and in better condition than progeny sired by smaller males. Moreover, females were more likely to produce sons with eggs sired by large males, and daughters with eggs sired by smaller males. I discuss the role of territory quality in driving the evolution of mating systems. Specifically, I consider the evolution of male-male competition and female choice for direct and indirect benefits.