Costs and benefits of mate choice in the lek-breeding reed frog,Hyperolius marmoratus

Direct benefits to females of choosing mates have recently been suggested to play a role in the evolution of female preferences even in non-resource-based mating systems. Direct benefits affect the fecundity or survival of females whereas females gain indirectly from being choosy by passing on good genes to offspring or by producing sons that are themselves more attractive to females. I investigated two potential direct benefits that females gain from being choosy in the lek-breeding painted reed frog, Hyperolius marmoratus broadleyi: assurance of fertilization and reduction in search costs. Males did not differ in their fertilization rates, indicating that choosy females did not benefit by gaining higher rates of fertilization. However, costs of mate searching were high due to predation risk by brown water snakes, Lycodonomorphus rufulus, at the breeding site. Small natural choruses were monitored using an acoustic localization technique based on the measurement of arrival time differences of a male's signal at an array of microphones. Females preferred males that were near to their release site and that called at high rates. These preferences were corroborated experimentally in two-choice arena trials and are consistent with the notion that females should reduce search time under high predatory pressure. Because sampling costs are high, females are selected to reduce search time and males are predicted to call so that females can locate them easily. High sampling costs also make direct selection on female preferences a plausible solution to the lek paradox.