The Influence Of Body Size And Sex Ratio On Reproductive Success In Rhacophorus Omeimontis

Sexual selection is quite crucial to breeding and evolution of animals. It leads to the evolution of traits related to fitness. Many studies have shown that these traits are not only associated with mating success, but also closely related to the reproductive success. Furthermore, the influence of male-male competition and female choice based on body size on reproductive success has also been reported widely. And in most animals, individuals with lager body size can benefit more from the competition and enhance the chance of mating. Especially in amphibians, dominant individuals tend to be the lager or older ones.It's a great significance for studying the factors affecting reproductive success of animals, by which we can understand the reproductive behavior and reproductive strategies of species. For Rhacophorus omeimontis, current studies are limited to mating behavior, spawning, spawning sites, foam-nest features, the influence of body size and individual age on mating success, and the factors affecting the reproductive success have not yet been explained. Also in previous studies, the reproductive success tends to be represented by the number of males which can approach to females. But strictly speaking, this method is inadequate because an individual may get reproductive success only if they have survived offspring. In order to solve the uncertain problems above, we need to import genetic molecular markers.In our studies, we have used microsatellite makers to identify paternity in the Omei tree frog, and analyzed the impact of body size and sexual ratio on reproductive success. About 154 individuals (29 females; 125males) of body size,29 clutches in clutch size, sexual ratio and fertilization rate were collected from breeding site. We found that, almost 84.6% of clutches were multi-paternity from paternity analysis in nine microsatellite loci. The clutching sex ratio was one to eight and not all males had offspring.There were no significant correlations between females'body size and clutch size or fertilization rate, male body size and the proportion of offspring, and the same with the clutching sex ratio and the proportion of offspring. However, a significant correlation was found between sexual ratio and fertilization rate (P<0.05). In all clutches, there was an obvious reproductive skew in males, and it decreased extremely significantly with clutching sex ratio increasing (P<0.001).Along with the increase in the number of mating males, the number of males gaining fitness enhanced and the male-biased reproductive skew decreased. Correspondingly, fertilization rate increased with the increase in clutching sex ratio. These results explained clearly the polyandry in R. omeimontis, which bring higher fitness for them. Such potential benefit is likely to be one reason of high levels of multi-paternity in R. Omeimontis.