Sexual Selection And Mating System Of Shinisaurus Crocodilurus And Their Effects On Offspring Fitness

Chinese crocodile lizard,Shinisaurus crocodilurus,is an endangered species.Research about their sexual selection and mating system might help us to protect them in wild and build a better breeding system.We conducted a serial of experiments in Guangxi crocodile lizard nature reserve.We divided males into different groups by their body size or color.We put two males and two females into an enclosure and record their behaviour using closed circuit television.Then we analyzed offspring paternity within clutches from these enclosures and a clutch from wild.We use body size,growth rates and mortality as indicators of offspring fitness to analyze the influence of crocodile lizards'mating system and sexual selection on offspring.Male color couldn't predict their dominance,while body size could.Larger males usually were the dominant ones.However,females didn't choose larger males nor males of certain color.Dominant males'encounter times with females and mating times were both higher than those of subordinate males,but their mating success rates didn't differ.Courtship behaviour and aggressive behaviour didn't differ between males of different color.Head bobbing mean frequency increased with male head size.Subordinate males court less and started in a nearer distance.Males didn't choose larger females or females of better body condition.Multiple mating didn't increase female clutch size or clutch weight.Moreover,mortality of multiple paternity(MP)offspring were higher than that of single paternity(SP)offspring.However,growth rates of MP offspring were higher than those of SP offspring,and they were lager before hibernation,but the differences were not significant.Offspring growth rates and their body size before hibernation were not correlated with neonate size,but smaller and lighter offspring had higher mortality.We also show that multiple paternity exists in wild as well.The results show that male color might be not under sexual selection,while body size and head size are.Females might prefer dominant males,but it could also be the result of dominant males excluding subordinate males.Subordinate males might be sneaker,but the enclosure might not be big enough for them to succeed.Female choice was a combination of preference to male morphological traits and courtship behaviour,and they might be in opposite direction.Multiple mating couldn't offer females direct offspring,but might offer them indirect benefits.Even though that MP offspring mortality was higher than SP offspring mortality,and they were smaller and lighter,but long-term growth rates of MP offspring might be higher than those of SP offspring.Besides,female could choose males with certain traits or avoid inbreeding through cryptic female choice when they couldn't make pre-copulatory mate choice.As for males,that the cost of mating was not high might be the reason why they didn't choose.Before we confirm any benefits females could gain from multiple mating,we should avoid putting a females with over one males into a same enclosure in breeding program.