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Luo Z.,Central China Normal University | Hu M.,Central China Normal University | Hong M.,Central China Normal University | Li C.,Central China Normal University | And 5 more authors.
Journal of Zoology | Year: 2015

Across taxa, females are routinely choosier than males in selecting mates. Several hypotheses have been advanced to explain genetic benefits behind female strategies. The inbreeding avoidance hypothesis suggests that females avoid mating with close relatives, thereby avoiding the matchup of deleterious recessive alleles. Outbreeding avoidance hypothesis suggests that females should not mate with too distantly related individuals so as to avoid the breakup of coadapted gene complexes. Although previous studies have suggested that selection should favor individuals that optimize the balance between inbreeding and outbreeding, detailed research is necessary to document the trade-off between them and variability in mate choice across a gradient of inbreeding levels among populations. The good genes and the genetic compatibility hypotheses predict that females choose mates according to costly traits and genetic dissimilarity, respectively. Thus, to document inbreeding or outbreeding depressions and assess the contributions of mate choice based upon good genes versus genetic compatibility, we examined egg production, collected body length measurements and genotyped five microsatellite markers in six populations of Asiatic toad (Bufo gargarizans). Our results revealed that the incidence of inbreeding was higher than that expected under the assumption of random mating and relatedness between mated individuals increased when the average inbreeding level increased among populations. Our findings did not support the good genes or the genetic compatibility hypotheses. Although some other processes could have influences on mate choice of Asiatic toad and need to be tested, our results indicated that, in small and isolated toad populations, the limited availability and high cost of obtaining unrelated mates may promote outbreeding avoidance and adaptation to inbreeding to be the critical drives of female mate choice. © 2014 The Zoological Society of London.

Luo Z.,Central China Normal University | Li C.,Central China Normal University | Wang H.,Central China Normal University | Shen H.,Central China Normal University | And 5 more authors.
Behavioral Ecology and Sociobiology | Year: 2016

Abstract: Male-male competition and female mate choice based on ornamentation and genetic traits are the main drivers of animal sexual selection and group spawning. If male-male competition is intense, males with specific phenotypes should have advantages in breeding success or occupying superior mating positions. If female choice is important, females should have preferences for mate relatedness or males with good genes or optimal genetic compatibility against themselves. To detect the intensities of male-male competition and female choice and test the good genes and genetic compatibility hypotheses, we observed breeding behaviors, measured individual body lengths and breeding success indicators, and calculated male genetic heterozygosity, male–female relatedness, and genetic dissimilarity in an Omei treefrog (Rhacophorus omeimontis) population in Badagongshan, China. Our analyses showed that larger males obtained larger mates, had more mating opportunities, occupied better amplectant positions, and produced more offspring. However, females showed no inbreeding/outbreeding bias in mate choice, and the good genes and genetic compatibility hypotheses were not supported in female selection on mates and amplectant positions. We considered male-male competition as the main driver of sexual selection and group spawning in this prolonged mating species because the cost of choosing mates with specific genetic traits may be high for females. Significance statement: Male-male competition and female mate choice are the main drivers of animal sexual selection and mating behaviors. However, their impacts on the evolution of mating system are not yet quite clear. By studying the Omei treefrog, a Chinese endemic anuran species with common group spawning behaviors, this research posed the importance of male-male competition and female mate choice and discussed the mechanisms of sexual selection and multiple mating, which are the most essential and debated issues in evolutionary biology and behavioral ecology. We found that, in this prolonged mating and lek-patterned species, male-male competition is the main driver of sexual selection and group spawning. Larger males can get larger females, have more breeding opportunities, occupy better amplectant positions, and thus, obtain greater numbers of offspring. Whereas, females have no significant preferences on ornamentation and genetic traits of their males or mating positions, and the inferior males “make the best of a bad lot” by joining mating pairs to produce mating groups. Our study provides empirical evidence of reproductive mechanisms of amphibian species and could advance the understandings on the evolution of animals’ sexual selection and mating system. © 2016, Springer-Verlag Berlin Heidelberg.

Zhao M.,Central China Normal University | Li C.,Central China Normal University | Zhang W.,Central China Normal University | Wang H.,Central China Normal University | And 5 more authors.
Animal Behaviour | Year: 2016

Female polyandry and corresponding multiple paternity have been detected in many species. Several hypotheses, such as the fertility guarantee hypothesis, the good gene hypothesis, the genetic compatibility hypothesis and the genetic diversity hypothesis, have been proposed to explain the evolution of female polyandry. Anuran amphibians are widely observed to breed in polyandrous spawning groups; however, few studies have evaluated multiple paternity in these species or the evolutionary mechanisms underlying polyandry. In this study, we addressed these questions pertaining to polyandry in the Omei treefrog, Rhacophorus omeimontis. Eight microsatellite markers of R. omeimontis were used to determine the patterns of paternity. Paternity analyses revealed that offspring were multiply sired in a majority (79.07%) of the polyandrous spawning groups. A male's reproductive output during a breeding season was greatly affected by the mating rate, revealing that male fitness benefited from multiple copulations. By contrast, no evidence supported the fertility guarantee hypothesis that polyandry increases the fertility rate of females or the compatible/good gene hypotheses that polyandrous females produce more compatible or superior offspring. The increased allelic diversity observed in polyandrous clutches is probably a nonadaptive by-product of multiple mating. In conclusion, males join as many copulations as possible to increase their reproductive success, regardless of whether their mate has already been in amplexus with other males. Females may gain no benefits from polyandry but are incapable of preventing superfluous males from joining the mating group due to the physical characteristics and breeding behaviour of anurans. Thus, in R. omeimontis, male pursuit of higher reproductive success is the primary explanation for female polyandry. © 2015 The Association for the Study of Animal Behaviour.

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