Costs and benefits of polyandrous mating to the female emerald treefrog (Zhangixalus prasinatus), a lek-chorusing anuran

Abstract: Polyandrous mating, where females mate with multiple males, can be caused by male manipulation, primarily benefiting males. Females, conversely, may suffer costs without direct benefits. According to the good gene hypothesis, females should choose superior males to pass on good genes to their offspring in lek-breeding species. However, when females are compelled to mate against their preference, which leads to polyandrous mating, indirect genetic costs arise, with lower-quality males fathering some offspring. Despite these costs, polyandrous mating may potentially benefit females through fertilization insurance and increased genetic diversity. This study investigated the costs and benefits of polyandrous mating in the lek-chorusing treefrog (Zhangixalus prasinatus) by comparing clutch fertilization success, offspring performance (embryo viability, survival, growth, development) linked to fitness, and allelic diversity between the clutches after monandrous and polyandrous mating. Our results showed that polyandrous mating (1) did not increase fertilization success, (2) did not affect embryo viability, offspring survival, growth, or development, but (3) increased genetic diversity. Additionally, we found that primary males (chosen by females) sired more offspring than peripheral males (not chosen by females). The small proportion of the clutch sired by peripheral males suggests that polyandrous mating in Z. prasinatus may be driven by males to pursue reproductive success, and may, as a by-product, potentially benefit females by increasing their offspring's genetic diversity. Therefore, peripheral males achieve higher reproductive success, while females lack apparent costs, which is suggested to be a likely reason for the moderate frequency of polyandrous mating in this species. Significance statement: Our study investigates the impact of polyandrous mating on female emerald treefrogs (Zhangixalus prasinatus). Our findings reveal that while polyandrous mating neither enhances nor reduces fertilization success, embryo viability, offspring survival, growth, or development, it does increase genetic diversity within clutches. Although this genetic diversity may be a by-product of male reproductive strategies, it potentially offers females indirect genetic benefits, which may help explain the moderate frequency of polyandrous mating in this species. Our research contributes to a deeper understanding of mating systems and reproductive strategies in lek-breeding anurans.