Variation in mating patterns in the Andrew's toad Bufo andrewsi along an elevational gradient in southwestern China

Abstract

The mating pattern in animals is regarded as a consequence of sexual selection of phenotypic characters, and variations in sexual selection strength will result in different mating patterns. In view of this, we studied variation in mating patterns in the Andrew's toad Bufo andrewsi across five elevation populations (range = 1000–2100 m) in southwestern China. The results showed that there was a high male-biased operational sex ratio in all populations. Mean adult male SVL differed significantly among localities and amplexus conditions, showing a significant among-locality difference in large male advantage. Mean age of adult males differed among localities and mating status, suggesting an old-male mating advantage for all populations. A significant age-assortative mating pattern was only observed in the 2100-m site. There were significant among-locality differences in large or old-male advantage and size or old-assortative patterns. Among the sites, the operational sex ratios were positively correlated with size ratios of males (amplectant SVL/non-amplectant SVL), but not age ratios of males (amplectant age/non-amplectant age). The strength of size-assortative mating did not increase with increasing operational sex ratios.