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Adaptations can endow species with complex traits that enable them to occupy new niches. To adapt to the arboreal lifestyle, treefrogs have evolved a suite of complex traits for climbing and gliding; to date, however, the molecular mechanisms underpinning these adaptations are unknown. Here, based on two de novo-assembled Asian treefrog genomes, genes related to limb development showed evidence of accelerated evolution. Furthermore, the PPL gene that regulates the keratin cytoskeleton showed conservative substitution within the genus Rhacophorus. These genetic changes contribute to limb and toe-pad morphogenesis, providing fundamental adaptations for climbing and grasping. Behavioral and morphological comparisons clarified the gliding function of interdigital webbing and the different developmental patterns between fully and weakly webbed feet. Time-ordered gene coexpression network analysis of gliding Rhacophorus kio and nongliding Rhacophorus dugritei tadpoles revealed specific coexpression patterns for fully webbed feet, which involved the Wnt signaling and vascular remodeling pathways. These findings highlight the molecular basis of phenotypes that facilitate expansion into new niches and provide insights into the importance of local adaptation in shaping phenotypes and locomotion patterns. [ABSTRACT FROM AUTHOR]

The compensation hypothesis predicts that one testis may grow more for compensating for a reduced function in the other testis, thus exhibiting a directional asymmetry in testis size. In this study, we tested the prediction of the compensation hypothesis in the Chinese endemic Tree Frog Hyla gongshanensis jingdongensis in a population in Kegong Reserve site of Yunan Province in western China. For fifty-three male samplings, we found that the left testis size was significantly bigger than the right testis, which exhibited a significantly directional testis asymmetry, consistent with the evidence that mainly the left testis is functional with the right testis having a compensatory role, i.e. the left testis would increase in size if the right testis became non-functional. However, the relative testes size and the degree of testes asymmetry were not correlated with body condition in this species, suggesting that the testes asymmetry can not reflect male quality: high-quality individuals would not have more asymmetric testes. [ABSTRACT FROM AUTHOR]

The study of life-history traits in organisms mainly focuses on the female reproductive investment mode and its influencing factors. Offspring number and size as two plastic life-history traits, are commonly used to determine the reproductive investment. In this study, we evaluated the evolutionary trade-off between clutch size and egg size in the spot-legged treefrog (Polypedates megacephalus) along an altitudinal gradient. The results showed that females did not exhibit a significant correlation between body size, clutch size and egg size within each population, apart from the Leigong population. We did not find any evidence for the trade-off between clutch size and egg size within or among populations; however, clutch size and egg size from the highest-altitude population were larger than those from the lowest-altitude populations. Our findings suggest that the larger egg size may compensate for the increased mortality rates of their offspring at high altitudes. [ABSTRACT FROM AUTHOR]

Phenotypic flexibility of morphological characters is widespread in the animal kingdom. In the present paper, we investigated altitudinal variation in organ size (heart, lungs, livers, kidneys and digestive tract) in the spotlegged treefrog (Polypedates megacephalus) across three populations along an altitudinal gradient in southwestern China. Both heart and lung mass increased with altitude, and is possibly linked to a lower oxygen supply at high elevations; a higher liver mass suggested the increased need for energy stores. Despite significant differences between populations, we found no distinct cline in the length of the digestive tract according to altitude. [ABSTRACT FROM AUTHOR]

Variation in temperature and breeding season length caused by altitude has long been considered a major influence on the evolution of life-history traits in amphibians. Here, we examined differences in reproductive investment (testes mass and sperm length) of male spot-legged treefrog (Polypedates megacephalus) from two altitudes (680 m and 1300 m above sea level) in Guizhou Province, western China. Relative testes size from the high-altitude population was larger than that of the low-altitude population, whereas sperm length exhibited a converse cline. Testes mass but not sperm length increased with body size at both altitudes. Our findings suggest that differences in reproductive traits between populations might result from differences in the level of sperm competition. [ABSTRACT FROM AUTHOR]

Sexual size dimorphism (SSD) is a widespread phenomenon commonly attributed to sex-specific patterns of selection on body size. Using data from Dengchigou population of the Omei treefrog (Rhacophorus omeimontis) in Fengtongzhai National Nature Reserve, southwestern China, we evaluated the hypothesis that direct phenotypic selection on both males and females can produce SSD. Female biased-SSD was generally driven by selection on females due to fecundity advantage of large body size rather than sexual selection favouring large male body size. Furthermore, differences in life-history traits (i.e. growth rate and/or time available for growth) between the sexes also resulted in female biased-SSD. Our findings suggest that the relationship between female size and fecundity supports the prediction that selection for fecundity drives female biased-SSD. [ABSTRACT FROM AUTHOR]

The article presents a study using the predictions of the sperm competition theory to see if these can be applied to the polyandrous Omei treefrog (Rhacophorus omeimontis). The theory predicts that subordinate males may experience a higher intensity of sperm competition than dominant males resulting, in larger testes, larger sperm and greater longevity. Findings showed that small males do not invest more in sperm than large males and that they do not have larger sperms or greater longevity.