A comparison of reproductive output of the Omei Treefrog (Rhacophorus omeimontis) between high and low elevations

Elevation that results in changes in climate, duration of breeding season and food resource has long been considered a major influence on the evolution of life-history traits in amphibians. The present study examined differences in reproductive output (clutch size and egg size) of the Omei Treefrog (Rhacophorus omeimontis) at two elevations (1000 m and 1700 m above sea level) in Baoxing County, western China. Within each population, female attributes (size and age) were responsible for much of the reproductive output variation in that larger or older females produced larger clutches of smaller eggs. Clutch size and egg size showed a significantly negative correlation, which was indicative of a trade-off between the two parameters. The high-elevation females were significantly larger than the low-elevation counterparts. After accounting for interpopulational difference in body size, clutch size, egg size and clutch volume differed significantly between the populations. For the high-elevation population relatively smaller clutches tended to be associated with larger eggs. Our findings suggest that females produce smaller clutches relative to body size and larger eggs in the high-elevation population to ensure that each egg is adequately provisioned in the face of cold climate and short duration of development.