Do amphibians follow Bergmann's rule?

Abstract

It is not clear whether Bergmann's rule, larger size within species in cooler areas, holds for any group of ectotherms. Data are presented and used to test whether amphibians show body-size patterns that follow Bergmann's rule. Available data with respect to latitude and elevation suggest that amphibians in general follow Bergmann's rule, with 23 of 34 species showing a larger body size at higher latitudes or elevations and an overall grand mean correlation coefficient of +0.35 for size with latitude or elevation. Salamanders show body-size patterns consistent with the overall trend, with 13 of 18 species having a larger body size at higher latitudes or elevations and a grand mean correlation coefficient of +0.42 for size with latitude or elevation. Anurans show a weaker trend towards concordance with Bergmann's rule with respect to latitude and elevation (10 of 16 species), but the grand mean correlation coefficient is significantly positive (+0.31). The relationship between body size and environmental temperature is less clear. Overall, amphibians show weak concordance with Bergmann's rule (9 of 16 species). The results of the only two studies of salamanders are consistent with Bergmann's rule; however, data for anurans show no trend (7 of 14 species in accordance). Thus, while salamanders appear to follow Bergmann's rule, any trends in anurans are tentative.