Abstract: Sexual size dimorphism is the phenomenon that conspecific males and females show different magnitudes or directions of body size variations at broad geographic and phylogenetic scales. The Rensch’s rule describes the patterns of sexual size dimorphism allometry, in that body sizes of males are larger than females in large-sized species and body sizes of females are larger than males in small-sized species. Sexual selection, fecundity selection, and sex-specific phenotypic plasticity hypothesis have been proposed to explain the Rensch’s rule or the inverse pattern. Amphibians and reptiles are widespread except Antarctica. They have abundant phenotypic traits, and exhibit a wide sexual size dimorphism, from marked male bias to strong female bias, which are excellent model organisms to test Rensch’s rule. We reviewed the research progress on Rensch’s rule in amphibians and reptiles, with the focus on the definitions, statistics, patterns, and mechanisms of this rule. We further proposed future research direction of Rensch’s rule.

Key words: body size, sexual size dimorphism, allometry, Bergmann’s rule, Island’s rule