Amat, F.

Patterns and allometries of sexual size dimorphism in salamanders and the rejection of Rensch’s Rule. pp. 145-150 plus Supplementary data.

Abstract. Sexual size dimorphism (SSD) is a result of selective pressures acting differently on size in each sex. SSD is examined in salamanders by analysing data from 356 species representative of all major lineages to identify which sex is more frequently larger and test the validity of the Rensch’s Rule. Most species of salamanders exhibit a female-biased SSD (66.9% of species analysed). The overall mean SSD index was 0.061, indicating that sex-linked differences in SVL were not large. Standard major axis regression using species data and phylogenetically independent contrasts indicated a general lack of fit of Rensch’s Rule to the allometric patterns found for the whole data set and the analysis restricted to major families. Fecundity selection is more influential on female SSD than sexual selection associated with inter-male competition for mating partners. However, this selective pressure could be less forceful in females to produce a departure from isometry of biometric relationships between sex-linked sizes, thus leading to the rejection of Rensch’s Rule.

Key words. Amphibia, Urodela, morphology, size, sexual dimorphism, Rensch’s Rule.