Sexual dimorphism in fire-bellied toads Bombina spp. from the central Balkans

Abstract

The direction and level of sexual size dimorphism (SSD) was examined in fire-bellied toads from the central Balkans. Samples were taken from 12 populations: three Bombina bombina, three B. variegata variegata and six B. variegata scabra populations. Intersexual variation of 20 morphometric characters was analysed. In addition, correspondence analysis of eight qualitative characters was performed. The results showed that, though body length had an inconsistent pattern of intersexual variation across taxa, other traits contributed to statistically significant level of SSD. The analysis on multivariate level revealed a highly significant effect of population in all three taxa, and significant effect of sex on character variation. Discriminant analysis confirmed a higher level of intersexual differences in B. variegata compared to B. bombina. Correspondence analysis showed that females and males were similar with respect to qualitative traits in all three taxa. At the univariate level, the most prominent features were: significant differences in tibia length in all three taxa, and highly significant differences in head width in B. bombina and in humerus length in B. v. scabra. These results are discussed with respect to specific reproductive behaviour and possible ecological differences between sexes.