Similarities and differences in adult tortoises: a morphological approach and its implication for reproduction and mobility between species

Abstract

Sexes in Chelonia display marked differences. Sexual size dimorphism (SSD) is important in evolutionary biology. Different sexual strategies result in species specific selection. Biometric variation in male and female tortoises of two species is studied. Eighteen biometrics were measured in 75 museum specimens (20 Testudo graeca; 55 T. hermanni). Nine of 18 parameters in T. hermanni and two of 18 in T. graeca were sexually dimorphic. Multivariate analyses (principal component analysis) highlighted two components, with bridge length the first and anal divergence the second component. The bridge length can be used to separate sexes and species. Males of both species were most different, whereas females of two species overlapped in body shape measurements. We hypothesise that female similarity could be a by-product of reproductive biology and sexual selection that optimise individual fitness.