Sexual body size and body shape dimorphism of Testudo hermanni in central and eastern Serbia

Abstract

Hermann’s tortoise (Testudo hermanni) is widely distributed in western and southern Europe. Most populations in the western part of the distribution range (e.g. Spain, France, Italy) are severely reduced, and relatively well studied, whilst the species is still abundant in eastern areas (i.e. the Balkans). However, essential biological information (e.g. main morphological, ecological, and behavioural characteristics) for the Balkans are still extremely limited. As reptiles exhibit strong geographic variation in most morphological, as well as life history traits, gathering data from distant areas is important. We present data from two populations of T. hermanni in Serbia, focusing on sexual dimorphism in body size and body shape. We found that almost all of the 43 morphological traits analysed were significantly different between sexes and that sexual size and sexual shape dimorphisms were not expressed in similar ways. Notably, sexual size dimorphism (SSD) was more pronounced than sexual shape dimorphism (SShD). Our analyses suggested that SShD is more stable than SSD, and that the scale of the focus (i.e. whole body proportions versus morphological details) is a key factor to test this notion. When general measurements were considered, the expected consistency of SShD between populations was verified; nevertheless, when more specific morphological attributes were considered, substantial variations were observed. These results provide a baseline for comparisons between populations to further examine geographic variation of sexual dimorphism.