Sexual dimorphism in digit ratio in Tropidurus catalanensis: relations to climatic parameters

Abstract

Occupancy of distinct environments in relation to thermal gradients can affect development processes and result in phenotypic variation that may influence survival and reproductive rates. Particularly, digit ratio is a morphological characteristic that can be sexually dimorphic and it has been evaluated in some groups as an indicator of embryonic developmental mechanisms that are mediated by esteroid hormones. The pattern of dimorphism in this feature seems variable inside the Squamate group, and its analysis may provide informations about the hormonal environment during development and its relations to environmental variable, as differences in thermal regimes. Althoug the relation between temperature and hormones is expected, associations including digit ratio and thermal regimes during the embryonic development are not explored in Squamata, particularly in this context of sexual dimorphism in lizards populations distributed along a latitudinal gradient with variations in temperature. This study aims to investigate if populations of Tropidurus catalanensis lizards distributed in a latitudinal gradient show differences in dimorphic patterns of digit ratio, adding to this evaluation the experimental approach with manipulations of thermal regimes during the embryonic development in laboratory. Measures of digit length will be obtained in males and females of T. catalanensis available in herpetological collections. In addition, pregnant T. catalanensis females will be collected and transported to Laboratory of Evolution and Integrative Biology (LEBI-USP) to get clutch. The eggs will be incubated in different thermical conditions and digit ratio will be evaluated in males and females neonates. These complementary approaches enable to integrate patterns of sexual dimorphism in lizards digit ratio to environmental parameters (temperature and latitude) under the innovative perspective of Eco-evo-devo. (AU)