Microenvironment, reproductive tactics and morphology in Mediterranean <i>Salamandra</i>

The genus Salamandra encompasses several species of terrestrial salamanders distributed throughout the Western Palaearctic ecoregion. These salamanders exhibit substantial variation in their colouration patterns, ranging from almost entirely black to yellow, as well as in their reproductive strategies, with some populations showing direct development of juveniles. This study investigates the mechanisms underlying the phenotypic variation among five species of the genus Salamandra: Salamandra algira Bedriaga, 1883, Salamandra atra Laurenti, 1768, Salamandra corsica Savi, 1838, Salamandra lanzai Nascetti, Andreone, Capula, and Bullini, 1988, and Salamandra salamandra (Linnaeus, 1758), and 16 subspecies. Microclimatic conditions of their habitats were monitored using temperature and humidity probes across 78 sites over a minimum period of 1 year. Blomberg’s K indicated that the diversification in thermal niches is phylogenetically constrained, with closely related subspecies occupying environments with similar maximum temperatures. Direct juvenile development and atypical patterns of body colouration (predominantly yellow or black) occur in habitats with higher environmental humidity. However, larviparous and typical coloured morphs can also be present in habitats with comparable humidity levels. This suggests that while high humidity may not be the sole factor driving these divergences, it could facilitate shifts into new environmental niches and the emergence of novel adaptive phenotypes.