Niche differentiation among genetic lineages in the Mediterranean Pond turtle, Mauremys leprosa, across its geographical range

Ecological niche modelling provides a useful tool to measure niche properties such as niche breadth, niche overlap and niche conservatism among genetic lineages, with relevant implications for conservation. The Mediterranean pond turtle Mauremys leprosa occurs on both sides of the Strait of Gibraltar over most Iberia and the Maghreb Region of north-western Africa, where it shows a complex genetic structure as the result of Pleistocene climatic oscillations and the particular geographical features of this region. We analyzed the overlap of the climate niche of genetic lineages and sublineages of Mauremys leprosa, based on confirmed records across the known geographical range of the species. We also compared the accuracy of environmental niche models obtained by splitting the two lineages into subunits and lumping across lineages. Results revealed an overall niche overlap between the two main lineages and among most sublineages, indicating no relationship between genetic variation and niche divergence. Likewise, the environmental niche modelling revealed an extensive geographical overlap of climatic suitability between the two lineages. However, some ecological differentiation occurs for some sublineage pairs, in particular involving a sublineage whose occurrence corresponds to a particular morphotype - the Sahara blue-eyed pond turtle - which occupies very isolated habitats along the Draa basin in Morocco. These populations are currently threatened by fragmentation of habitats, drought and water salinization. This study will help assessing more effectively the impacts of ongoing climate change on Mauremys leprosa that along with local human activities are likely to increase in the southernmost limit of its distribution.