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Universidade do Porto (2014)

Phylogeography and current patterns of genetic diversity and structure of the Mediterranean pond turtle

Joana Filipa da Silva Veríssimo

Titre : Phylogeography and current patterns of genetic diversity and structure of the Mediterranean pond turtle

Auteur : Joana Filipa da Silva Veríssimo

Université de soutenance : Universidade do Porto

Grade : Mestrado em Biodiversidade, Genética e Evolução 2014

Résumé
The complex palaeogeographic history of the Mediterranean Basin lead to the high levels of diversity and endemisms in the area, as of that, this region is now included in the 25 global hotspots of biodiversity. For instance, the Milankovitch climatic oscillations induced range retractions to the Southern European Peninsulas and the Maghreb, where temperate species found refuge, allowing them to survive the colder periods. This process also induced allopatric diversification in some species as different populations took refuge in different regions and so became isolated. Ectothermic species depend on climate induced temperatures to survive, making them more susceptible to suffer retraction/expansion events during those times of climatic instability. The Mediterranean pond turtle, Mauremys leprosa, occurs widely throughout the Iberian Peninsula and most of the Maghreb region. Currently, two subspecies are recognized : M. l. saharica (ranging from southern of the Atlas Mountains to Tunisia) and M. l. leprosa (northern of the Atlas Mountains and in the Iberian Peninsula). For this work, we aim to explore the effect that past climatic oscillations and landscape barriers produced in the current patterns of genetic diversity and structure of M. leprosa, to do so, we used two fragments of mitochondrial DNA. Also, we intend to assess population genetic patterns and structure within this species at a more recentscale. As of that, microsatellite loci were here optimized for the first time for Mauremys leprosa by cross-amplification of two closely related species. Mitochondrial DNA (cyt-b and D-loop), retrieved from 163 specimens, showed deep genetic structure and higher levels of genetic diversity in North Africa, reinforcing the hypothesis of an African origin of the Iberian populations. Moreover, a secondary contact zone within the species was found in the Rif and Middle Atlas region. Microsatellite loci (genotyped in 556 individuals) revealed lower genetic structure in Morocco than in the Iberian Peninsula. However, for the latter, no geographical patterns were found. Furthermore, the high levels of genetic diversity found in southern populations of Iberian Peninsula might indicate a late Pleistocene refugia in the area, however, further studies are needed to clarify the role of this area during climatic oscillations. Regarding the secondary contact zone, this fast evolving marker revealed gene flow between the subspecies. Overall, this study sheds new light into the role of both geographical and climatic features on the genetic diversity and structure patterns of Mauremys leprosa, complementing the current knowledge on the importance of North Africa as a refugia.

Mots clés  : Biogeography, Climatic Oscillations, Glacial Refugia, Iberian Peninsula, Maghreb, Mauremys leprosa, Microsatellites, mtDNA, Phylogeography, Secondary contact zones.

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