Name: Pereira P

Biodeserts supervisor: Velo-Antón G

Co-supervisor: Teixeira J

Title: Biogeographical history and range expansion dynamics of the European pond turtle

Institution: University of Porto

Status: Completed

 

Abstract

The complex paleogeographic history of the Mediterranean Basin allowed for high levels of biodiversity in the region. In fact, several endemism occur in the area, granting the Mediterranean Basin the status of hotspot for biodiversity. For example, events such as the Messinian Salinity Crisis, that lead to the partial dissection of the Mediterranean Sea, which in turn allowed for species to cross between Europe and Africa; and the Glacial-Interglacial cycles that promoted range shifts in several Temperate species while tracking for suitable habitat, promoted in one hand Vicariance events between several species, while in the other hand allowed for secondary contact zones to occur after species expanded from their Glacial refugias during climate amelioration. Furthermore, the role of the European Peninsulas and the Maghreb as refugia during Glacial periods promoted allopatric diversification as different populations of a same species would sometimes take refuge in different glacial refugia therefore allowing for the diversification between them.

The European pond turtle, Emys orbicularis, alongside its sister taxa, Emys trinacris, are the only representatives of the Emys genus in the old world. Emys orbicularis occurs widely throughout Europe, with populations reaching Asia, and North-western part of Africa. Currently 9 distinct mitochondrial lineages have been found using the cytochrome b gene. Nonetheless, across its entire range, demographical contractions have been noticed and prompted several conservation measures.

One of the described lineages is native to the Ibero-Maghbreian region, and has been subject of a lot of interest due to its very complex biogeographical history. Two different patterns arise in light of different data. Fossil records seem to indicate a longer presence of Emys orbicularis in the Iberian Peninsula when compared to the Maghreb. However, in light of genetic data, the hypothesis of a colonization of the Iberian Peninsula from North Africa seems more likely.

With this work we aim to reinforce the current knowledge on the species biogeographical history of the species and to assess the role of the past climatic oscillations, and more specifically, the role that range expansions and contractions that occurred during the Quaternary to the Holocene, had on the current pattern of genetic structure. To do so both slow and fast evolving markers were here used (cytochrome b and microsatellites respectively) in an attempt to understand the directionality of the expansion and its consequences at the level of the genetic structure.

The addition of 80 new sequences to the already large data collected for this species allowed for the first time the detection of African haplotypes in the Iberian Peninsula, also the fact that North African populations show higher levels of genetic structure and diversity lead to a further support of North Africa as the origin for the Ibero-Maghrebian lineage. As for the role that range expansions had in shaping the current patterns of genetic diversity and structure, we found strong signs of allelic frequency clines alongside the axis of expansion, and a strong decrease in genetic diversity. Furthermore, the strong genetic structure present in the Northwest of the Iberian Peninsula seems to be concordant with known consequences of range expansions.

Overall, this study allowed for the first time a complete survey of the effects that the range expansions from southern refugia had in the Iberian Peninsula. Furthermore, the collected genetic data permitted us to improve a tool for the genetic allocation of individuals of unknown origin to a probable putative population of origin.