High prevalence of accessory scutes and anomalies in Iberian populations of Emys orbicularis

Abstract

In a previous paper we found that most individuals from two populations of E. orbicularis from NW Spain had accessory scutes and other anomalies in their carapace. In this paper we analyze 10 additional populations [Ribadavia, NW Spain, Boticas (N Portugal), Castro Verde and Almograve (S Portugal), Salamanca and Zamora (Central-West Spain), Madrid (Central Spain), Ciudad Real (Central-Southern Spain), Doñana National Park (SW Spain) and Valencia (E Spain)] and increase previous samples from NW Spain. We found that the proportion of anomalous specimens oscillates between 3% in Doñana and 69% in Porriño. The incidence of anomalies varies significantly between populations, and there is a tendency for an increase of these anomalies from South to North. Non-Iberian populations of E. orbicularis rarely show anomalous individuals (except for some areas of Poland and Belarus). In other turtle species these anomalies seem to be due mainly to suboptimal humidity and temperature conditions during incubation. We suggest that the high prevalence of anomalies in Iberian populations of E. orbicularis might be due to a genetic predisposition of Iberian lineages, but other explanations based on the effects of pollution and problems due to the loss of genetic variability in Northern populations might also contribute to the frequency of this trait.