This paper was written under Project2007–2010(Estacion Biologica de Doñana, CSIC/Principado de Asturias), while J.E.S. was a visiting scientist at Estación Biológica de Doñana, supported by the Junta de Andalucía; and T.P. and A.D. are researchers in the Genetics Project (University of Oviedo/Principado de Asturias). A.O. was funded by the Fundación Oso de Asturias.