Genetic and morphometric evidence of introgressionbetween two species of moles (Insectivora: Talpa europaea and Talpa romana) in central Italy

Abstract

Allozyme and morphometric variation was studied in two populations of moles, Talpa europaea and T. romana, in an area of sympatric occurrence (Palazzo, near Assisi, central Italy) located along the known parapatric contact boundary. The electrophoretic analysis revealed 36 moles characterized by a genome of T. europaea, and 29 moles with a genome of T. romana. The extension of the overlap zone was c. 2 km along the north–south direction. Fourteen specimens recognized as T. europaea had an Ada allele typical of T. romana, while two specimens identified as T. romana were characterized by two alleles (at the Adh and Sdh loci) previously found only in T. europaea. The skulls of the specimens with introgressed alleles showed features intermediate between those typical of T. romana and T. europaea. However, the intermediate skull shape of the introgressed specimens did not correspond to an intermediate size between T. romana and T. europaea. The occurrence of individuals with introgressed alleles, and the lack of F₁ hybrids or backcrossed individuals suggest that at present free interbreeding between the two species is unlikely, but that hybridization and backcrossing has occurred, probably when the species first came into contact.