Mitochondrial DNA variability in Italian and East European wolves: Detecting the consequences of small population size and hybridization

The Italian wolf (Canis lupus) population has declined continuously over th e last few centuries and become isolated as a result of the extermination o f other populations in central Europe and the Alps during the nineteenth ce ntury. In the 1970s, approximately 100 wolves survived in 10 isolated areas in the central and southern Italian Apennines. Loss of genetic variability , as suggested by preliminary studies of mitochondrial DNA (mtDNA) sequence s, hybridization with feral dogs, and the illegal release of captive, non-n ative wolves are considered potential threats to the viability of the Itali an wolf population. We sequenced 546 base pairs of the mtDNA control region in a comprehensive set of Italian wolves and compared them to those of dog s and other wolf populations from Europe and the Near East. Our data confir m the absence of mtDNA variability in Italian wolves: all 101 individuals s ampled across their distribution in Italy had the same, unique haplotype, w hereas seven haplotypes were found in only 26 wolves from an outbred popula tion in Bulgaria. Most haplotypes were specific either to wolves or dogs, b ut some east European wolves shared haplotypes with dogs, indicative of hyb ridization. In contrast, neither hybridization with dogs nor introgression of non-native wolves was detected in the Italian population. These findings exclude the introgression of dog genes via matings between male wolves and female dogs, the most likely direction of hybridization. The observed mtDN A monomorphism is the possible outcome of random drift in the declining and isolated Italian wolf population, which probably existed at low effective population size during the last 100-150 years. Low effective population siz e and the continued loss of genetic variability might be a major threat to the long-term viability of Italian wolves. A controlled demographic increas e, leading to recolonization of the historical wolf range in Italy, should be enforced.