Wolf dog hybridization in Croatia
Wolf dog hybridization is considered as one of the main threats for wolf conservation since the admixture and introgression of domestic genes may disrupt local adaptations and threaten the long term survival of wild wolf populations. We investigated the occurrence of wolf dog hybridization in Croatia by analyzing a panel of 12 autosomal microsatellite markers using Bayesian admixture tests, and assessed its directionality by the use of maternally and paternally inherited markers in combination with morphometric data and morphological features. A systematic analysis of morphologic features and morphometric data was used to rank the studied individuals into either phenotypic wild type wolves or suspected hybrids. By combining Bayesian assignment results with phenotypic features, we set three thresholds which differentiated wolves from hybrids with maximized hybrid detection and a minimized chance for false positive hybrid identification. On the basis of phenotype, out of 176 wild canids, 157 (89.2% were categorized as wolves and 19 (10.8% as suspected hybrids. On the basis of the Bayesian admixture tests and phenotype together, five (2.8 percent) animals were classified as wolf dog hybrids, four of them as backcrosses with wolves, and one as a backcross with a dog. Mitochondrial DNA suggested that all hybrids originated from the mating of female wolves and male dogs. Two male hybrids had Y chromosome haplotypes common to both wolves and dogs, while the other two had wolf private Y chromosome haplotypes. One wolf had a dog Y haplotype, indicating a past introgression of dog genes. All hybrids were found in Dalmatia, where wolves settled recently, and where they live close to humans, with a high rate of human caused mortality. These conditions are considered as favorable for wolf dog hybridization. However, we found a low hybridization prevalence in Croatia, which is nonetheless expected to persist as long as the conditions favoring its occurrence are met. The ecological, sociological, conservation and management implications of hybrid occurrence are yet to be determined.