The genetic integrity of the Italian wolf is increasingly threatened by hybridisation with domestic dogs. This phenomenon was demonstrated in a recent study conducted by Sapienza University of Rome in collaboration with the Tuscan-Emilian Apennines National Park, the Italian Institute for Environmental Protection and Research (ISPRA), and the Centre Nationale de la Recherche Scientifique (France), published in The Journal of Wildlife Management.

The domestic dog is the result of strong human selection and thousands of years of reproductive isolation from the wolf. Over time, the dog has developed forms and behaviour that are more appropriate to man's needs and profoundly different from its wild ancestor. From a biological point of view, the dog and the wolf are the same species and can mate and produce fertile hybrids under certain circumstances. Although hybridisation with the wolf has occasionally occurred since the origin of dog domestication, the fear today is that the phenomenon is undergoing a dramatic rise as the wolf spreads into more anthropised areas, where the numerical ratio is largely in favour of the dog population.

"Since the first rare sightings of hybrids in the 1970s and 1980s, the phenomenon has been largely underestimated in subsequent years" - says the study coordinator Paolo Ciucci of the Department of Biology and Biotechnology "Charles Darwin" of Sapienza University of Rome. "This is due both to the technical difficulties involved in identifying hybrid individuals, including subsequent generations of backcrosses and to the complex and delicate management implications of the phenomenon. Furthermore, to date, few studies have actually quantified wolf-dog hybridisation according to population parameters and adequate statistical models, while the tools now available allow us to produce more accurate estimates."

Based on 152 samples collected from 39 wolves in 7 different packs, the researchers estimated a hybrid prevalence of 70%, with hybrids present in at least 6 of the 7 monitored packs. Furthermore, through genealogical reconstruction, it was found that in at least two of these packs, hybrids have breeding status and are therefore able to pass on genetic variants of canine origin to subsequent generations. 

Although hybridisation cases were originally hypothesised, considering the potentially negative effects that genes of canine origin can have on the survival of the wolf in the wild, the results of the study highlight an alarming scenario for the conservation of the species and the protection of its genetic identity.

"We were able to produce an accurate estimate of the phenomenon on a local scale, thanks to a network of collaborators with complementary skills, which allowed us to apply appropriate sampling strategies, together with formal methods of demographic estimation and particularly efficient techniques of genetic diagnosis"- adds Nina Santostasi, researcher of the same Department and first author of the study. "The results emphatically highlight that the presumed behavioural reproductive barriers between dogs and wolves, or the dilution of canine-derived genes in the wolf population, are not in themselves sufficient to prevent hybridisation and its spread within the wolf population. Unfortunately, in all likelihood, this situation is not limited to the area in which we have been working, and it is essential to urgently replicate the same type of study in other areas of the species' range."

The paper shows how crucial it is not to ignore the phenomenon and to deploy all the best management skills and expertise to preserve wolves' genetic integrity. Besides, it is necessary to inform and raise public awareness of the risk of genomic extinction. "This is a concept that is much more difficult to understand and share than the risk of demographic extinction when, in the early 1970s, Italy advocated legal protection for the species," Ciucci concludes. "Paradoxically, 50 years later, it is the same genetic identity of the wolf that is put at risk as a consequence of the expansive dynamics of the species, of the high number of stray dogs and management intertia."

The genetic techniques used by the researchers to identify the hybrids using DNA extracted from wolf droppings were developed in the Genetica della Conservazione laboratory of the Italian Institute for Environmental Protection and Research (ISPRA) which has been working in this field for many years.

The estimate of the prevalence of hybrids was carried out in the wolf population living in the Tuscan-Emilian Apennine National Park and in the surrounding areas of the northern Apennines, a central and strategic area of wolf distribution in the Apennines, where the first hybrids, or individuals morphologically deviant from the wolf's morphological standard, had already been observed since the end of the 1990s.

References:

Estimating Admixture at the Population Scale: Taking Imperfect Detectability and Uncertainty in Hybrid Classification Seriously - Nina L. Santostasi, Olivier Gimenez, Romolo Caniglia, Elena Fabbri, Luigi Molinari, Willy Reggioni, Paolo Ciucci - The Journal of Wildlife Management https://doi.org/10.1002/jwmg.22038

Further Information

Paolo Ciucci
Department of Biology and Biotechnology "Charles Darwin"
paolo.ciucci@uniroma1.it