Wolf-dog hybridization in Croatia

Abstract

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.

A standardized approach to empirically define reliable assignment thresholds and appropriate management categories in deeply introgressed populations

“…The selection of a sufficient number of non-admixed parental individuals to use as reference populations in the assignment analyses was made possible by testing a large national database that includes hundreds of individuals sampled from the entire subspecies distribution range, which had been all formerly morphologically described and molecularly characterized at different sets of genome-wide (STRs and SNPs) markers 26,33,52 . Therefore, initiatives aiming at systematically collecting population-wide samples of target species should be strongly sustained by national or local authorities, possibly including also samples from nearby populations in order to take into account possible gene flows 22,68 and, whenever achievable, detailed information on possible phenotypical anomalies 5,24,26 .…”

“…Conversely, most genetic investigations about hybridization in canids were mainly based on q-thresholds selected arbitrarily or chosen among those widely used in the literature (e.g. Malde et al 41 ) and rarely using simulated data to estimate error rates associated to the choice of a certain threshold 31,33,37,66,68,74 . A third challenge is thus represented by the adoption of objective criteria based on a Performance Analysis 38 for setting the most appropriate q-thresholds to classify individuals into different admixture classes (e.g.…”

Unravelling the Scientific Debate on How to Address Wolf-Dog Hybridization in Europe

“…Although we cannot dismiss the role that other confounding factors (e.g., age, gender, cultural background, country of origin, working context, perception of management issues) may play in affecting experts' opinions, we believe that the contrast between, and the commonalities within, disciplines that we observed reveal the overarching effect that the educational background and the field of expertise may have in shaping experts' points of view. This hints to an ongoing "paradigm shift" (i.e., the shift of intellectual frameworks of ideas; Kuhn, 1962) in conservation biology, whereby communities of scientists, each specialized in their own field, progressively develop intrinsically contrasting views on how to handle wildlife management problems. Embracing the idea of shifting paradigms is central to avoid alienating parts of the scientific community, and to promote a more unified scientific knowledge and wisdom, which is pivotal to effectively transmit a FIGURE 6 | Responses to a series of questions on wolf x dog hybridization by a selected group of experts, who self-identified themselves as either ecologists (n = 17) or geneticists (n = 17).…”

Living a dog’s life: a putative gray wolf in a feral dog group

“…This makes the current observation a first, opening a whole new dimension to the discussion surrounding the gray wolf's conservation in Europe. The presence of the aforementioned features in the putative wolf and its behavior might suggest that the individual is not a pure gray wolf but rather a wolf × dog hybrid, although it is very difficult to certainly conclude without genetic confirmation (Kusak et al 2018). This hypothesis is feasible due to the reportedly widespread hybridization in Bulgaria (Moura et al 2014), even among individuals with a typical gray wolf phenotype.…”

“…Apparently, the problem with wolf × dog hybridization in Bulgaria is serious and is part of a common concern for the genetic status of the wolves in Europe (Randi 2011). Hybridization has been reported in other parts of the continent, notably in Italy (Randi et al 2000, Verardi et al 2006, Iacolina et al 2010, Caniglia et al 2013, Latvia and Estonia (Andersone et al 2002, Hindrikson et al 2012, Scandinavia (Klütsch et al 2011, Vilà et al 2003, Serbia (Milenković et al 2006), the Iberian peninsula (Godinho et al 2011, Pacheco et al 2017, Torres et al 2017, Poland (Okarma 2015) and Croatia (Majić 2014, Kusak et al 2018. Once hybridization has occurred, it is difficult to stop it, especially when the hybrids are fertile (Allendorf et al 2001); thus their proportion in the population grows progressively.…”