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

Abstract

Anthropogenic hybridization is widely perceived as a threat to the conservation of biodiversity. Nevertheless, to date, relevant policy and management interventions are unresolved and highly convoluted. While this is due to the inherent complexity of the issue, we hereby hypothesize that a lack of agreement concerning management goals and approaches, within the scientific community, may explain the lack of social awareness Donfrancesco et al.Addressing Wolf-Dog Hybridization in Europe on this phenomenon, and the absence of effective pressure on decision-makers. By focusing on wolf x dog hybridization in Europe, we hereby (a) assess the state of the art of issues on wolf x dog hybridization within the scientific community, (b) assess the conceptual bases for different viewpoints, and (c) provide a conceptual framework aiming at reducing the disagreements. We adopted the Delphi technique, involving a three-round iterative survey addressed to a selected sample of experts who published at Web of Science listed journals, in the last 10 years on wolf x dog hybridization and related topics. Consensus was reached that admixed individuals should always be defined according to their genetic profile, and that a reference threshold for admixture (i.e., q-value in assignment tests) should be formally adopted for their identification. To mitigate hybridization, experts agreed on adopting preventive, proactive and, when concerning small and recovering wolf populations, reactive interventions. Overall, experts' consensus waned as the issues addressed became increasingly practical, including the adoption of lethal removal. We suggest three non-mutually exclusive explanations for this trend: (i) value-laden viewpoints increasingly emerge when addressing practical issues, and are particularly diverging between experts with different disciplinary backgrounds (e.g., ecologists, geneticists); (ii) some experts prefer avoiding the risk of potentially giving carte blanche to wolf opponents to (illegally) remove wolves, based on the wolf x dog hybridization issue; (iii) room for subjective interpretation and opinions result from the paucity of data on the effectiveness of different management interventions. These results have management implications and reveal gaps in the knowledge on a wide spectrum of issues related not only to the management of anthropogenic hybridization, but also to the role of ethical values and real-world management concerns in the scientific debate.

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

“…Our multiple-criteria approach can help wildlife managers and decision makers in more efficiently targeting the available resources for the long-term conservation of species threatened by anthropogenic hybridization.Over the last decades, thanks to the growing availability of genetic and genomic data, hybridization has been increasingly studied for its evolutionary and conservational implications on the long-term survival of the involved taxa 1-5 . However, while natural hybridization between closely related taxa is frequently acknowledged as an evolutionary process providing novel adaptive gene assemblages 6,7 , anthropogenic hybridization (AH), mainly caused by intentional admixture, translocations, habitat modifications and climate changes 8-10 , is globally considered a serious conservation threat to the genetic integrity of local populations, which might be compromised by gene introgression from alien or domesticated species [11][12][13][14][15][16] . Thus, the consequences of such human-mediated process should be continuously monitored to evaluate their real effects on the viability of natural populations 5,17 .However, to date, even in the era of genomics 4,18 , the concept of hybrid itself is rather fleeting and, consequently, legal status and management of hybrids are often poorly regulated by national and international laws, hampering the conservation of endangered species 12,14,[19][20][21][22]…”

“…Over the last decades, thanks to the growing availability of genetic and genomic data, hybridization has been increasingly studied for its evolutionary and conservational implications on the long-term survival of the involved taxa 1-5 . However, while natural hybridization between closely related taxa is frequently acknowledged as an evolutionary process providing novel adaptive gene assemblages 6,7 , anthropogenic hybridization (AH), mainly caused by intentional admixture, translocations, habitat modifications and climate changes 8-10 , is globally considered a serious conservation threat to the genetic integrity of local populations, which might be compromised by gene introgression from alien or domesticated species [11][12][13][14][15][16] . Thus, the consequences of such human-mediated process should be continuously monitored to evaluate their real effects on the viability of natural populations 5,17 .…”

“…feasible conservation strategy 3,16,21,23,24 , or which methods should be applied for their control (e.g. sterilization, captivation, lethal removal).…”

“…sterilization, captivation, lethal removal). Finally, it is still uncertain whether admixed individuals originated from hybridization events that occurred several generations in the past should be targets of management actions 10,16,[24][25][26] , especially when they retain likely adaptive variants (e.g. the black coat in wolves 27 and the domestic goat MHC haplotypes in the Alpine ibex 28 ).…”

“…Furthermore, particular attention should be reserved to the choice of adequate statistical computations for the assignment procedures, in order to minimise the risk that individual assignment probabilities might be affected by the allele frequencies of other samples to be assigned. In addition, the selection of statistically supported assignment q-thresholds based on individual assignment (q i -values) extrapolated from simulated data is necessary to ensure the realistic and reliable identification of admixed individuals 5,16,[40][41][42] .…”