Abstract
Hybridisation between a domesticated species and its wild ancestor is an important conservation problem, especially if it results in the introgression of domestic gene variants into wild species. Nevertheless, the legal status of hybrids remains unregulated, partially because of the limited understanding of the hybridisation process and its consequences. The occurrence of hybridisation between grey wolves and domestic dogs is well documented from different parts of the wolf geographic range, but little is known about the frequency of hybridisation events, their causes and the genetic impact on wolf populations. We analysed 61K SNPs spanning the canid genome in wolves from across Eurasia and North America and compared that data to similar data from dogs to identify signatures of admixture. The haplotype block analysis, which included 38 autosomes and the X chromosome, indicated the presence of individuals of mixed wolf–dog ancestry in most Eurasian wolf populations, but less admixture was present in North American populations. We found evidence for male‐biased introgression of dog alleles into wolf populations, but also identified a first‐generation hybrid resulting from mating between a female dog and a male wolf. We found small blocks of dog ancestry in the genomes of 62% Eurasian wolves studied and melanistic individuals with no signs of recent admixed ancestry, but with a dog‐derived allele at a locus linked to melanism. Consequently, these results suggest that hybridisation has been occurring in different parts of Eurasia on multiple timescales and is not solely a recent phenomenon. Nevertheless, wolf populations have maintained genetic differentiation from dogs, suggesting that hybridisation at a low frequency does not diminish distinctiveness of the wolf gene pool. However, increased hybridisation frequency may be detrimental for wolf populations, stressing the need for genetic monitoring to assess the frequency and distribution of individuals resulting from recent admixture.
Highlights
Hybridisation between defined taxonomic entities can be an important conservation problem when it involves an invasive and a native species, or a domesticated subspecies and its wild ancestor (Wayne & Shaffer, 2016)
The occurrence of hybridisation between grey wolves and domestic dogs is well-documented from different parts of the wolf geographic range, but little is known about the frequency of hybridisation events, their causes and the genetic impact on wolf populations
We carried out ancestry block analyses in Eurasian wolves in comparison with domestic dogs, applying a method implemented in the LAMP software that did not require the use of non-admixed reference populations
Summary
Hybridisation between defined taxonomic entities can be an important conservation problem when it involves an invasive and a native species, or a domesticated subspecies and its wild ancestor (Wayne & Shaffer, 2016). Rapid human population growth and the spread of human-modified habitats can result in a parallel increase in domesticated species and decline of their wild relatives. Such changes in relative densities can increase the frequency of hybridisation, resulting in extensive introgression of derived “domesticated” gene variants into wild populations. Admixture between free-living Soay sheep and a modern sheep (Ovis aries) breed resulted in an introgression of a TYRP1 gene variant associated with light coat colour, which was favoured by natural selection in Soay sheep (Feulner et al, 2013) Another example comes from Alpine ibex (Capra ibex ibex), which was shown to acquire one of its two MHC DRB alleles from domestic goats (Capra aegagrus hircus) (Grossen et al, 2014). Our understanding of the hybridisation process and its consequences is still limited, and improving this knowledge has both theoretical importance (for understanding the role of hybridisation in speciation and adaptation) and practical applications in wildlife conservation and management of feral domestic populations
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