In two related studies, researchers from the University of Oxford and elsewhere sequenced the genomes of wildcats and domestic cats, including 48 modern individuals and 258 ancient samples excavated from 85 archaeological sites over the last 8,500 years. They then assessed the patterns of hybridization after domestic cats were introduced to Europe over 2,000 years ago and came into contact with native European wildcats. Their results demonstrate that, since their introduction, domestic cats and European wildcats generally avoided mating. About 50 years ago in Scotland, however, that all changed. Perhaps as a result of dwindling wildcat populations and a lack of opportunity to mate with other wildcats, rates of interbreeding between wild and domestic cats rose rapidly.
The European wildcat (Felis silvestris). Image credit: Michael Gäbler / CC BY 3.0 Deed.
Domestic cats (Felis catus) were derived from the Near Eastern wildcat (Felis lybica), after which they dispersed with people into Europe.
As they did so, it is possible that they interbred with the indigenous population of European wildcats (Felis silvestris).
Gene flow between incoming domestic animals and closely related indigenous wild species has been previously demonstrated in other species, including pigs, sheep, goats, bees, chickens, and cattle.
In the case of cats, a lack of nuclear, genome-wide data, particularly from Near Eastern wildcats, has made it difficult to either detect or quantify this possibility.
To address these issues, the authors generated 75 ancient mitochondrial genomes, 14 ancient nuclear genomes, and 31 modern nuclear genomes from European and Near Eastern wildcats.
Their results demonstrate that despite cohabitating for at least 2,000 years on the European mainland and in Britain, most modern domestic cats possessed less than 10% of their ancestry from European wildcats, and ancient European wildcats possessed little to no ancestry from domestic cats.
“Wildcats and domestic cats have only hybridized very recently,” said Dr. Jo Howard-McCombe, a researcher at the University of Bristol and the Royal Zoological Society of Scotland.
“It is clear that hybridization is a result of modern threats common to many of our native species.”
“Habitat loss and persecution have pushed wildcats to the brink of extinction in Britain.”
“It is fascinating that we can use genetic data to look back at their population history, and use what we have learnt to protect Scottish wildcats.”
In the second study, the researchers generated and analyzed whole-genome sequence data to date the onset of significant hybridization in Britain and assess potential consequences for wildcats carrying introgressed domestic cat DNA.
The data comprised 22 domestic cats, 30 wild-living individuals from Scotland sampled across the hybrid swarm, and six wildcats from the UK captive population (founded on wild animals from Scotland). Seven additional wildcat samples were obtained from Germany and Portugal.
The scientists also made use of low-coverage, whole-genome sequence data from historic and archaeological samples, specifically four putative Scottish wildcats and two archaeological samples from Medieval and Mesolithic Britain.
Additional low-coverage genomic data were obtained from 20 museum samples of putative Scottish wildcats.
“We tend to think of cats and dogs as very different,” said University of Oxford’s Professor Greger Larson.
“Our data suggest that, at least with respect to avoiding interbreeding with their wild counterparts, dogs and cats are much more similar to each other than they are to all other domestic animals. Understanding why this is true will be fun to explore.”
“The nature of the Scottish wildcat and its relation to feral domestic cats has long been a mystery,” said University of Bristol’s Professor Mark Beaumont.
“Modern molecular methods and mathematical modeling have helped to provide an understanding of what the Scottish wildcat truly is, and the threats that have led to its decline.”
The findings were published in the journal Current Biology.
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Alexandra Jamieson et al. 2023. Limited historical admixture between European wildcats and domestic cats. Current Biology 33 (21): 4751-4760; doi: 10.1016/j.cub.2023.08.031
Jo Howard-McCombe et al. 2023. Genetic swamping of the critically endangered Scottish wildcat was recent and accelerated by disease. Current Biology 33 (21): 4761-4769; doi: 10.1016/j.cub.2023.10.026
