On the trail of inter-species crosses: Although domestic and wild cats can produce offspring together, there was hardly any hybridization during their approximately 2,000 years of co-existence in Europe. This is shown by an examination of paleogenetic material from finds of both species. The rare pairings are probably mainly due to differences in behavior. As the example of Scotland makes clear, when populations of wild cats are critically small, problematic mixing eventually occurs, the scientists report.
Although they are similar, they are clearly two different species: The European wildcat (Felis silvestris) roamed our forests long before humans established “his kitty” in their habitat. The domestic cat (Felis catus) goes back primarily to the brown cat (Felis lybica), which is widespread in North Africa and the Middle East. From around 2000 years ago, humans brought domestic animals to the farthest corners of Europe. Since then it has shared its range with the native European wildcat. Since the two species can produce fertile offspring together, it stands to reason that hybridization could have occurred early on. However, the extent to which “cheating” took place over the course of centuries of co-existence remains unclear.
On the trail of feline “infidelities”.
An international team of researchers has now addressed this question using paleogenomics. The scientists obtained genetic material from wild and domestic cats: it came from 48 modern individuals and 258 domestic or wild cats that lived up to 8,500 years ago. These were remains from archaeological sites in various parts of Europe, which could be classified in time using radiocarbon dating. The genetic material obtained was then sequenced, analyzed and compared. Using certain genetic traces, it was possible to demonstrate the extent to which there had been gene flow between the two cat species over the last 2,000 years.
As the team reports, their results make it clear that domestic and wild cats mixed surprisingly little over the course of their coexistence. This is reflected in the relatively low heritage of Felis silvestris in our current house cats: Less than ten percent of the ancestry of most modern domestic cats can be traced back to wild cats. In wildcats from the last 2,000 years, the researchers found no or only very small traces of hybridization in the genome. In retrospect, the results confirm modern evidence that the two species at least normally avoid mating.
“Our studies show that the biology of domestic cats differs so much from that of wild cats that they would be unlikely to interbreed,” says senior author Laurent Frantz from the Ludwig Maximilian University of Munich. “This is probably because domestic cats and wild cats have adapted to very different ecological niches and display different behaviors: One aspect is that wild cats are more solitary animals, while domestic cats can live in much higher densities,” says Frantz.
Small populations encourage hybridization
According to the researchers, however, it is becoming apparent that the long-term reproductive isolation is currently being broken down by human influences in some parts of the wild cat's range. When the population of the species becomes very small due to disturbance or fragmentation of the habitat, the wild cats also get involved with domestic cats due to a lack of intraspecific partners.
This is particularly clear in the case of Scotland's stocks. Separation there has been dwindling, especially since the 1960s, as scientists were able to show in a separate study led by the University of Bristol. This means that the wildcat there is increasingly at risk of becoming a wild domestic cat and thus losing its species identity. “This hybridization is a consequence of modern threats. Habitat loss and persecution have brought the wildcat to the brink of extinction in Great Britain,” says Jo Howard-McCombe, lead author of the Scottish wildcat study.
The scientists say that the new findings can now help to better protect the species in the future, for example with regard to protection programs and reintroductions. For Germany, current results indicate that the populations are not yet exposed to the same hybridization pressure. Nevertheless, attention to the problem is warranted. Frantz concludes: “We would need more genomic data to be able to monitor the situation in the future and prevent us from being confronted with the same problems as in Scotland.”
Source: Ludwig Maximilian University of Munich, University of Oxford, specialist article: Current Biology, doi: 10.1016/j.cub.2023.08.031