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Phylogenetic Study Suggests European Origins for Australian Feral Cats

NEW YORK (GenomeWeb) — Australia's feral cats are largely descended from cats that came ashore a couple centuries ago, according to a study published online today in BMC Evolutionary Biology.

Researchers from Germany, Australia, and the US did a phylogenetic study of feral cats from Australian islands, the Australian mainland, and Asia. Through a phylogenetic analysis of the animals and dozens of other cats previously tested from sites in Europe, they pinned the roots of feral cat populations in Australia to felines introduced by European settlers in the 19th century.

The team suspects these animals migrated throughout Australia, before admixing in mainland Australia and Tasmania with cats introduced to the continent more recently from Europe and Asia.

"Taken together with historical record, the genetic data suggest introduction of cats to Australia mainly following European settlements, providing an important timeframe for the impact of feral cats on native species in Australia," the authors wrote. "Further precision may be possible with more detailed (genomic scale) data and a search for archaeological specimens, which themselves may be subject to genetic analysis."

Although domesticated thousands of years after dogs, cats have managed to make their way to sites around the world, often aboard ships by humans who put them to work keeping rodent populations under control. These once-domestic or semi-domestic cats are believed to be the potential ancestors of feral cat populations in various parts of the world, though there is ongoing debate about the precise source and timing of such introductions.

In the case of Australia's feral cats, the team noted, this introduction may have occurred thousands of years ago, though it's more commonly thought the animals arrived alongside Malaysian fishermen or shipwrecked Europeans in the 1600s, or with European settlers in the 18th century.

To pin down the animals' genetic origins, the researchers collected samples from 269 feral cats living in seven Australian islands, six sites on the Australian mainland, and one location in Malaysia, and used Sanger sequencing to profile a dozen microsatellite markers and more than 2,600 bases of mitochondrial sequences.

Based on data from these mitochondrial sequences and 11 of the microsatellite markers, the team found that feral cats on several islands — including Christmas Island, Cocos Island, Dirk Hartog Island, Flinders Island, and Tasman Island — fell in a handful of clusters apart from the more genetically diverse feral cats on mainland Australia and Tasmania.

Using mitochondrial haplotype patterns present in the Australian animals and their counterparts from Europe and Asia, the researchers identified two main cat clades. The distribution and sources of haplotypes within in the clades pointed to an original cat population from West-Central Europe, likely arriving by sea with Europeans in the early 19th century.

In mainland Australia and Tasmania, where current feral cat populations are more genetically diverse, the team saw hints of more recent admixture, perhaps due to mixing with new arrivals from Europe or Asia and escaped house cats. On the other hand, it did not find evidence for a solely Asian source for feral cats.

"There is an indication of bidirectional movement of cats between Australia and Asia additional to the European colonization," they wrote. "However, caution is needed in inferring the involvement of Asian cats in the history of cat colonization in Australia due to the small number of Asian samples."