Two Holocene refugia for European domestic horses

I find the especially high genetic diversity in the Caspian horse to be particularly interesting in conjunction with some of my recent speculations.

The authors write:

Our investigation of genetic diversity in traditional European horse breeds reveals two hotspots of genetic diversity, one in the Caspian region of western Asia and one in the Iberian Peninsula. The distribution of high genetic diversity in European horses coincides with the distribution of open vegetation in the mid-Holocene, suggesting that these areas acted as refugia for wild horses at a time when most of Europe was covered by dense forest [25].

Although our lack of sampling locations in Central and East Asia prevents us from pinpointing primary areas of horse domestication in this region, high diversity in the Caspian area is in agreement with palaeontological data suggesting that E. ferus survived the Holocene in South-West Asia and Central Asia [26]. Additional sampling further east will help establish whether there is a genuine hotspot of genetic diversity in the Caspian region or whether high diversity in this region merely reflects generally higher levels of diversity in the Eurasian steppes.

PLoS ONE 6(3): e18194. doi:10.1371/journal.pone.0018194

European Domestic Horses Originated in Two Holocene Refugia

Vera Warmuth

Abstract

The role of European wild horses in horse domestication is poorly understood. While the fossil record for wild horses in Europe prior to horse domestication is scarce, there have been suggestions that wild populations from various European regions might have contributed to the gene pool of domestic horses. To distinguish between regions where domestic populations are mainly descended from local wild stock and those where horses were largely imported, we investigated patterns of genetic diversity in 24 European horse breeds typed at 12 microsatellite loci. The distribution of high levels of genetic diversity in Europe coincides with the distribution of predominantly open landscapes prior to domestication, as suggested by simulation-based vegetation reconstructions, with breeds from Iberia and the Caspian Sea region having significantly higher genetic diversity than breeds from central Europe and the UK, which were largely forested at the time the first domestic horses appear there. Our results suggest that not only the Eastern steppes, but also the Iberian Peninsula provided refugia for wild horses in the Holocene, and that the genetic contribution of these wild populations to local domestic stock may have been considerable. In contrast, the consistently low levels of diversity in central Europe and the UK suggest that domestic horses in these regions largely derive from horses that were imported from the Eastern refugium, the Iberian refugium, or both.

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