Mitochondrial diversity of the widespread Central Asian steppe tortoise (Testudo horsfieldii Gray, 1844): implications for taxonomy and relocation of confiscated tortoises

Abstract Using a nearly range-wide sampling, we investigated phylogeographic differentiation and mitochondrial diversity of Testudo horsfieldii, the only tortoise species confined to Central Asia. We identified three major haplotype clades with mainly parapatric distribution that do not correspond well to the currently recognized three subspecies. One clade is restricted to the Fergana Valley and seems to represent a previously overlooked evolutionarily significant unit. Another clade, consisting of several largely parapatrically distributed haplotypes, occurs in the north and the central southern part of the species' range. The third clade, likewise comprising several largely parapatrically distributed haplotypes, was identified from the south-eastern corner of the Caspian Sea in the west, from Afghanistan and Pakistan in the east and from two more northerly sites in western and south-eastern Uzbekistan. It is possible that this clade also occurs in eastern Turkmenistan and adjacent Afghanistan, regions not sampled for the present study. The generally parapatric distribution of individual haplotypes, even within each of the three major clades, suggests advanced lineage sorting, either due to limited dispersal abilities, glacial isolation in distinct local microrefuges or both acting in accord. The localized distribution of endemic haplotypes in the northern and central plains as well as in the mountainous eastern and southern parts of the distribution range supports the existence of multiple microrefuges there. Records of haplotypes of distinct clades in sympatry or close geographic proximity are likely the result of Holocene range expansions. In recent years, thousands of confiscated steppe tortoises were released into the wild. The detected mitochondrial differentiation offers a powerful tool for nature conservation, as a means of determining the geographic origin of confiscated tortoises and selecting suitable reintroduction regions.

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