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Santos, A.d.S.
Hist¢ria evolutiva de _Leopardus colocolo_: an lise de padräes filogeogr ficos e sua influˆncia no processo de hibrida‡Æo com _Leopardus tigrinus_
2012  Full Book

The presence of phenotypic differences among geographic populations of the pampas cat, _Leopardus colocolo_, has raised questions about the demographic history and taxonomy of this felid. More recently, initial phylogeographic studies showed that this species indeed possesses a strong genetic structure, but were mostly restricted to Andean samples, so that much of its distribution was not analyzed in detail. Furthermore, the recent discovery of evidence of hybridization between _L. colocolo _and another Neotropical felid (_L. tigrinus_) in central and northeastern Brazil, added an even greater complexity to the evolutionary history of this species. Previous studies have indicated that this hybridization event is relatively old, and is currently detected only as an introgression of _L. colocolo _mitochondrial DNA (mtDNA) into _L. tigrinus _populations, without any trace so far identified in the nuclear genome. Therefore, the aim of this study was to analyze four mitochondrial segments in _L. colocolo _individuals sampled broadly across their geographic distribution, along with samples of _L. tigrinus _hybrids from central and northeastern Brazil. The analysis of 2,141 base pairs of the mtDNA control region and _ATP8_, _ND5 _and _Cyt-b _genes revealed a strong population structure in _L. colocolo_, with high haplotype and nucleotide diversity in comparison with other Neotropical cats. Haplotypes from Chile, Bolivia and Argentina were positioned as the most basal in the phylogeographic structure of _L. colocolo_, while samples from Brazil and Uruguay formed recent, internal groups, suggesting a west-to-east colonization for this species. Demographic analyses indicated the occurrence of two episodes of population expansion, an earlier one (ca. 200,000 years ago) in the west, and another ca. 50,000 years ago in the east. The latter coincides with paleoclimatic and paleogeographic studies that indicated an expansion of grasslands in Brazil and consequent loss of forests. The joint analysis with the _L. tigrinus _hybrid samples revealed a complex history of hybridization. We found no haplotype sharing between _L. colocolo _and _L. tigrinus _hybrids, supporting the hypothesis that this hybridization event is quite old. Moreover, the analysis of population structure revealed that the pampas cat populations from southern Brazil and Uruguay are phylogenetically closer to _L. tigrinus _hybrid haplotypes than to the extant lineages of _L. colocolo _from central and northeastern Brazil. The most plausible interpretation to this unusual pattern is that ancestral _L. colocolo _haplotype lineages from central Brazil have only been sampled in present-day hybrids, and may be extinct in their original species. The observed pattern also indicates that southern Brazil and Uruguay were colonized by _L. colocolo _from central Brazil, with no immediate connection to nearby populations still present in Argentina. This has direct consequences for the conservation of this group, which is geographically isolated and appears to evolve without gene flow (at least mitochondrial) with nearby populations. From an evolutionary standpoint, our results showed the importance of analyzing _L. colocolo _populations from eastern South America, as well as the inclusion of _L. tigrinus _hybrids, because an essential portion of the pampas cat mitochondrial history seems to be currently recorded only by these introgressed haplotypes.

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