Phylogeography Of The Genus Dasiphora(Rosaceae) In The Qinghai-Tibetan Plateau

The uplifts of the Qinghai-Tibetan Plateau (QTP) and the Quaternary climatic oscillations are suggested to have caused extensive allopatric divergences that account for this region’s high species diversity. However, range shifts during the inter-geological or interglacial stages may have counteracted such allopatric divergences due to mutual introgressions involving dominant species, which adapted rapidly to changes in the climate and their habitats. We tested this hypothesis by performing a phylogeographic study on the shrub genus Dasiphora (Rosaceae). Two species within this genus can be distinguished based on their petal colors and are widely distributed dominant shrubs on the QTP. We sequenced two chloroplast DNA (cpDNA) fragments (rbcL and trnT-L) and the nuclear ribosomal internal transcribed spacer (ITS) for558individuals from71populations. In total,112cpDNA haplotypes and134ITS genotypes were recovered. All of these haplotypes or genotypes comprised a monophyletic lineage within the expanded samples from this genus and the related ones. The cpDNA haplotypes clustered into three distinct groups with deep divergences, none of which was species-specific. Significant and distinct expansion signals were detected within two of the three cpDNA groups. The divergences between the identified cpDNA haplotype groups and the expansions within these groups were dated to between the Pliocene and the late Pleistocene. Similarly, different and deeply diverged ITS sequence groups were identified; these also did not exhibit complete interspecific delimitation. However, all of the identified cpDNA or ITS groups were geographically correlated to some extent. These results suggest that recent plateau uplifts and climatic oscillations might have caused the deep divergences observed within this genus. However, later range expansions probably blurred these allopatric divergences and species boundaries. Our results highlight the evolutionary complexity of the dominant components of the QTP ecosystems, which arose from rapid range shifts in response to geological and/or climatic oscillations.