Abstract
Biogeographic regionalization can help to better understand diversity in biogeography, conservation, and macroecology. Historical regionalization schemes typically focus on species distributions, often rarely considering the rich context that phylogeographic information can provide. We investigated whether phylogeographic data could help to delineate floristic regions in the Qinghai-Tibet Plateau (QTP)-Hengduan Mountains (HDM) region by analyzing phylogeographic structure in the herb Parasyncalathium souliei (Asteraceae). We sequenced the plastid psbA-trnH and trnL-rpl32 spacer regions for 417 individuals in 36 populations across the geographic range of the species. To estimate the phylogeographic history of this species, a series of population genetic, phylogenetic, molecular dating, and haplotype network analyses were conducted, as were tested for historical demographic expansions. Using occurrence data, species distribution modeling was used to estimate geographic distributions at three time points: the present, the Mid-Holocene and the Last Glacial Maximum. Significant phylogeographic structure was evident (NST> GST; P < 0.05) among the 37 haplotypes detected. Four major haplogroups were identified based on phylogenetic analyses. Private haplotypes were restricted to geographically distinct regions that generally corresponded to previously identified biogeographic subregions within the QTP-HDM region. Our results imply Pliocene-Pleistocene diversification of P. souliei and suggest that the species may have been geographically widespread early in its history. This study may provide valuable evidence for phylogeographic regionalization using chloroplast genetic data in a common, widespread endemic species from the QTP-HDM.
Highlights
The Himalayas, especially their core regions, i.e., the QinghaiTibet Plateau (QTP) and the Hengduan Mountains (HDM), comprise one of the key high-altitude biodiversity hotspots in the world (Myers et al, 2000)
Our goals were to explore: (1) how topography/geography and Pleistocene climatic oscillations have shaped the present-day distributions of P. souliei; (2) whether significant divergence and genetic structure exists among P. souliei populations across different floristic regions/subregions; and (3) whether phylogeographic information may be useful in characterizing potential phylogeoregions in the Qinghai-Tibet Plateau (QTP)-HDM region
We propose that the history of individual species, and in particular those that are widely distributed within biodiversity hotspots, may provide key information to help delineate phylogeoregions, such as in the QTP-HDM (Appendix 6)
Summary
The Himalayas, especially their core regions, i.e., the QinghaiTibet Plateau (QTP) and the Hengduan Mountains (HDM), comprise one of the key high-altitude biodiversity hotspots in the world (Myers et al, 2000). In an influential study, Wu and Wu (1996) divided these regions into two floristic subkingdoms, Sino-Himalayan and the Tibetan Plateau, based on the distribution of taxa endemic to these areas (Figure 1A). The former subkingdom includes most parts of the Yunnan Plateau, HDM, and the East Himalayan region, while the latter subkingdom is composed of most regions of the QTP including the Tangut the Tibet–Pamir–Kunlun, and the Western Himalayan region. The results of these studies have rarely been incorporated into analyses of phylogeographic regionalization, in contrast to other areas such as South America (Amarilla et al, 2015)
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