Quaternary climate change and habitat preference shaped the genetic differentiation and phylogeography of sect. in the southern Qinghai-Tibetan Plateau.

There are two long-standing biogeographic hypotheses regarding the glacial survival of plant species in the Qinghai-Tibetan Plateau (QTP): the in situ survival hypothesis and the hypothesis. We tested these two hypotheses in a phylogeographic study of sect. , a monophyletic section with ecologically divergent lineages. Molecular data from the nuclear internal transcribed spacer, six plastid markers and 13 nuclear microsatellite loci were analyzed for 240 individuals from 19 populations of this section. Environmental data were used to analyze the niches of major phylogenetic lineages within this section and to model changes in their distributions since the Last Glacial Maximum (LGM). We found that sect. consists of three evolutionary lineages: all populations of , populations at the southern edge of the QTP, and populations in the interior part of the QTP. During the LGM, the survival of in the interior part of the QTP corresponded with the in situ survival hypothesis, while most probably survived the LGM in a manner corresponding with the hypothesis. The evolutionary history of different lineages of this section was shaped by topography, climate change, and lineage-specific habitat preferences.