Abstract
BackgroundCurrent and historical events have both affected the current distribution patterns and intraspecific divergence of plants. While numerous studies have focused on the Qinghai-Tibetan Plateau (QTP), the impacts of such events on the flora of subtropical China remain poorly understood. Subtropical China is famous for its highly complex topography and the limited impact from glaciation during the Pleistocene; this may have resulted in a different genetic legacy for species in this region compared to fully glaciated areas.Methodology/Principal FindingsWe used plastid and nuclear DNA sequence data and distribution modeling to analyze the divergence patterns and demographic history of Primula obconica Hance, a widespread herbaceous montane species in subtropical China. The phylogenetic analysis revealed two major lineages (lineage A and lineage B), representing a west-east split into the Yunnan and Eastern groups, and the Sichuan and Central groups, respectively. The Eastern and Central groups comprised relatively new derived haplotypes. Nested Clade Analysis and Bayesian Skyline Plot analyses both indicated that P. obconica mainly experienced a gradual expansion of populations. In addition, the simulated distribution of P. obconica during the Last Glacial Maximum was slightly larger than its present-day distribution.Conclusion/SignificanceOur results are the first to identify a west-east migration of P. obconica. The gradual expansion pattern and a larger potential distribution range in cold periods detected for P. obconica indicate that the population expansion of this species is consistent with the phalanx model. In addition, the current patterns of genetic differentiation have persisted as a result of the extensive environmental heterogeneity that exists in subtropical China.
Highlights
The distribution patterns and evolution of plants are profoundly impacted by their life history traits, environmental heterogeneity and historical events
Compared with the pioneer model which has been well documented in Europe and North America, the phalanx model has received comparatively little attention despite its potential importance in the evolution and demographic history of montane species
Twenty-three populations were sampled throughout the distribution range of P. obconica, representing four subspecies (Figure 1, Table 1)
Summary
The distribution patterns and evolution of plants are profoundly impacted by their life history traits, environmental heterogeneity and historical events. The pioneer model, first described by Hewitt [2], predicts that the pioneer (or edge) population expanding from a refugium will have relatively low genetic diversity as a result of founder effects. The phalanx model, first documented for alpine species [3,6,7], describes the effects of slower expansions from refugia, with less significant bottlenecks than those encountered in pioneer-type expansions because many alleles are able to colonize sites over short distances [2]. Subtropical China is famous for its highly complex topography and the limited impact from glaciation during the Pleistocene; this may have resulted in a different genetic legacy for species in this region compared to fully glaciated areas
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