Abstract
BackgroundDespite its high number of endemic deciduous broad-leaved species in China’s warm-temperate zone, far less attention has been paid to phylogeographic studies in this region. In this work, the phylogeographic history of Forsythia suspensa endemic to China’s warm-temperate zone was investigated to explore the effect of climate change during the Pleistocene on the distribution of this deciduous broad-leaved species in China.ResultsThe cpDNA data revealed seven phylogeographical groups corresponding to geographical regions. By contrast, the nrDNA data supported the samples clustered into three groups, which was inconsistent with separate geographical regions supported by cpDNA data. Ecological niche modeling showed that the climatically suitable area during the cold period was larger than that during the warm period.ConclusionsBoth molecular data and ecological niche modeling indicated that F. suspensa expanded to nearby low-elevation plains in the glacial periods, and retreated to mountaintops during interglacial warmer stages. This study thus supported that F. suspensa persisted in situ during the glacial of the Pleistocene with enlarged distribution area, contrary to the hypothesis of long distance southward migration or large-scale range contraction.
Highlights
Despite its high number of endemic deciduous broad-leaved species in China’s warm-temperate zone, far less attention has been paid to phylogeographic studies in this region
The third hypothesis is that some species were slightly affected by Pleistocene glacial cycles that persisted in situ throughout the Last Glacial Maximum (LGM) and occupied multiple localized glacial refugia, as suggested by some phylogeographical studies in this region on species such as Taxus wallichiana [15], Cathaya argyrophylla [16], and Eurycorymbus cavaleriei [17]
Results chloroplast DNA (cpDNA) diversity and population structure Out of the two cpDNA regions sequenced in F. suspensa (182 individuals, 20 populations), the two regions both showed length variation
Summary
Despite its high number of endemic deciduous broad-leaved species in China’s warm-temperate zone, far less attention has been paid to phylogeographic studies in this region. The second hypothesis is that climatic changes during Pleistocene had a large influence on the forests in China; no large-scale vegetation experienced long-distance southward migration during glaciation and instead contracted into a few main refugia, as suggested by most phylogeographical studies in China [13,14]. Some species reportedly occupied a much larger area than today, e.g., Alsophila spinulosa [18], Pinus kwangtungensis [19], and Primula obconica [20] These studies have mainly focused on the plant species in the regions with high biodiversity, such as Qinghai–Tibetan Plateau, the Himalaya–Hengduan Mountains, and subtropical China, and only a few studies are about China’s warm-temperate zone. More comprehensive studies on species with wide distribution ranges in China’s warmtemperate zone are needed to test the impact on this region during the Pleistocene glacial cycle
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