Abstract
Prinsepia Royle (Rosaceae) is a genus native to China and the Himalayan region. In order to explain its current fragmented distribution pattern and to compare the impact of relatively recent climate changes on the genetic structure of Prinsepia species in different regions of China, a total of 66 populations and 617 individuals of four species of Prinsepia were genotyped, using three cpDNA markers. Meanwhile, phylogenetic reconstructions and divergence dating were conducted using the cpDNA haplotypes dataset and the nuclear ribosomal internal transcribed spacer (ITS) dataset, respectively. Ecological niche modeling (ENM) was performed to predict the potential distribution of each species of Prinsepia at present and during the Last Glacial Maximum. Both ITS and cpDNA gene trees support a north-south divergence of Prinsepia species in China. The divergence time of the northern and southern Clades occurred around the late Oligocene epoch. Combining the present distribution of Prinsepia species and their habitats, we inferred that the transition to a monsoon climate system in East Asia during the late Oligocene epoch, created a humid forest vegetation zone from central to East China, which potentially gave rise to the north-south divergence of Prinsepia species. Both regional climates and allopatric divergence may have played an important role in the speciation of P. sinensis and P. uniflora. P. sinensis had the lowest genetic diversity and a putative northward post-glacial colonization. The distribution range of P. uniflora was also extremely sensitive to interglacial-glacial cycles. P. utilis from southwestern China preserved more haplotypes than P. sinensis and P. uniflora due to its multiple and isolated refugia.
Highlights
East Asia harbors the most diverse temperate flora in the world, with a vast number (>600) of endemic genera (Wu and Wu, 1996; Manchester et al, 2009)
Because the reliable fossil of Oemleria has been dated to late in the early Eocene epoch (49.42 ± 0.54 Ma) (Benedict et al, 2011), the origin time for Prinsepia should not follow after this time, if no other group had become extinct
These existing temperate taxa or their ancestors in East Asia or North America had a more northerly distribution in the Paleogene epoch, i.e., Arcto-Tertiary Flora (Milne and Abbott, 2002), so Prinsepia probably diverged from Oemleria in a high or middle-high latitude area and spread southward gradually along the mountain chains of China (Figure 7)
Summary
East Asia harbors the most diverse temperate flora in the world, with a vast number (>600) of endemic genera (Wu and Wu, 1996; Manchester et al, 2009). It has been suggested that before the onset of the EASM, there was a broad belt of subtropical arid and semiarid vegetation, extending from east to northwest China (Guo et al, 2008). The eastern and central parts of this arid and semiarid vegetation zone were replaced by a humid forest vegetation zone with the establishment of the East Asian monsoon system, and the arid and semiarid zone became restricted to northwest China (Guo et al, 2008). Multiple changes to aridity or monsoon intensity have occurred in East Asia since (Sun and Wang, 2005; Wang et al, 2008)
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