Abstract
BackgroundThe Qinghai-Tibetan Plateau (QTP) and its southern and southeastern mountain ranges, Himalaya-Hengduan Mountains (HHM), are one of the most extensive habitats for alpine plants in the world. How ferns occurring in QTP and HHM changed their distribution ranges in response to Quaternary climatic oscillations remains almost unknown.Methodology and ResultsWe employed sequences of two chloroplast DNA regions, rps4-trnS and trnL-trnF, to reconstruct phylogeography of the Sino-Himalayan fern Lepisorus clathratus, occurring mainly in the QTP and HHM. Individuals of this species have either dehiscent or indehiscent sporangia with the latter evolved from the plesiomorphic dehiscent forms. Based on a range-wide sampling, we detected 27 cpDNA haplotypes that were divided into five groups by network analyses. Populations in the Hengduan Mountains possess the highest genetic diversity, while a single haplogroup is detected across the north-central region. A distinct phylogeographical subdivision was detected between the Hengduan Mountains and north-central region by AMOVA analysis. The haplogroup distribution pattern, coalescence and AMOVA analysis suggest that a long term survival area (refugia) of the species was located in the Hengduan Mountains during glaciations, with probable range expansions into north-central regions during interglacial periods. Populations with indehiscent sporangium can carry private haplotypes and are inclined to maintain genetic homogeneity. One group with indehiscent sporangia most likely survived in situ on the QTP during glaciations.Conclusions/SignificanceThis study for the first time sheds light on the response of alpine ferns in the QTP and HHM to the Quaternary climatic oscillations.
Highlights
The Himalaya-Hengduan Mountains region (HMM) is home to over 20,000 species of vascular plants and harbors the richest alpine flora on earth, with notable richness of endemic species [1,2]
The region extends along the southern frontier to the southeastern rim of the Qinghai-Tibetan Plateau (QTP), which comprises an area of approximately 2.56106 km2 with average altitudes of ca. 4,000 m
The vegetation in the QTP and Himalaya-Hengduan Mountains (HHM) is regarded as highly sensitive and vulnerable to climate change [5]. This vulnerability may be reflected in the genetic pattern of extant populations/species occurring in this region because climatic oscillation of the Pleistocene has likely shaped the spatial distribution of genetic diversity [6]
Summary
The Himalaya-Hengduan Mountains region (HMM) is home to over 20,000 species of vascular plants and harbors the richest alpine flora on earth, with notable richness of endemic species [1,2]. Our knowledge of phylogeographical histories of organisms occurring in the QTP and HHM as well as causal correlations with climatic fluctuations has been limited so far, due to finite phylogeographical studies in the QTP and its adjacent areas in particular for plants [8,9,10,11,12,13,14,15,16,17,18] These studies suggest remarkable differences in the phylogeographical history of the species involved, two main patterns might be inferred. How ferns occurring in QTP and HHM changed their distribution ranges in response to Quaternary climatic oscillations remains almost unknown
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