Molecular data and ecological niche modelling reveal the phylogeographic pattern of the widespread shrub Tamarix chinens
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ISSN: 0075-5974 (print) ISSN: 1874-933X (electronic)
Molecular data and ecological niche modelling reveal the phylogeographic pattern of the widespread shrub Tamarix chinensis Lour. (Tamaricaceae) in China Likun Sun1, Guangxiu Liu2, Yongli Lu3, Baogui Zhang4 & Gaoseng Zhang2
Summary. Tamarix chinensis Lour. is a perennial shrub that is highly adapted to flooded and salty conditions with a
wide distribution. In this paper, a phylogeographic history of T. chinensis including 20 populations from China was inferred using two chloroplast DNA (cpDNA) segments (trnL-trnF, and rps16) and one nuclear ribosomal DNA (nrDNA) region. A total of 11 ribotypes and 16 chlorotypes were identified. The total nucleotide diversity (HT) of the nrITS and cpDNA were 0.803 and 0.635 respectively, showing a moderate level of genetic variation. The haplotype trees of both nrITS and cpDNA exhibited an H1-centred radiation differentiation pattern. In addition, both cpDNA and nrITS data showed no significant population differentiation within T. chinensis. AMOVA results revealed that almost all genetic variations existed within the populations. Furthermore, we found relatively stronger population differentiation based on nrITS rather than that of cpDNA. nrITS indicated a significant positive correlation between the genetic differentiation coefficient and geographic distance. These results implied that seed dispersal is more efficient than pollen dispersal in T. chinensis. The molecular data and ecological niche modelling also indicated that T. chinensis retreated into refugia on a large-scale during the Last Glacial Maximum (LGM) period and then there was sudden population expansion and recolonisation of suitable habitats after the glacial period. Key Words. cpDNA, ecological niche model, nrDNA, phylogeography.
Introduction Profound climatic oscillations during the Quaternary glacial period and subsequent periodic fluctuations resulted in repeated acute environmental changes, which also substantially shaped species distribution, evolution, and extinction (Comes & Kadereit 1998; Hewitt 2000, 2004). Many plant species sought refuge during the Pleistocene Epoch (Petit et al. 2003). The distributions of these glacial refugia, the potential recolonisation routes, and the subsequent evolution and speciation of plants during glacial and post-glacial epochs has been extensively studied for Europe, East Asia, North America and the Qinghai-Tibetan plateau (Horsak et al. 2019; Muellner-Riehl 2019; Park & Donoghue 2019; Song et al. 2018; Xia et al. 2018). China’s warm-temperate zone generally refers to the area between 32°30' – 42°30' and 103°30' – 124°10', which comprises an area of approximately 7 × 105 km2 (Shangguan et al. 2009). The typical vegetation in this region is deciduous broadleaved forest (Gao et al. 2001). This warm temperate zone
had not been strongly influenced by massive Quaternary glaciers since the Tertiary Period. So unlike the large-scale extinction of broadleaved species in Europe and North America, the majority of species among the vege
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