High variation and strong phylogeographic pattern among cpDNA haplotypes in Taxus wallichiana (Taxaceae) in China and North Vietnam

Abstract

We studied the phylogeography of Chinese yew (Taxus wallichiana), a tree species distributed over most of southern China and adjacent regions. A total of 1235 individuals from 50 populations from China and North Vietnam were analysed for chloroplast DNA variation using polymerase chain reaction-restriction fragment length polymorphism of the trnL-F intron-spacer region. A total of 19 different haplotypes were distinguished. We found a very high level of population differentiation and a strong phylogeographic pattern, suggesting low levels of recurrent gene flow among populations. Haplotype differentiation was most marked along the boundary between the Sino-Himalayan and Sino-Japanese Forest floristic subkingdoms, with only one haplotype being shared among these two subkingdoms. The Malesian and Sino-Himalayan Forest subkingdoms had five and 10 haplotypes, respectively, while the relatively large Sino-Japanese Forest subkingdom had only eight. The strong geography-haplotype correlation persisted at the regional floristic level, with most regions possessing a unique set of haplotypes, except for the central China region. Strong landscape effects were observed in the Hengduan and Dabashan mountains, where steep mountains and valleys might have been natural dispersal barriers. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggest the existence of several localized refugia during the last glaciation from which the present-day distribution may be derived. The pattern of haplotype distribution across China and North Vietnam corresponded well with the current taxonomic delineation of the three intraspecific varieties of T. wallichiana.

Long‐distance dispersal or postglacial contraction? Insights into disjunction between Himalaya–Hengduan Mountains and Taiwan in a cold‐adapted herbaceous genus, Triplostegia

“…3.31 Ma, Taiwania cryptomerioides , Chou, Thomas, Ge, LePage, & Wang, 2011; c . 3.29 Ma, Taxus wallichiana , Gao et al., 2007) was congruently inferred to be mid‐Pliocene, which was shortly after Taiwan attained its modern form. The lowest differentiation index between CC and TW (Tables S5 and S6) and the more similar leaf blades (Figure 4) further support the idea that TW populations are descendants of CC.…”

“…TW populations are all from the central mountain range of Taiwan (average elevation: 2,321 m) and possess five cpDNA and six ITS haplotypes. Strong geography‐haplotype‐correlated genetic structures were also detected in birds (Qu et al., 2015; Wang et al., 2013), insects (Ye et al., 2014), and plants (Gao et al., 2007; Meng et al., 2017), which highlight the importance of topographic complexity in promoting species differentiation both by increasing habitat diversity and limiting gene flow between elevation‐restricted populations (Hoorn, Mosbrugger, Mulch, & Antonelli, 2013; Verboom, Bergh, Haiden, Hoffmann, & Britton, 2015). …”

Morphological and molecular data from Madeira support the persistence of an ancient lineage ofTaxus baccataL. in Macaronesia and call for immediate conservation actions

“…The phylogenetic analyses resulted from ITS may suggest the persistence of an early lineage of Eurasian Taxus in Macaronesia resolved as paraphyletic with respect to the continental accessions, while the cpDNA tree showed a reciprocal monophyly of Macaronesian and Afro-European populations, stressing the hypothesis of a separate evolutionary line within T. baccata. This incongruence in the tree patterns may be explained by the different mutation rate of the two markers (Wolfe et al 1987;Gao et al 2007), convergent evolution, lineage sorting, or hybridization and introgression (Simeone et al 2009;Acosta and Premoli 2010). Although more extensive samplings across the entire yew range would certainly be required, shared polymorphisms might speak in favour of ancestry for both lineages, suggesting a closer derivation to the yew ancestral line than those examined from Mediterranean and European regions.…”

Significance of pre-Quaternary climate change for montane species diversity: Insights from Asian salamanders (Salamandridae: Pachytriton)

“…Among those mountains, Huangshan (site 18), the type locality of P. feii, is located at the lower reaches of the Yangtze River, a region that has been proposed as a Pleistocene refugium for eastern Asian conifers, frogs and non-migratory birds based on patterns of intraspecific genetic variation (Gao et al, 2007;Zhang et al, 2008a;Li et al, 2009). Huangshan is characterized by a heterogeneous topography with numerous high peaks interspersed among low valleys, where refugia may have been abundant and supported habitats with relatively stable microclimates when the global climate underwent major changes (Qian and Ricklefs, 2000;Li et al, 2009;Song et al, 2009).…”