Population structure of Nouelia insignis (Asteraceae), an endangered species in southwestern China, based on chloroplast DNA sequences: recent demographic shrinking

Abstract

Nouelia insignis, an endangered species, is distributed in the Jinsha and Nanpan drainage areas in southwestern China. In this study, we examined the genetic diversity and population structure based on the sequences of the cpDNA rpL 16 intron. Low levels of genetic variation were detected within all populations of the endemic species. A gene genealogy of 11 haplotypes recovered two major lineages I and II, with haplotypes H1 and H6 nested as interior nodes, respectively. Haplotype H1 was widespread in all populations, while haplotype H6 was restricted to populations southern of the Jinsha River. Low levels of genetic differentiation were detected, as most F (st) values between populations were zero. This result, however, contradicts previous studies based on allozymes and fingerprinting. Genetic analyses suggested that coancestry due to low evolutionary rates resulted in the lack of geographical subdivision. Molecular dating estimated that the two lineages split about 3.224 MYA (95% CI 1.070-6.089 MYA). Maintenance of ancestral polymorphisms was possibly attributable to a long-standing large effective population size until recently. Postglacial demographic expansion was supported by a unimodal mismatch distribution and star-like phylogenies.

Systematics of the genusSalweenia(Leguminosae) from Southwest China with discovery of a second species

“…Using 3.3 × 10 − 10 and 6.6 × 10 − 10 substitutions per site per year determined for the nodes containing Piptanthus and Sophora in a study of evolutionary rates analysis across the family Leguminosae (Lavin & al., 2005), we estimated that the divergence time of S. wardii and S. bouffordiana was around 3.03-6.06 Ma, which time is grossly congruent with results from studies of freshwater fishes, e.g., 4.4-6.8 Ma for Schizothorax Heckel (He & Chen, 2006), 1.5-8.0 Ma for glyptosternoid catfishes (Peng & al., 2006), as well as results from plant studies, e.g., 0.82-4.39 Ma for Terminalia franchetii (Combretaceae) (Zhang, 2010;Zhang & Sun, 2011), and 3.224 Ma for Nouelia insignis Franch. (Asteraceae) (Gong & al., 2011). In contrast to its relatively recent speciation, Salweenia is thought to be a relict of the Tertiary flora and may have had a Gondwanan origin (Li & Ni, 1982;Wang, 1989;Wu & al., 2003), indicating it had a long evolutionary history before differentiating.…”

Diversity and conservation of plant species in dry valleys, southwest China

“…in Jinsha River and Nanpan River drainage in northern Yunnan and western Sichuan Provinces. Due to its usage as firewood as well as its habitat destruction and fragmentation, most of the extant populations consist of fewer than 80-100 individuals, with total no more than 5000 individuals surviving in the wild (Gong et al 2011;Luan et al 2006).…”

“…2), which include (1) A. glaucifolium (Guan et al 2013), M. delavayi (Jia et al 2014), A. delavayi (Yang et al 2014) and T. gracilis (unpublished) becoming endangered due to the hydropower stations construction, (2) N. insignis (Gong et al 2011;Luan et al 2006), Leucomeris decora (Zhao and Gong 2012) and Cycas hongheensis (only two populations left) (unpublished) with decreasing populations because of human exploitation for woods or habitat destruction, (3) Psammosilene tunicoides facing overexploitation threats for herb medicines (Zhang et al 2011b), and Citrus hongheensis which is also an important wild germplasm resource (Table 1). We attempt to provide insights into genetic diversity and guidance on conservation managements for these species.…”

“…Our research used neutral markers to measure levels of genetic variation in the endemic species distributed in this region. Overall, low levels of genetic diversity within populations (Hs), as examined from cytoplasm DNA (cpDNA and mtDNA), were revealed, especially in the endangered species such as L. decora (only two cpDNA haplotypes) (Zhao and Gong 2012), A. glaucifolium (Guan et al 2013), N. insignis (Gong et al 2011), P. Tunicoides (Zhang et al 2011b). These genetic patterns may be mainly ascribed to the fragmented distribution and limited gene flow among populations.…”

Genetic structure and phylogeography of Pyrus pashia L. (Rosaceae) in Yunnan Province, China, revealed by chloroplast DNA analyses

“…Therefore, range expansion was an important process in forming the current genetic and phylogeographic structure of this species. Some studies have demonstrated that there are several refugia in Yunnan Province (e.g., Gong et al 2011;Wang and Guan 2011). In general, populations in refugia harbor displayed higher level of genetic diversity and private haplotypes than do migratory populations (Avise 2000;Petit et al 2003).…”