Molecular phylogeography and population genetic structure of O. longilobus and O. taihangensis (Opisthopappus) on the Taihang mountains

Abstract

Historic events such as the uplift of mountains and climatic oscillations in the Quaternary periods greatly affected the evolution and modern distribution of the flora. We sequenced the trnL-trnF, ndhJ-trnL and ITS from populations throughout the known distributions of O. longilobus and O. taihangensis to understand the evolutionary history and the divergence related to the past shifts of habitats in the Taihang Mountains regions. The results showed high genetic diversity and pronounced genetic differentiation among the populations of the two species with a significant phylogeographical pattern (NST>GST, P<0.05), which imply restricted gene flow among the populations and significant geographical or environmental isolation. Ten chloroplast DNA (cpDNA) and eighteen nucleus ribosome DNA (nrDNA) haplotypes were identified and clustered into two lineages. Two corresponding refuge areas were revealed across the entire distribution ranges of O. longilobus and at least three refuge areas for O. taihangensis. O. longilobus underwent an evolutionary historical process of long-distance dispersal and colonization, whereas O. taihangensis underwent a population expansion before the main uplift of Taihang Mountains. The differentiation time between O. longilobus and O. taihangensis is estimated to have occurred at the early Pleistocene. Physiographic complexity and paleovegetation transition of Taihang Mountains mainly shaped the specific formation and effected the present distribution of these two species. The results therefore support the inference that Quaternary refugial isolation promoted allopatric speciation in Taihang Mountains. This may help to explain the existence of high diversity and endemism of plant species in central/northern China.

Figure 1. Map of sample sites for Opisthopappus (Asteraceae) on the Taihang Mountains.

Location details are given in Table 1, and locality numbers correspond to those in Table 1. Yellow circle dots represent the populations of O. longilobus; red circle dots represent the populations of O. taihangensis.

Figure 2. Geographical distribution of 10 cpDNA (A) and 18 (B) nrDNA haplotypes.

The pie charts reflect the frequency of haplotype occurrence in each population. Haplotype colours correspond to those shown in panel.

Figure 3. The evolutionary relationships among cpDNA haplotypes.

(A) NJ phylogenetic tree for the 10 cpDNA haplotypes. Numbers above branches are support values from bootstrap resampling/Bayesian inference. (B) Median-joining network. Sizes of the circles are proportional to the overall frequency of the haplotypes in the entire sample of all species.

Figure 4. The evolutionary relationships among nrDNA haplotypes.

(A) NJ phylogenetic tree for the 18 nrDNA haplotypes. Numbers above branches are support values from bootstrap resampling. (B) Median-joining network. Sizes of the circles are proportional to the overall frequency of the haplotypes in the entire sample of all species.