Abstract
Climatic fluctuations during the Quaternary significantly affect many species in their intraspecific divergence and population structure across northwest China. In order to investigate the impact of climate change on herbaceous plants, we studied Panzerina lanata (Lamiaceae), a widely distributed species. Sequences of two chloroplast DNA (cpDNA) intergenic spacers (trnH-psbA and rpoB-trnC) and a nuclear ribosomal region (nrDNA, ITS) were generated from 27 populations of Panzerina lanata and resulted in the identification of seven chloroplast haplotypes and thirty-two nuclear haplotypes. We applied AMOVA, neutrality test and mismatch distribution analysis to estimate genetic differentiation and demographic characteristics. The divergence times of the seven cpDNA haplotypes were estimated using BEAST. Our results revealed high levels of genetic diversity (cpDNA: Hcp = 0.6691, HT = 0.673; nrDNA: Hnr = 0.5668, HT = 0.577). High level of genetic differentiation (GST = 0.950) among populations was observed in the cpDNA sequences, while the genetic differentiation values (GST = 0.348) were low in nuclear sequences. AMOVA results revealed major genetic variation among the three groups: northern, central, and eastern group. However, the genetic differentiation in ITS data was not found. The species distribution modeling and demographic analysis indicated that P. lanata had not experienced recent range expansion. The occurrence of divergence between seven cpDNA haplotypes, probably during Pleistocene, coincides with aridification and expansion of the desert across northwest China that resulted in species diversification and habitat fragmentation. In addition, we discovered that the deserts and the Helan Mountains acted as effective geographic barriers that promoting the intraspecific diversity of P. lanata.
Highlights
In China, studies on plant phylogeography have been mainly focusing on four regions: Qinghai-Tibet Plateau and Southwest China, West China, North and Northeast China, South and Southeast China (Liu et al, 2012; Qiu, Fu & Comes, 2011)
Climate change during the Pleistocene led to the low temperatures and aridification in northwest China, which promoted the desert expansion
We identified seven haplotypes (H1–H7) (Table 1) and 17 polymorphic sites (14 substitutions and three indels) from 269 individuals collected from 27 populations (Table 2)
Summary
In China, studies on plant phylogeography have been mainly focusing on four regions: Qinghai-Tibet Plateau and Southwest China, West China, North and Northeast China, South and Southeast China (Liu et al, 2012; Qiu, Fu & Comes, 2011). Geographical barriers (deserts, mountains, etc.) have resulted in segregation of species, limited seeds dispersal, and rare genetic communication between populations, which lead to isolation and differentiation of genetic lineages of species (Cun & Wang, 2010; Liu et al, 2012; Wang et al, 2016) Research in these regions mainly concentrated on shrubs rather than herbaceous plants (Shi & Zhang, 2015; Su, Lu & Zhang, 2016; Su et al, 2015; Xu & Zhang, 2015a) that are more sensitive to climate oscillation. We selected Panzerina lanata (Lamiaceae) as a suitable model to study the genetic structure of desert species in arid northwest China and its response to Quaternary climatic fluctuations
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