Abstract
Narrow-ranged species face challenges from natural disasters and human activities, and to address why species distributes only in a limited region is of great significance. Here we investigated the genetic diversity, gene flow, and genetic differentiation in six wild and three cultivated populations of Thuja sutchuenensis, a species that survive only in the Daba mountain chain, using chloroplast simple sequence repeats (cpSSR) and nuclear restriction site-associated DNA sequencing (nRAD-seq). Wild T. sutchuenensis populations were from a common ancestral population at 203 ka, indicating they reached the Daba mountain chain before the start of population contraction at the Last Interglacial (LIG, ∼120–140 ka). T. sutchuenensis populations showed relatively high chloroplast but low nuclear genetic diversity. The genetic differentiation of nRAD-seq in any pairwise comparisons were low, while the cpSSR genetic differentiation values varied with pairwise comparisons of populations. High gene flow and low genetic differentiation resulted in a weak isolation-by-distance effect. The genetic diversity and differentiation of T. sutchuenensis explained its survival in the Daba mountain chain, while its narrow ecological niche from the relatively isolated and unique environment in the “refugia” limited its distribution.
Highlights
In the context of biodiversity loss worldwide, it is critical to conserve endangered species that are generally narrow ranged (Chau et al, 2013)
We assessed the wild populations of T. sutchuenensis using chloroplast simple sequence repeats and nuclear restriction site-associated DNA sequencing and found relatively high chloroplast genetic diversity but low nuclear genetic diversity, which provides molecular explanation in its distribution in the Daba mountains as a “refugia”
T. sutchuenensis was widely distributed in China in the late Pliocene based on its fossil in the Shanxi province (Figure 1C) (Cui et al, 2015), and its distributed area and population size decreased from the Last Interglacial (LIG, ∼120–140 ka) to the Last Glacial Maximum (LGM, ∼22 ka) (Qin et al, 2017)
Summary
In the context of biodiversity loss worldwide, it is critical to conserve endangered species that are generally narrow ranged (Chau et al, 2013). The plant species with extremely small populations (PSESP) is proposed as a conservation concept to protect them (Yang et al, 2020) These species face extinction risk at any time because their population size is below a stable survival limit and suffers long-term interference and stress from external factors (Yang et al, 2020). The population demographic history is generally influenced by tectonic events and climatic change that, are key factors influencing patterns of genetic diversity (Sun et al, 2015) These tectonic and climatic events cause contraction–expansion of effective population size, thereby forming the current genetic structure (Bai et al, 2018). Previous studies showed inconsistent results for T. sutchuenensis populations from different methods, high genetic diversity with ISSR (Liu et al, 2013), and low genetic diversity with six singlecopy nuclear loci (Qin et al, 2020)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
