Genetic Diversity and Population Divergence of a Rare, Endemic Grass (Elymus breviaristatus) in the Southeastern Qinghai-Tibetan Plateau

Abstract

Elymus breviaristatus is a grass species only distributed in the southeast of Qinghai-Tibetan Plateau (QTP), which has suffered from serious habitat fragmentation. Therefore, understanding patterns of genetic diversity within and among natural E. breviaristatus populations could provide insight for future conservation strategies. In this study, sequence-related amplified polymorphism markers were employed to investigate the genetic diversity and hierarchical structure of seven E. breviaristatus populations from QTP, China. Multiple measures of genetic diversity indicated that there is low to moderate genetic variation within E. breviaristatus populations, consistent with its presumed mating system. In spite of its rarity, E. breviaristatus presented high genetic diversity that was equivalent to or even higher than that of widespread species. Bayesian clustering approaches, along with clustering analysis and principal coordinate analysis partitioned the studied populations of E. breviaristatus into five genetic clusters. Differentiation coefficients (Fst, GST, etc.) and AMOVA analysis revealed considerable genetic divergence among different populations. BARRIER analyses indicated that there were two potential barriers to gene flow among the E. breviaristatus populations. Despite these patterns of differentiation, genetic distances between populations were independent of geographic distances (r = 0.2197, p = 0.2534), indicating little isolation by distance. Moreover, despite detecting a common outlier by two methods, bioclimatic factors (altitude, annual mean temperature, and annual mean precipitation) were not related to diversity parameters, indicating little evidence for isolation caused by the environment. These patterns of diversity within and between populations are used to propose a conservation strategy for E. breviaristatus.

Drivers of population divergence and genetic variation in Elymus breviaristatus (Keng) Keng f. (Poaceae: Triticeae), an endemic perennial herb of the Qinghai-Tibet Plateau

“…We extend a previous study ofE. breviaristatus (Yu et al, 2019), which revealed no significant population-level IBD and ignored the environmental features of habitats, by testing for evidence of IBD and IBE in the patterns of genetic variation. We aimed to determine (a) the level, pattern, and structure of genetic variation among and within E. breviaristatuspopulations across the Tibet and Hengduan Mountains transition zone, (b) the possible climatic factors affecting population genetic diversity, and (c) whether the IBD or IBE model best explained the patterns of genetic differentiation among E. breviaristatus populations.…”

“…As many rare species are restricted to the QTP, it is valuable to compare the genetic diversity of these species with that of more widespread congenerics (Wang et al, 2019b). In a previous study, SSR and SRAP markers were used to explore the genetic diversity of seven populations of E. breviaristatus on the Northwest Sichuan Plateau (Gu et al, 2015, Yu et al, 2019. Here, our analyses of EST-SSR data showed that E. breviaristatuspopulations in the transition zone between Tibet and the Hengduan Mountains had lower genetic diversity than congenerics such as E. sibiricus (Ma et al, 2012), E. nutans (Chen et al, 2009, Chen et al, 2013, and E. trachycaulus (Gaudett et al, 2005).…”

“…In 1999, this plant was listed as an important wild plant for conservation in China. Previous investigations have shown that E. breviaristatus has a moderate level of genetic diversity (Gu et al, 2015, Yu et al, 2019. Although genetic diversity determines the ability of species to adapt to the environment, it is challenging to understand the potential mechanisms that have resulted in species scarcity based on genetic diversity alone.…”

Temperature-Mediated Plasticity Regulates the Adaptation of Phytophthora infestans to Azoxystrobin Fungicide

“…The different evolutionary history among geographic populations of P. infestans was supported by the non-association between gene diversity in SSR markers and variances in azoxystrobin resistance ( Figure 6), which is expected to be positively corrected for neutral traits [59]. Furthermore, genetic variation is the main determinant of adaptive ability of species to environments [66], and analysis of genetic variation in species can help us to understand its potential and mechanism of evolutionary adaptation [67]. Our results showed that phenotypic plasticity accounted for~40% of the total phenotypic variation while on average the genetic variation (heritability) accounted for 16% of the variation (Table 1).…”

Why Self-fertilizing Plants Still Exist in Wild Populations: Diversity Assurance through Stress-Induced Male Sterility May Promote Selective Outcrossing and Recombination

“…Although these are wild selfing populations, studies have shown that within-population genetic diversity can be moderate and significant in some of them, and as such they are heterogeneous populations of near-homozygous individual plants. This has been documented in diverse wild populations of grasses, including wild oats in China and the USA [60], Elymus breviaristatus in China [61], Elymus nutans and Elymus sibiricus, important perennial forages, in China [62], Elymus tangutorum, a pasture bunchgrass, in China [63], wild emmer wheat (Triticum turgidum ssp. dicoccoides) in Israel [64], Thinopyrum junceum and Thinopyrum junceiforme in Spain [65], Paspalum dilatatum subsp.…”