Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian, People's Republic of China.
PLoS One. 2020 May 29;15(5):e0233714. doi: 10.1371/journal.pone.0233714. eCollection 2020.
Toll-like receptor (TLR) genes have recently been employed to assess genetic diversity, as they can be used to infer both demographic history and adaptation to environments with different pathogen pressure. Here, we sampled 120 individuals of the Chinese egret (Egretta eulophotes), a globally vulnerable species, from four breeding populations across China. We assessed the levels of genetic diversity, selection pressure, and population differentiation at seven TLR loci (TLR1LB, TLR2A, TLR3, TLR4, TLR5, TLR7, and TLR15). Using a variety of metrics (SNPs, heterozygosity, nucleotides, haplotypes), our analyses showed that genetic diversity was lower at 4 of the 7 TLR loci in the vulnerable Chinese egret compared to the more common little egret (Egretta garzetta). The selection test indicated TLRs, except for TLR5, were under purifying selection in TLR evolution, suggesting that low TLR genetic diversity in the Chinese egret may be caused by purifying selection. Moreover, analysis of molecular variance indicated low but significant population differentiation among four populations at all of the TLR loci in this egret. However, some comparisons based on fixation index analyses did not show significant population differentiation, and Bayesian clustering showed admixture. Our finding suggested that these four populations of the Chinese egret in China may be considered a single unit for conservation planning. These results, the new report of TLR genetic diversity in a long-distance migratory vulnerable Ardeid species, will provide fundamental TLR information for further studies on the conservation genetics of the Chinese egret and other Ardeids.
Toll-like 受体(TLR)基因最近被用于评估遗传多样性,因为它们可以用来推断种群历史和对不同病原体压力环境的适应。在这里,我们从中国的四个繁殖种群中采集了 120 只中国白鹭(Egretta eulophotes)个体,这是一种全球易危物种。我们评估了七个 TLR 基因座(TLR1LB、TLR2A、TLR3、TLR4、TLR5、TLR7 和 TLR15)的遗传多样性、选择压力和种群分化。使用多种指标(SNP、杂合度、核苷酸、单倍型),我们的分析表明,与更为常见的小白鹭(Egretta garzetta)相比,脆弱的中国白鹭在 7 个 TLR 基因座中的 4 个基因座的遗传多样性较低。选择测试表明,TLR 除 TLR5 外,在 TLR 进化中受到净化选择,这表明中国白鹭中 TLR 遗传多样性较低可能是由于净化选择所致。此外,分子方差分析表明,在中国白鹭的所有 TLR 基因座中,四个种群之间存在低但显著的种群分化。然而,基于固定指数分析的一些比较并没有显示出种群分化,贝叶斯聚类显示存在混合。我们的发现表明,中国的这四个中国白鹭种群可能被视为一个单一的保护规划单元。这些结果,即长距离迁徙的脆弱性鹳形目物种 TLR 遗传多样性的新报告,将为进一步研究中国白鹭和其他鹳形目物种的保护遗传学提供基本的 TLR 信息。