PDF(Pubmed)
Abstract：
Endangered species generally have small populations with low genetic diversity and a high genetic load. Thuja sutchuenensis is an endangered conifer endemic to southwestern China. It was once considered extinct in the wild, but in 1999 was rediscovered. However, little is known about its genetic load. We collected 67 individuals from five wild, isolated T. sutchuenensis populations, and used 636,151 SNPs to analyze the level of genetic diversity and genetic load in T. sutchuenensis to delineate the conservation units of T. sutchuenensis, based on whole transcriptome sequencing data, as well as target capture sequencing data. We found that populations of T. sutchuenensis could be divided into three groups. These groups had low levels genetic diversity and were moderately genetically differentiated. Our findings also indicate that T. sutchuenensis suffered two severe bottlenecks around the Last Glaciation Period and Last Glacial Maximum. Among Thuja species, T. sutchuenensis presented the lowest genetic load and hence might have purged deleterious mutations efficiently through purifying selection. However, distribution of fitness effects analysis indicated a high extinction risk for T. sutchuenensis. Multiple lines of evidence identified three management units for T. sutchuenensis. Although T. sutchuenensis possesses a low genetic load, low genetic diversity, suboptimal fitness, and anthropogenic pressures all present an extinction risk for this rare conifer. This might also hold true for many endangered plant species in the mountains all over the world.
摘要：
濒危物种通常具有低遗传多样性和高遗传负荷的小种群。Thujasutchuenensis是中国西南部特有的濒危针叶树。它曾经被认为在野外灭绝，但在1999年被重新发现。然而,对它的遗传负荷知之甚少。我们从五个野外收集了67个个体，孤立的苏川T。种群，并使用636,151个SNP来分析T.sutchuenensis的遗传多样性和遗传负荷水平，以描绘T.sutchuensis的保护单位，基于整个转录组测序数据，以及目标捕获测序数据。我们发现，苏门毛虫的种群可以分为三组。这些群体的遗传多样性水平较低，遗传分化程度中等。我们的发现还表明，在最后一个冰川期和最后一个冰川期之间，T.sutchuenensis遭受了两个严重的瓶颈。在图亚物种中，T.sutchuenensis表现出最低的遗传负荷，因此可能通过纯化选择有效地清除了有害突变。然而,适应性效应的分布分析表明，苏门毛虫的灭绝风险很高。多行证据确定了木川的三个管理单位。尽管木川具有较低的遗传负荷，低遗传多样性，次优适应度，和人为的压力都给这种罕见的针叶树带来了灭绝的风险。这也可能适用于世界各地山区的许多濒危植物物种。
