Data from: Genetic variation and population structure in the endangered Hermann’s tortoise: the roles of geography and human-mediated processes

The Hermanni’s tortoise (Testudo hermanni) is an endangered land tortoise distributed in disjoint populations across Mediterranean Europe. We investigated its genetic variation by typing one mitochondrial locus and nine nuclear microsatellites in approximately 300 individuals from 22 localities. Our goal was to understand the relative impact of natural and human-mediated processes in shaping the genetic structure, and to identify the genetic priorities for the conservation of this species. We found that i) all geographic areas are highly differentiated, mainly as a function of their distance but with a clear genetic discontinuity (Fst values larger than 0.4) between the Eastern and the Western subspecies; ii) the contact zone between subspecies is located farthest to the west than previously believed, and it probably coincides with the delta of the largest Italian river; iii) extinction events due to climatic conditions in the Upper Palaeolithic and subsequent human-mediated translocations in the Neolithic possibly explain the unexpected similarity among Spain, Sicily and Corsica. For conservation purposes, the large majority of genetic pools appears autochthonous, although hybridization among subspecies, related to extensive 20th century trade of tortoises across Europe, is observed in Spain and some Italian samples. Most populations do not seem at immediate risk of low genetic variation, except the French population, which has very low nuclear genetic diversity (heterozygosity = 0.25) and where 50 out of 51 sampled animals shared the same mitochondrial sequence. In general, restocking and reintroduction plans should carefully consider the genetic background of the individuals.

赫尔曼陆龟（Testudo hermanni）是一种濒危陆龟，其种群呈间断分布于地中海欧洲区域。本研究通过对来自22个采样点的约300个个体进行1个线粒体基因座与9个核微卫星位点的基因分型，解析了该物种的遗传变异情况。本研究的核心目标为厘清自然过程与人为介导过程对其遗传结构形成的相对影响，并确定该物种的保护遗传优先事项。研究结果如下：① 所有地理区域的遗传分化程度均较高，分化水平主要随地理距离增加而升高，但东西两个亚种之间存在显著的遗传间断（Fst值大于0.4）；② 亚种间的接触带位置较此前认知更为偏西，其大概率与意大利境内最大河流的三角洲重合；③ 旧石器时代晚期受气候条件驱动的种群灭绝事件，以及新石器时代后续发生的人为跨区域迁移活动，或可解释西班牙、西西里岛与科西嘉岛之间存在的意外遗传相似性。从物种保护的视角来看，绝大多数遗传基因库均为土著起源，但在西班牙与部分意大利样本中观测到了亚种间的杂交现象，该现象与20世纪欧洲范围内大规模的陆龟贸易活动密切相关。除法国种群外，多数种群暂未出现遗传多样性偏低的直接风险。法国种群的核遗传多样性极低（期望杂合度He=0.25），且51个采样个体中有50个共享同一线粒体序列。总体而言，陆龟的种群补植与再引入计划需充分考量个体的遗传背景。