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）是一类濒危陆龟，其种群呈碎片化分布于地中海欧洲区域。本研究对采自22个样点的约300个个体开展基因分型，检测了1个线粒体位点（mitochondrial locus）与9个核微卫星位点（nuclear microsatellites），以此解析该物种的遗传变异特征。本研究旨在明确自然过程与人为介导过程对该物种种群遗传结构塑造的相对影响，并确定该物种保护的遗传优先方向。
研究结果如下：① 所有地理种群均呈现高度遗传分化，分化程度主要随地理距离递增而升高，且东西两个亚种间存在显著遗传间断（遗传分化系数Fst值大于0.4）；② 亚种间的杂交带位置较此前认知更偏西，且大概率与意大利最大河流的河口区域重合；③ 西班牙、西西里岛与科西嘉岛种群间出现的反常遗传相似性，或可通过旧石器时代晚期受气候驱动的种群灭绝事件，以及新石器时代的人为种群移殖活动加以解释。
从保护实践视角来看，绝大多数遗传基因库均为本土起源，但在西班牙与部分意大利样本中，观测到因20世纪欧洲范围内大规模陆龟贸易引发的亚种间杂交事件。多数种群暂未出现遗传多样性快速降低的即时风险，但法国种群除外：该种群的核遗传多样性极低（杂合度heterozygosity=0.25），且51个采样个体中有50个共享同一条线粒体序列。总体而言，陆龟的种群补植与再引入计划需审慎考量个体的遗传背景。