Valbuena-Ureña E, Soler-Membrives A, Steinfartz S, Orozco-terWengel P, Carranza S
Unitat de Zoologia, Facultat de Biociències, Universitat Autònoma de Barcelona, Cerdanyola del Vallès (Barcelona), Spain.
Centre de Fauna Salvatge de Torreferrussa (Catalan Wildlife Service - Forestal Catalana), Finca de Torreferrusa, Barcelona, Spain.
Heredity (Edinb). 2017 May;118(5):424-435. doi: 10.1038/hdy.2016.123. Epub 2017 Jan 11.
Endemic species with restricted geographic ranges potentially suffer the highest risk of extinction. If these species are further fragmented into genetically isolated subpopulations, the risk of extinction is elevated. Habitat fragmentation is generally considered to have negative effects on species survival, despite some evidence for neutral or even positive effects. Typically, non-negative effects are ignored by conservation biology. The Montseny brook newt (Calotriton arnoldi) has one of the smallest distribution ranges of any European amphibian (8 km) and is considered critically endangered by the International Union for Conservation of Nature. Here we apply molecular markers to analyze its population structure and find that habitat fragmentation owing to a natural barrier has resulted in strong genetic division of populations into two sectors, with no detectable migration between sites. Although effective population size estimates suggest low values for all populations, we found low levels of inbreeding and relatedness between individuals within populations. Moreover, C. arnoldi displays similar levels of genetic diversity to its sister species Calotriton asper, from which it separated around 1.5 million years ago and which has a much larger distribution range. Our extensive study shows that natural habitat fragmentation does not result in negative genetic effects, such as the loss of genetic diversity and inbreeding on an evolutionary timescale. We hypothesize that species in such conditions may evolve strategies (for example, special mating preferences) to mitigate the effects of small population sizes. However, it should be stressed that the influence of natural habitat fragmentation on an evolutionary timescale should not be conflated with anthropogenic habitat loss or degradation when considering conservation strategies.
地理分布范围有限的特有物种面临着最高的灭绝风险。如果这些物种进一步分裂为基因隔离的亚种群，灭绝风险就会增加。尽管有一些证据表明栖息地破碎化具有中性甚至积极影响，但通常认为其对物种生存具有负面影响。在保护生物学中，非负面影响通常被忽视。蒙特塞尼溪蝾螈（Calotriton arnoldi）是欧洲两栖动物中分布范围最小的物种之一（8公里），被国际自然保护联盟列为极度濒危物种。在这里，我们应用分子标记分析其种群结构，发现由于自然屏障导致的栖息地破碎化已使种群在基因上强烈分化为两个部分，不同地点之间没有可检测到的迁移。尽管有效种群大小估计表明所有种群的值都很低，但我们发现种群内个体之间的近亲繁殖和亲缘关系水平较低。此外，阿诺德溪蝾螈与其姐妹物种粗糙溪蝾螈（Calotriton asper）的遗传多样性水平相似，大约在150万年前它们从粗糙溪蝾螈分化出来，后者的分布范围要大得多。我们的广泛研究表明，在进化时间尺度上，自然栖息地破碎化不会导致负面的遗传效应，如遗传多样性丧失和近亲繁殖。我们假设处于这种情况下的物种可能会进化出策略（例如特殊的交配偏好）来减轻小种群规模的影响。然而，应该强调的是，在考虑保护策略时，自然栖息地破碎化在进化时间尺度上的影响不应与人为造成的栖息地丧失或退化混为一谈。
