Naturalis Biodiversity Center, Leiden, The Netherlands.
Sci Rep. 2020 Feb 3;10(1):1700. doi: 10.1038/s41598-020-58551-0.
Adaptation to different ecological environments can, through divergent selection, generate phenotypic and genetic differences between populations, and eventually give rise to new species. The fire salamander (Salamandra salamandra) has been proposed to represent an early stage of ecological speciation, driven by differential habitat adaptation through the deposition and development of larvae in streams versus ponds in the Kottenforst near Bonn (Germany). We set out to test this hypothesis of ecological speciation in an area different from the one where it was raised and we took the opportunity to explore for drivers of genetic differentiation at a landscape scale. A survey over 640 localities demonstrated the species' presence in ponds and streams across forests, hilly terrain and areas with hedgerows ('bocage'). Genetic variation at 14 microsatellite loci across 41 localities in and around two small deciduous forests showed that salamander effective population sizes were higher in forests than in the bocage, with panmixia in the forests (F < 0.010) versus genetic drift or founder effects in several of the small and more or less isolated bocage populations (F > 0.025). The system fits the 'mainland-island' metapopulation model rather than indicating adaptive genetic divergence in pond versus stream larval habitats. A reanalysis of the Kottenforst data indicated that microsatellite genetic variation fitted a geographical rather than an environmental axis, with a sharp transition from a western pond-breeding to an eastern, more frequently stream-breeding group of populations. A parallel changeover in mitochondrial DNA exists but remains to be well documented. The data support the existence of a hybrid zone following secondary contact of differentiated lineages, more so than speciation in situ.
适应不同的生态环境可以通过分歧选择在种群之间产生表型和遗传差异，并最终产生新的物种。火蝾螈（Salamandra salamandra）被认为代表了生态物种形成的早期阶段，其原因是幼虫在德国波恩附近的科滕福斯特（Kottenforst）溪流与池塘之间的栖息地适应存在差异。我们着手在与提出该假说的地点不同的地区检验这一生态物种形成假说，并借此机会在景观尺度上探索遗传分化的驱动因素。对 640 多个地点的调查表明，该物种存在于池塘和溪流中，这些池塘和溪流分布在森林、丘陵地形和带有树篱（ bocage ）的地区。在两个小的落叶林及其周围的 41 个地点，通过 14 个微卫星基因座的 41 个地点，在 14 个微卫星基因座上的遗传变异显示，在森林中，蝾螈有效种群规模高于 bocage ，森林中存在泛群集（F < 0.010），而在一些较小且或多或少孤立的 bocage 种群中则存在遗传漂变或奠基者效应（F > 0.025）。该系统符合“大陆-岛屿”复合种群模型，而不是指示池塘与溪流幼虫栖息地的适应性遗传分化。对科滕福斯特数据的重新分析表明，微卫星遗传变异与地理而不是环境轴相适应，在西部以池塘繁殖为主的种群与东部以溪流繁殖为主的种群之间存在明显的过渡。线粒体 DNA 也存在平行的转变，但仍有待充分记录。数据支持分化谱系的次级接触后的杂交区存在，而不是原地物种形成。
