How many species of grass snakes are out there? Phylogeography, gene flow across contact zones and taxonomy of Natrix natrix

草蛇（Natrix Natrix）是古北地区最常见和分布最广泛的蛇种之一。最近对其线粒体系统地理学的研究表明，亚种描述和部分深度分化的线粒体分支之间存在重大不匹配。进一步出乎意料的发现是，莱茵地区西部草蛇（N. N. helvetica）和东部草蛇（目前鉴定为N. N. natrix）线粒体单倍型的明确异种分布，以及在中欧东部草蛇的范围内发现了两个新鉴定的不同线粒体谱系的接触区。我们的项目更详细地分析了潜在的遗传模式，目的是仔细检查草蛇的分类和系统地理学。我们从三个遗传谱系的接触区进行大规模采样，这些接触区代表了草蛇的三个最深入的线粒体分支，以及新发现的中欧接触区。对于每个接触区，我们使用基于13个微卫星位点和两个线粒体基因的群体遗传学和系统发育方法来检查不同谱系之间可能的基因流动。作为第一个结果，我们可以证明伊比利亚-马格里布草蛇代表了一个独特的物种（N. astreptophora），它在繁殖上很大程度上与地理上邻近的分类群（N. N. helvetica）分离。我们对其他两个接触带的初步结果提供了证据，证明nn . N. helvetica和nn . N. natrix之间只有非常有限的杂交，被限制在一个狭窄的10公里宽的条带上。相比之下，在N. N. natrix中，遗传谱系之间存在广泛的混合。这为草蛇的不同分类群和遗传谱系代表了物种形成过程的不同阶段提供了证据。我们的分类学结论将建立在我们项目中获得的群体遗传和系统地理框架的基础上。现在已经很清楚，草蛇的分类需要进行实质性的修订。此外，利用上述标记系统，我们测试了关于冰川避难所位置的不同生物地理学假设。根据我们的初步结果，研究谱系的冰川避难所位于巴尔干半岛南部。祖先多态性显然不能解释观察到的线粒体变异。

The grass snake (Natrix natrix) is the most common and one of the most widely distributed snake species of the Palaearctic region. Recent research on its mitochondrial phylogeography has shown major mismatches between subspecies delineation and in part deeply divergent mitochondrial clades. Further unexpected findings were the clear-cut parapatric distribution of mitochondrial haplotypes of western grass snakes (N. n. helvetica) and eastern grass snakes (currently identified with N. n. natrix) in the Rhine region and the discovery of a contact zone of two newly identified distinct mitochondrial lineages running across the Central European range of eastern grass snakes. Our project analyses the underlying genetic patterns in more detail with the aim of scrutinizing taxonomy and phylogeography of grass snakes. We use large-scale sampling from three contact zones of genetic lineages representing the three most deeply divergent mitochondrial clades of grass snakes plus the newly discovered Central European contact zone. For each contact zone, we examine possible gene flow between distinct lineages using population genetic and phylogenetic approaches based on 13 microsatellite loci and two mitochondrial genes. As a first result, we could show that the Ibero-Maghrebian grass snake represents a distinct species (N. astreptophora), which is reproductively largely isolated from the geographically neighbouring taxon (N. n. helvetica). Our preliminary results for the other two contact zones provide evidence for only very limited hybridization between N. n. helvetica and N. n. natrix, being restricted to a narrow, 10-km-wide strip. By contrast, there is broad admixture between the genetic lineages within N. n. natrix. This provides evidence that the different taxa and genetic lineages of grass snakes represent different stages of the speciation process. Our taxonomic conclusions will be founded on the population genetic and phylogeographic framework to be obtained in our project. Already now it is clear that the taxonomy of the grass snake requires substantial revision. Moreover, using the above mentioned marker systems, we test different biogeographical hypotheses regarding the location of glacial refugia. According to our preliminary results, the glacial refugia of the examined lineages were located in the southern Balkan Peninsula. Ancestral polymorphism clearly cannot explain the observed mitochondrial variation.