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

草蛇（Natrix natrix）是古北界最常见、分布最广的蛇类之一。最近的研究表明，其线粒体的地理亚种之间的主要不匹配划定和部分深刻分歧的线粒体分支。进一步出乎意料的发现是西部草蛇（N. n. helvetica）和东部草蛇（目前被鉴定为N. n.在莱茵河地区发现了两种新发现的不同线粒体谱系的接触区，这两种线粒体谱系横跨东欧草蛇的中欧范围。我们的项目更详细地分析了潜在的遗传模式，目的是仔细研究草蛇的分类和地理分布。我们使用大规模的采样从三个接触区的遗传谱系代表三个最深分歧的线粒体进化枝的草蛇加上新发现的中欧接触区。对于每个接触区，我们研究了可能的基因流不同的血统之间使用人口遗传和系统发育的方法的基础上13个微卫星位点和两个线粒体基因。作为第一个结果，我们可以表明，伊比利亚-马格里布草蛇代表了一个独特的物种（N。astreptophora），这是生殖很大程度上从地理上相邻的分类群（N. n. helvetica）。我们对另外两个接触区的初步研究结果为N. n. helvetica和N. n.纳特里克斯，被限制在一个狭窄的，10公里宽的带。与此相反，N. n.纳特里克斯这提供了证据，表明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。我们的分类学结论将建立在种群遗传学和地理学框架的基础上。现在已经很清楚，草蛇的分类需要大量的修改。此外，使用上述的标记系统，我们测试不同的地理学假说有关的冰川避难所的位置。根据我们的初步结果，所研究的谱系的冰川避难所位于南部巴尔干半岛的半岛。祖先的多态性显然不能解释所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.