Across the distribution of the Caspian whipsnake (Dolichophis caspius), populations have become increasingly disconnected due to habitat alteration. To understand population dynamics and this widespread but locally endangered snake’s adaptive potential, we investigated population structure, admixture, and effective migration patterns. We took a landscape-genomic approach to identify selected genotypes associated with environmental variables relevant to D. caspius. With double-digest restriction-site associated DNA (ddRAD) sequencing of 53 samples resulting in 17,518 single nucleotide polymorphisms (SNPs), we identified 8 clusters within D. caspius reflecting complex evolutionary patterns of the species. Estimated Effective Migration Surfaces (EEMS) revealed higher-than-average gene flow in most of the Balkan Peninsula and lower-than-average gene flow along the middle section of the Danube River. Landscape genomic analysis identified 751 selected genotypes correlated with 7 climatic variables. Isothermality correlated with the highest number of selected genotypes (478) located in 41 genes, followed by annual range (127) and annual mean temperature (87). We conclude that environmental variables, especially the day-to-night temperature oscillation in comparison to the summer-to-winter oscillation, may have an important role in the distribution and adaptation of D. caspius.

中文翻译：

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东欧和西亚广泛分布的蛇 Dolicophis caspius (Gmelin, 1789) 的景观基因组学

在里海鞭蛇 (Dolichophis caspius) 的分布范围内，由于栖息地的改变，种群之间的联系越来越紧密。为了了解种群动态以及这种广泛存在但在当地濒临灭绝的蛇的适应潜力，我们调查了种群结构、混合和有效的迁移模式。我们采用景观基因组方法来确定与 D. caspius 相关的环境变量相关的选定基因型。通过对 53 个样本进行双酶切限制性位点相关 DNA (ddRAD) 测序，产生 17,518 个单核苷酸多态性 (SNP)，我们在 D. caspius 中鉴定了 8 个集群，反映了该物种的复杂进化模式。估计的有效迁移表面 (EEMS) 显示巴尔干半岛大部分地区的基因流量高于平均水平，而多瑙河中段的基因流量低于平均水平。景观基因组分析确定了与 7 个气候变量相关的 751 个选定基因型。等温性与位于 41 个基因中的最高数量的选定基因型 (478) 相关，其次是年范围 (127) 和年平均温度 (87)。我们得出结论，环境变量，尤其是与夏季到冬季振荡相比的昼夜温度振荡，可能在 D. caspius 的分布和适应中具有重要作用。等温性与位于 41 个基因中的最高数量的选定基因型 (478) 相关，其次是年范围 (127) 和年平均温度 (87)。我们得出结论，环境变量，尤其是与夏季到冬季振荡相比的昼夜温度振荡，可能对 D. caspius 的分布和适应具有重要作用。等温性与位于 41 个基因中的最高数量的选定基因型 (478) 相关，其次是年范围 (127) 和年平均温度 (87)。我们得出结论，环境变量，尤其是与夏季到冬季振荡相比的昼夜温度振荡，可能对 D. caspius 的分布和适应具有重要作用。