Data from: Genetic diversity and distribution patterns of diploid and polyploid hybrid water frog populations (Pelophylax esculentus complex) across Europe

Polyploidization is a rare yet sometimes successful way for animals to rapidly create geno- and phenotypes that may colonize new habitats and quickly adapt to environmental changes. In this study, we use water frogs of the Pelophylax esculentus complex, comprising two species (Pelophylax lessonae, genotype LL; Pelophylax ridibundus, RR) and various diploid (LR) and triploid (LLR, LRR) hybrid forms, summarized as P. esculentus, as a model for studying recent hybridization and polyploidization in the context of speciation. Specifically, we compared the geographic distribution and genetic diversity of diploid and triploid hybrids across Europe to understand their origin, maintenance and potential role in hybrid speciation. We found that different hybrid and parental genotypes are not evenly distributed across Europe. Rather, their genetic diversity is structured by latitude and longitude and the presence/absence of parental species but not of triploids. Highest genetic diversity was observed in central and eastern Europe, the lowest in the northwestern parts of Europe. This gradient can be explained by the decrease in genetic diversity during postglacial expansion from southeastern glacial refuge areas. Genealogical relationships calculated on the basis of microsatellite data clearly indicate that hybrids are of multiple origin and include a huge variety of parental genomes. Water frogs in mixed-ploidy populations without any parental species (i.e. all-hybrid populations) can be viewed as evolutionary units that may be on their way towards hybrid speciation. Maintenance of such all-hybrid populations requires a continuous exchange of genomes between diploids and triploids, but scenarios for alternative evolutionary trajectories are discussed.多倍化（polyploidization）是一种罕见但偶获成功的动物演化路径，可快速产生新的基因型与表型，助力物种拓殖新生境并快速适应环境变化。本研究以池蛙复合群（Pelophylax esculentus complex）为研究模型，该复合群包含两个亲本物种——莱桑池蛙（Pelophylax lessonae，基因型LL）与里德利池蛙（Pelophylax ridibundus，基因型RR），以及多种基因型为LR的二倍体（diploid）和基因型为LLR、LRR的三倍体（triploid）杂交型类群，上述类群统称为P. esculentus，用于解析物种形成背景下的近期杂交与多倍化过程。具体而言，我们对比了欧洲全境二倍体与三倍体杂交蛙的地理分布格局与遗传多样性特征，以阐明其起源、维持机制及其在杂交物种形成中的潜在作用。研究发现，不同杂交型与亲本基因型的地理分布在欧洲并非均匀分布，其遗传多样性格局受纬度、经度及亲本物种存在与否的调控，而非受三倍体的影响。欧洲中东部区域的遗传多样性最高，西北部区域则最低，这一多样性梯度可通过冰期后从东南冰期避难所向外扩张过程中遗传多样性的逐步衰减得到解释。基于微卫星（microsatellite）分子标记数据构建的谱系关系分析清晰表明，杂交蛙具有多重起源，且包含极为多样的亲本基因组。不含任何亲本物种的混合倍性种群（即全杂交种群）中的池蛙，可被视为正处于杂交物种形成进程中的独立演化单元。维持这类全杂交种群需要二倍体与三倍体之间持续的基因组交流，本文同时探讨了其可能的替代演化路径。