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策略，可快速产生新的基因型与表型，助力物种开拓新生境并快速适应环境变化。本研究以池蛙复合种（Pelophylax esculentus complex）的水蛙为研究模型，以探讨物种形成背景下的新近杂交与多倍化过程。该复合种包含两个亲本物种：佩氏池蛙（Pelophylax lessonae，基因型LL）与里氏池蛙（Pelophylax ridibundus，基因型RR），以及多种二倍体（LR）和三倍体（LLR、LRR）杂交型类群，上述类群统称为P. esculentus。具体而言，本研究比对了欧洲范围内二倍体与三倍体杂交型水蛙的地理分布与遗传多样性，以解析其起源、维持机制以及在杂交物种形成中可能发挥的作用。研究发现，不同杂交型与亲本基因型的水蛙在欧洲的分布并不均匀；其遗传多样性格局由纬度、经度以及亲本物种的存在与否决定，而与三倍体的存在无关。欧洲中部与东部地区的遗传多样性最高，西北部地区则最低。该多样性梯度可由冰期后从东南冰期避难所向外扩散过程中遗传多样性的逐步衰减得到解释。基于微卫星（microsatellite）数据构建的谱系关系清晰表明，杂交型类群具有多起源特征，且包含大量多样化的亲本基因组组合。不含任何亲本物种的混合倍性种群（即全杂交种群）中的水蛙，可被视为正处于杂交物种形成进程中的演化单元。维持这类全杂交种群需要二倍体与三倍体之间持续进行基因组交换，本文同时探讨了其可能的替代演化路径。