Data from: Geographical parthenogenesis and population genetic structure in the alpine species Ranunculus kuepferi (Ranunculaceae)

Geographical parthenogenesis describes the enigmatic phenomenon that asexual organisms have larger distribution areas than their sexual relatives, especially in previously glaciated areas. Classical models suggest temporary advantages to asexuality in colonization scenarios because of uniparental reproduction and clonality. We analyzed population genetic structure and self-fertility of the plant species Ranunculus kuepferi on 59 populations from the whole distribution area (European Alps, Apennines and Corsica). Amplified fragment length polymorphisms (AFLPs) and five microsatellite loci revealed individual genotypes for all populations and mostly insignificant differences between diploid sexuals and tetraploid apomicts in all measures of genetic diversity. Low frequencies of private AFLP fragments/simple sequence repeat alleles, and character incompatibility analyses suggest that facultative recombination explains best the unexpectedly high genotypic diversity of apomicts. STRUCTURE analyses using AFLPs revealed a higher number of partitions and a stronger geographical subdivision for diploids than for tetraploids, which contradicts expectations of standard gene flow models, but indicates a reduction of genetic structure in asexuals. Apomictic populations exhibited high admixture near the sexual area, but appeared rather uniform in remote areas. Bagging experiments and analyses of pollen tube growth confirmed self-fertility for pollen-dependent apomicts, but self-sterility for diploid sexuals. Facultative apomixis combines advantages of both modes of reproduction: uniparental reproduction allows for rapid colonization of remote areas, whereas facultative sexuality and polyploidy maintains genetic diversity within apomictic populations. The density dependence of outcrossing limits range expansions of sexual populations.

地理孤雌生殖（Geographical parthenogenesis）指的是无性生殖生物较其有性近缘类群拥有更广分布范围的奇特现象，这一现象在曾经历冰川作用的区域尤为显著。经典模型指出，由于单性繁殖与克隆特性，无性生殖在拓殖场景中具备暂时性优势。我们针对覆盖全分布范围（欧洲阿尔卑斯山、亚平宁山脉与科西嘉岛）的59个种群的植物物种Ranunculus kuepferi，分析其种群遗传结构与自交育性。扩增片段长度多态性（Amplified fragment length polymorphisms, AFLPs）与5个微卫星位点（microsatellite loci）的分析结果表明，所有种群均可检出个体基因型；在各项遗传多样性指标上，二倍体有性种群与四倍体无融合生殖类群（apomicts）间大多无显著差异。私有AFLP片段与简单序列重复（simple sequence repeat, SSR）等位基因的低检出频率，以及性状不相容性分析结果均表明，兼性重组（facultative recombination）最能解释无融合生殖类群出人意料的高基因型多样性。基于AFLPs的STRUCTURE群体结构分析结果显示，相较于四倍体类群，二倍体类群拥有更多的遗传组分分区与更强的地理分化模式；这一结果与标准基因流模型的预期相悖，却表明无性生殖类群的遗传结构有所减弱。无融合生殖种群在有性类群分布区附近表现出较高的遗传混合度，但在偏远区域则呈现出较为均一的遗传特征。套袋实验与花粉管生长分析证实，依赖花粉的无融合生殖类群具备自交育性，而二倍体有性类群则表现为自交不亲和。兼性无融合生殖（facultative apomixis）整合了两种生殖模式的优势：单性繁殖可实现偏远区域的快速拓殖，而兼性有性生殖与多倍体特性则维持了无融合生殖种群内部的遗传多样性。异交的密度依赖性限制了有性种群的范围扩张。