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.

地理单性生殖（Geographical parthenogenesis）指的是无性生殖生物相较于其有性近缘类群拥有更广分布范围的难以解释的反常现象，该现象在既往冰期覆盖区域中尤为显著。经典模型认为，由于单性繁殖与克隆特性，无性生殖在拓殖过程中具备临时性优势。本研究针对分布全域（涵盖欧洲阿尔卑斯山、亚平宁山脉及科西嘉岛）的59个种群，分析了库普费尔毛茛（Ranunculus kuepferi）的种群遗传结构与自交育性。扩增片段长度多态性（AFLPs）与5个微卫星（microsatellite）位点的分析结果显示，所有种群均检出独立基因型，且在各项遗传多样性指标上，二倍体有性个体与四倍体无融合生殖个体之间大多无显著差异。私有AFLP片段/简单序列重复（simple sequence repeat, SSR）等位基因的低出现频率，以及性状不相容分析结果均表明，兼性重组最能解释无融合生殖体意料之外的高基因型多样性。基于AFLPs的STRUCTURE群体结构分析显示，相较于四倍体无融合生殖个体，二倍体有性个体拥有更多的群体组分与更强的地理分化格局，这与标准基因流模型的预期相悖，但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基因混合程度，但在偏远区域则呈现出较为均一的遗传组成。套袋实验与花粉管生长分析证实，依赖花粉的无融合生殖个体具备自交育性，而二倍体有性个体则表现出自交不育特性。兼性无融合生殖整合了两种繁殖模式的优势：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性则能维持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。