Data from: Clonality, genetic diversity, and support for the diversifying selection hypothesis, in natural populations of a flower-living yeast

Vast amounts of effort have been devoted to investigate patterns of genetic diversity and structuring in plants and animals, but similar information is scarce for organisms of other kingdoms. The study of the genetic structure of natural populations of wild yeasts can provide insights on the ecological and genetic correlates of clonality, and on the generality of recent hypotheses postulating that microbial populations lack the potential for genetic divergence and allopatric speciation. Ninety-one isolates of the flower-living yeast Metschnikowia gruessii from southeastern Spain were DNA fingerprinted using AFLP markers. Genetic diversity and structuring was investigated with band-based methods and model- and nonmodel-based clustering. Linkage disequilibrium tests were used to assess reproduction mode. Microsite-dependent, diversifying selection was tested by comparing genetic characteristics of isolates from bumble bee vectors and different floral microsites. AFLP polymorphism (91%) and genotypic diversity were very high. Genetic diversity was spatially structured, as shown by AMOVA (Φst = 0.155) and clustering. The null hypothesis of random mating was rejected, clonality seeming the prevailing reproductive mode in the populations studied. Genetic diversity of isolates declined from bumble bee mouthparths to floral microsites, and frequency of five AFLP markers varied significantly across floral microsites, thus supporting the hypothesis of diversifying selection on clonal lineages. Wild populations of clonal fungal microbes can exhibit levels of genetic diversity and spatial structuring that are not singularly different from those shown by sexually reproducing plants or animals. Microsite-dependent, divergent selection can maintain high local and regional genetic diversity in microbial populations despite extensive clonality.

学界已投入大量精力探究动植物的遗传多样性与群体遗传结构模式，但针对其他生物界类群的同类研究信息仍较为匮乏。对野生酵母自然种群遗传结构的研究，可为解析无性繁殖的生态与遗传关联特征，以及验证近期提出的“微生物种群缺乏遗传分化与异地物种形成潜力”假说的普适性提供关键见解。本研究以采自西班牙东南部的91株花栖酵母*Metschnikowia gruessii*为研究材料，采用扩增片段长度多态性（Amplified Fragment Length Polymorphism, AFLP）标记开展DNA指纹图谱分析；通过基于条带的遗传分析方法、基于模型与非模型的聚类分析方法，对种群的遗传多样性与结构展开探究；采用连锁不平衡（Linkage disequilibrium）检验评估其繁殖模式；通过比较来自传粉媒介大黄蜂与不同花卉微生境的菌株的遗传特征，验证微生境依赖型多样化选择假说。结果显示，AFLP标记的多态性达91%，菌株的基因型多样性亦处于较高水平；分子方差分析（Analysis of Molecular Variance, AMOVA，Φst=0.155）与聚类结果均表明，种群遗传多样性存在空间结构；随机交配的零假设被拒绝，表明在所研究的种群中，无性繁殖为主要繁殖方式；菌株的遗传多样性从大黄蜂口器种群向花卉微生境种群逐渐降低，且5个AFLP标记的频率在不同花卉微生境间存在显著差异，这一结果支持了克隆谱系受微生境依赖型多样化选择作用的假说。本研究表明，无性繁殖的真菌微生物野生种群，其遗传多样性与空间结构水平，与有性繁殖的动植物种群并无显著差异；尽管存在广泛的无性繁殖，微生境依赖型趋异选择仍可维持微生物种群在局域与区域尺度上的高水平遗传多样性。