Soil protists play a crucial role in terrestrial ecosystems and often show immense taxonomic diversity. However, for many groups, distribution patterns remain largely unknown. We investigated range-wide intraspecific diversity of a specialized airborne protist (Didymium nivicola Meyl.) that occupies a narrow ecological niche associated with long-lasting snow cover. We sampled 122 collections covering all areas where the species was recorded worldwide. We obtained 105 and 41 sequences of small ribosomal subunit rDNA (SSU) and elongation factor 1-alpha (EF1A), respectively. While the species is very diverse in the austral Andes, Southern Hemisphere (SH; 17 SSU ribotypes and 12 EF1A genotypes identified), its populations are genetically uniform across three continents of the Northern Hemisphere (NH; single ribotype, single genotype). Our results indicate the austral Andes as a possible diversification centre for D. nivicola where populations seem to reproduce sexually. Two main parts of the range display highly contrasting genetic patterns, thus biogeographical history and dynamics. Current distribution of D. nivicola in the NH is likely a result of a dispersal event from the SH and subsequent long-distance dispersal (LDD) that might be associated with a shift to asexual mode of reproduction.

土壤原生生物在陆地生态系统中扮演着至关重要的角色，并且经常表现出巨大的生物多样性。但是，对于许多群体而言，分布模式仍然很大程度上未知。我们调查了专业空降生物（Didymium nivicola梅尔（Meyl。），它具有与持久的积雪相关的狭窄生态位。我们采样了122个馆藏，涵盖了全世界记录该物种的所有区域。我们分别获得了105个和41个小核糖体亚基rDNA（SSU）和延伸因子1-alpha（EF1A）的序列。尽管该物种在南半球的安第斯山脉南部非常多样（SH;已鉴定出17种SSU核型和12种EF1A基因型），但其种群在北半球三大洲（NH;单一核型，单一基因型）在遗传上是一致的。我们的结果表明，南部的安第斯山脉可能是D. nivicola的多元化中心人口似乎有性繁殖的地方。该范围的两个主要部分显示出截然不同的遗传模式，从而显示了生物地理历史和动态。NH中D. nivicola的当前分布可能是来自SH的扩散事件和随后的长距离扩散（LDD）的结果，而后者可能与向无性繁殖方式的转变有关。