Data from: Polar lakes may act as ecological islands to aquatic protists

A fundamental question in ecology is whether microorganisms follow the same patterns as multicellular organisms when it comes to population structure and levels of genetic diversity. Enormous population sizes, predominately asexual reproduction, and presumably high dispersal due to small body size could have profound implications on their genetic diversity and population structure. Here, we have analyzed the population genetic structure in a lake-dwelling microbial eukaryote (dinoflagellate) and tested the hypothesis that there is population genetic differentiation among nearby lake subpopulations. This dinoflagellate occurs in the marine-derived saline lakes of the Vestfold Hills, Antarctica, which are ice-covered most of the year. Clonal strains were isolated from four different lakes, and were genotyped using AFLP (Amplified Fragment Length Polymorphism). Our results show high genetic differentiation among lake populations despite their close geographical proximity (< 9 km). Moreover, genotype diversity was high within populations. Gene flow in this system is clearly limited, either due to physical or biological barriers. Our results discard the null hypothesis that there is free gene flow among protist lake populations. Instead, limnetic protist populations may differentiate genetically, and lakes act as ecological islands even on the microbial scale.生态学领域的一个核心问题在于：微生物在种群结构与遗传多样性层面，是否与多细胞生物遵循相同的演化模式。微生物庞大的种群规模、以无性繁殖为主的繁殖策略，以及因体型微小而被推测具备的高效扩散能力，均可能对其遗传多样性与种群结构产生深远影响。本研究针对一种栖息于湖泊的真核微生物——甲藻（dinoflagellate），开展了种群遗传结构分析，并验证了“邻近湖泊亚种群间存在种群遗传分化”这一假说。该甲藻栖息于南极韦斯特福尔德丘陵（Vestfold Hills）的海洋源性咸水湖，这类湖泊一年中多数时段均被冰层覆盖。研究人员从四个独立湖泊中分离得到克隆菌株，并通过AFLP（扩增片段长度多态性，Amplified Fragment Length Polymorphism）技术完成基因分型。研究结果显示，尽管各湖泊地理间距极近（不足9公里），其种群间仍存在显著的遗传分化；同时，种群内部的基因型多样性同样处于较高水平。该系统中的基因流明显受限，其成因可能为物理屏障或生物学屏障。本研究结果否定了“湖栖原生生物种群间存在自由基因流”的零假设。由此可见，湖沼原生生物种群可能发生遗传分化，即便在微生物尺度下，湖泊同样可作为生态岛屿发挥作用。