Department of Animal Ecology and Systematics, Justus Liebig University Giessen, Giessen, Germany.
Institute of Biology, Faculty of Natural Sciences, Ss. Cyril and Methodius University, Skopje, Macedonia.
J Evol Biol. 2018 Dec;31(12):1969-1975. doi: 10.1111/jeb.13368. Epub 2018 Aug 29.
Due to the ubiquity and high dispersal capacity of unicellular eukaryotes, their often extraordinary diversity found in isolated and long-lived ecosystems such as ancient lakes is typically attributed to multiple colonization events rather than to in situ speciation. However, respective evolutionary studies are very scarce and the often high number of species flocks in ancient lakes across multicellular taxa raises the question whether unicellular species, such as diatoms, may radiate as well. Here, we use an integrative approach that includes molecular data from benthic diatom species of the genus Aneumastus endemic to ancient Lake Ohrid, fossil data obtained from the sediment record of a recent deep-drilling project and biogeographical information to test if this group, indeed, constitutes a species flock. Molecular-clock and phylogenetic analyses indicate a young monophyletic group of several endemic species. Molecular, fossil and biogeographical data strongly suggest a rapid intralacustrine diversification, which was possibly triggered by the emergence of novel habitats. This finding is the first evidence for a species flock in diatoms and suggests that in situ speciation is also a relevant evolutionary process for unicellular eukaryotes in isolated ecosystems.
由于单细胞真核生物的普遍存在和高分散能力，它们在古老湖泊等孤立和长寿的生态系统中通常表现出非凡的多样性，这通常归因于多次殖民事件，而不是原地物种形成。然而，各自的进化研究非常稀缺，而且在古老湖泊中经常存在大量的多细胞生物物种群，这就提出了一个问题，即单细胞生物，如硅藻，是否也能辐射形成。在这里，我们采用了一种综合的方法，包括来自古老的奥赫里德湖特有种底栖硅藻属的分子数据、最近深钻项目的沉积物记录中获得的化石数据以及生物地理信息，以检验这一组是否确实构成了一个物种群。分子钟和系统发育分析表明，这是一个年轻的单系的几个特有种群体。分子、化石和生物地理数据强烈表明，湖泊内部的快速多样化是由新栖息地的出现引发的。这一发现是硅藻物种群的第一个证据，表明原地物种形成也是孤立生态系统中单细胞真核生物的一个相关进化过程。
