Unicellular eukaryotic predators play a crucial role in the functioning of the ocean ecosystem by recycling nutrients and energy that are channeled to upper trophic levels. Traditionally, these evolutionarily diverse organisms have been combined into a single functional group (heterotrophic flagellates), overlooking their organismal differences. Here, we investigated four evolutionarily related species belonging to one cosmopolitan group of uncultured marine picoeukaryotic predators: marine stramenopiles (MAST)-4 (species A, B, C, and E). Co-occurrence and distribution analyses in the global surface ocean indicated contrasting patterns in MAST-4A and C, suggesting adaptation to different temperatures. We then investigated whether these spatial distribution patterns were mirrored by MAST-4 genomic content using single-cell genomics. Analyses of 69 single cells recovered 66 to 83% of the MAST-4A/B/C/E genomes, which displayed substantial interspecies divergence. MAST-4 genomes were similar in terms of broad gene functional categories, but they differed in enzymes of ecological relevance, such as glycoside hydrolases (GHs), which are part of the food degradation machinery in MAST-4. Interestingly, MAST-4 species featuring a similar GH composition (A and C) coexcluded each other in the surface global ocean, while species with a different set of GHs (B and C) appeared to be able to coexist, suggesting further niche diversification associated with prey digestion. We propose that differential niche adaptation to temperature and prey type has promoted adaptive evolutionary diversification in MAST-4. We show that minute ocean predators from the same phylogenetic group may have different biogeography and genomic content, which needs to be accounted for to better comprehend marine food webs.

单细胞真核捕食者通过循环利用输送到上层营养层的营养物质和能量，在海洋生态系统的功能中发挥着至关重要的作用。传统上，这些进化上多样化的生物体被组合成一个单一的功能群（异养鞭毛虫），忽略了它们的生物体差异。在这里，我们研究了四种进化相关的物种，属于未培养的海洋超核掠食者的一个世界性群体：海洋原生藻菌 (MAST)-4（物种 A、B、C 和 E）。全球表层海洋的共现和分布分析显示了 MAST-4A 和 C 的对比模式，表明对不同温度的适应。然后，我们使用单细胞基因组学研究了 MAST-4 基因组内容是否反映了这些空间分布模式。对 69 个单细胞的分析恢复了 66% 至 83% 的 MAST-4A/B/C/E 基因组，显示出显着的种间差异。 MAST-4 基因组在广泛的基因功能类别方面相似，但它们在生态相关酶方面有所不同，例如糖苷水解酶 (GH)，它是 MAST-4 中食品降解机制的一部分。有趣的是，具有相似 GH 组成（A 和 C）的 MAST-4 物种在全球海洋表面相互排斥，而具有不同 GH 组（B 和 C）的物种似乎能够共存，这表明与相关的生态位进一步多样化。与猎物的消化。我们认为，对温度和猎物类型的差异生态位适应促进了 MAST-4 的适应性进化多样化。 我们表明，来自同一系统发育群体的微小海洋捕食者可能具有不同的生物地理学和基因组内容，需要考虑到这一点以更好地理解海洋食物网。