Table_1_Diverse Internal Symbiont Community in the Endosymbiotic Foraminifera Pararotalia calcariformata: Implications for Symbiont Shuffling Under Thermal Stress.xlsx

Many shallow-water tropical and subtropical foraminifera engage in photosymbiosis with eukaryotic microalgae. Some of these foraminifera appear to harbor a diverse consortium of endosymbiotic algae within a single host. Such apparent ability to contain different symbionts could facilitate change in symbiont community composition (symbiont shuffling) and mediate the ecological success of the group in a changing environment. However, the discovery of the intra-individual symbiont diversity was thus far based on symbiont culturing, which provides strong constraints on the vitality of the identified algae but provides poor constraints on their initial abundance and thus functional relevance to the host. Here we analyze the algal symbiont diversity in Pararotalia calcariformata, a benthic foraminifera sampled at four stations, inside and outside of a thermal plume in the eastern Mediterranean coast of Israel. This species has recently invaded the Mediterranean, is unusually thermally tolerant and was described previously to host at least one different diatom symbiont than other symbiont-bearing foraminifera. Our results using genotyping and isolation of algae in culture medium, confirm multiple associations with different diatom species within the same individual. Both methods revealed spatially consistent symbiont associations and identified the most common symbiont as a pelagic diatom Minutocellus polymorphus. In one case, an alternative dominant symbiont, the diatom Navicula sp., was detected by genotyping. This diatom was the third most abundant species identified using standard algae culturing method. This method further revealed a spatially consistent pattern in symbiont diversity of a total of seventeen identified diatom species, across the studied localities. Collectively, these results indicate that P. calcariformata hosts a diverse consortium of diatom endosymbionts, where different members can become numerically dominant and thus functionally relevant in a changing environment.

众多浅水热带和亚热带的孔虫与真核微藻进行光合共生。其中一些孔虫似乎能够在单个宿主体内承载多种内共生藻类的复杂群落。这种容纳不同共生生物的能力可能有助于共生生物群落组成（共生生物重组）的变化，并调节该群体在多变环境中的生态成功。然而，个体内共生生物多样性的发现迄今为止主要依赖于共生生物培养，这虽然对所识别的藻类的活力提供了强有力的约束，但对于它们的初始丰度和因此对宿主的机能相关性则提供了较差的约束。在本研究中，我们分析了在以色列东地中海海岸的热液羽流内外四个站点采集的底栖有孔虫 Pararotalia calcariformata 的藻类共生生物多样性。该物种近期侵入地中海，对温度的耐受性异常，之前的研究表明，与其他携带共生生物的有孔虫相比，它至少可以携带一种不同的硅藻共生生物。我们使用基因分型和文化介质中藻类的分离，证实了在同一个体内与不同硅藻物种存在多种关联。这两种方法均揭示了空间上一致的共生生物关联，并确定了最常见的共生生物为浮游硅藻 Minutocellus polymorphus。在一种情况下，通过基因分型检测到一种替代的主导共生生物，即硅藻 Navicula sp.，这是使用标准藻类培养方法确定的第三丰富物种。此方法进一步揭示了在研究地点的共生生物多样性空间上一致的模式，共识别了十七种硅藻物种。总体而言，这些结果表明，P. calcariformata 承载着多样化的硅藻内共生生物群落，其中不同的成员可以成为数量上的优势种，并在变化的环境中发挥机能上的相关性。