Understanding the specificity and flexibility of the algal symbiosis-host association is fundamental for predicting how species occupy a diverse range of habitats. Here we assessed the algal symbiosis diversity of three species of larger benthic foraminifera from the genus Amphistegina and investigated the role of habitat and species identity in shaping the associated algal community. We used next-generation sequencing to identify the associated algal community, and DNA barcoding to identify the diatom endosymbionts associated with species of A. lobifera, A. lessonii, and A. radiata, collected from shallow habitats (< 15 m) in 16 sites, ranging from the Mediterranean Sea to French Polynesia. Next-generation sequencing results showed the consistent presence of Ochrophyta as the main algal phylum associated with all species and sites analysed. A significant proportion of phylotypes were classified as Chlorophyta and Myzozoa. We uncovered unprecedented diversity of algal phylotypes found in low abundance, especially of the class Bacillariophyta (i.e., diatoms). We found a significant influence of sites rather than host identity in shaping algal communities in all species. DNA barcoding revealed the consistent presence of phylotypes classified within the order Fragilariales as the diatoms associated with A. lobifera and A. lessonii, while A. radiata specimens host predominately diatoms of the order Triceratiales. We show that local habitat is the main factor influencing the overall composition of the algal symbiont community. However, host identity and the phylogenetic relationship among hosts is relevant in shaping the specific endosymbiont diatom community, suggesting that the relationship between diatom endosymbiont and hosts plays a crucial role in the evolutionary history of the genus Amphistegina. The capacity of Amphistegina species to associate with a diverse array of diatoms, and possibly other algal groups, likely underpins the ecological success of these crucial calcifying organisms across their extensive geographic range.

中文翻译：

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全球分布的大型底栖有孔虫Amphistegina藻类共生群落的多样性和灵活性

了解藻类共生-宿主关联的特异性和灵活性对于预测物种如何占据各种栖息地至关重要。在这里，我们评估了来自 Amphistegina 属的三种大型底栖有孔虫的藻类共生多样性，并研究了栖息地和物种身份在塑造相关藻类群落中的作用。我们使用下一代测序来识别相关的藻类群落，并使用 DNA 条形码来识别与 A. lobifera、A.lessii 和 A. radiata 物种相关的硅藻内共生体，这些物种是从 16 个地点的浅栖息地（< 15 m）收集的，从地中海到法属波利尼西亚。下一代测序结果表明，作为与所有分析物种和地点相关的主要藻门，赭藻门始终存在。很大比例的系统发育型被分类为绿藻门和Myzozoa。我们发现了在低丰度中发现的前所未有的藻类系统多样性，特别是 Bacillariophyta 类（即硅藻）。我们发现在塑造所有物种的藻类群落时，地点而不是宿主身份的显着影响。DNA 条形码揭示了分类在 Fragilariales 目内的系统型的一致存在，作为与 A. lobifera 和 A. courseii 相关的硅藻，而 A. radiata 标本主要以三角目硅藻为宿主。我们表明，当地栖息地是影响藻类共生群落整体组成的主要因素。然而，宿主身份和宿主之间的系统发育关系与塑造特定的内共生硅藻群落有关，表明硅藻内共生体和宿主之间的关系在 Amphistegina 属的进化历史中起着至关重要的作用。Amphistegina 物种与多种硅藻以及可能的其他藻类群相关联的能力可能是这些重要的钙化生物在其广泛的地理范围内的生态成功的基础。