Most animals, including sponges (Porifera), have species‐specific microbiomes. Which genetic or environmental factors play major roles structuring the microbial community at the intraspecific level in sponges is, however, largely unknown. In this study, we tested whether geographic location or genetic structure of conspecific sponges influences their microbial assembly. For that, we used three sponge species with different rates of gene flow, and collected samples along their entire distribution range (two from the Mediterranean and one from the Southern Ocean) yielding a total of 393 samples. These three sponge species have been previously analysed by microsatellites or single nucleotide polymorphisms, and here we investigate their microbiomes by amplicon sequencing of the microbial 16S rRNA gene. The sponge Petrosia ficiformis, with highly isolated populations (low gene flow), showed a stronger influence of the host genetic distance on the microbial composition than the spatial distance. Host‐specificity was therefore detected at the genotypic level, with individuals belonging to the same host genetic cluster harbouring more similar microbiomes than distant ones. On the contrary, the microbiome of Ircinia fasciculata and Dendrilla antarctica ‐ both with weak population structure (high gene flow) ‐ seemed influenced by location rather than by host genetic distance. Our results suggest that in sponge species with high population structure, the host genetic cluster influence the microbial community more than the geographic location.

中文翻译：

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在特异性方面-微生物组主要在高度结构化的人群中反映海绵的遗传簇。

大多数动物，包括海绵（Porifera），都有特定物种的微生物群落。然而，究竟哪种遗传因素或环境因素在构成海绵内种内水平的微生物群落结构中起主要作用尚不清楚。在这项研究中，我们测试了同种海绵的地理位置或遗传结构是否会影响其微生物的组装。为此，我们使用了三种海绵，它们具有不同的基因流速率，并在它们的整个分布范围内收集了样本（两个来自地中海，一个来自南大洋），总共产生了393个样本。这三个海绵物种以前已经通过微卫星或单核苷酸多态性进行了分析，在这里我们通过微生物16S rRNA基因的扩增子测序研究它们的微生物群。海绵高度分离种群（基因流量低）的花椒（Petrosia ficiformis）显示出宿主遗传距离对微生物组成的影响要强于空间距离。因此，在基因型水平上检测到了宿主特异性，属于同一宿主基因簇的个体比远处的个体具有更多相似的微生物。相反，人口结构较弱（高基因流量）的Iscinia fasciculata和Dendrilla antarctica微生物组似乎受位置而不是宿主遗传距离的影响。我们的结果表明，在具有高种群结构的海绵物种中，宿主遗传簇对微生物群落的影响大于地理位置。