Marine sponges host diverse communities of microbial symbionts that expand the metabolic capabilities of their host, but the abundance and structure of these communities is highly variable across sponge species. Specificity in these interactions may fuel host niche partitioning on crowded coral reefs by allowing individual sponge species to exploit unique sources of carbon and nitrogen, but this hypothesis is yet to be tested. Given the presence of high sponge biomass and the coexistence of diverse sponge species, the Caribbean Sea provides a unique system in which to investigate this hypothesis. To test for ecological divergence among sympatric Caribbean sponges and investigate whether these trends are mediated by microbial symbionts, we measured stable isotope (δ13C and δ15N) ratios and characterized the microbial community structure of sponge species at sites within four regions spanning a 1700 km latitudinal gradient. There was a low (median of 8.2 %) overlap in the isotopic niches of sympatric species; in addition, host identity accounted for over 75% of the dissimilarity in both δ13C and δ15N values and microbiome community structure among individual samples within a site. There was also a strong phylogenetic signal in both δ15N values and microbial community diversity across host phylogeny, as well as a correlation between microbial community structure and variation in δ13C and δ15N values across samples. Together, this evidence supports a hypothesis of strong evolutionary selection for ecological divergence across sponge lineages and suggests that this divergence is at least partially mediated by associations with microbial symbionts.

中文翻译：

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微生物共生体和加勒比海绵的生态多样性：古代联系的新观点。

海洋海绵拥有各种微生物共生体群落，可扩展宿主的代谢能力，但这些群落的丰度和结构在海绵物种之间差异很大。这些相互作用的特异性可能会允许单个海绵物种利用独特的碳和氮源，从而在拥挤的珊瑚礁上加剧宿主的生态位分配，但这一假设尚待验证。鉴于高海绵生物量的存在以及多种海绵物种的共存，加勒比海提供了一个独特的系统来研究这一假设。为了测试加勒比同胞海绵之间的生态差异，并调查这些趋势是否由微生物共生体介导，我们测量了稳定的同位素（δ13C和δ15N）比，并表征了横跨1700 km纬度梯度的四个区域内站点上海绵物种的微生物群落结构。同胞物种的同位素生态位重叠率低（中位数为8.2％）；此外，同一地点内单个样本之间的δ13C和δ15N值以及微生物组群落结构差异中，宿主身份占75％以上。宿主系统发育中的δ15N值和微生物群落多样性也有很强的系统发生信号，并且整个样品中微生物群落结构与δ13C和δ15N值的变化之间也具有相关性。一起，