Marine sponge reefs usually comprise a complex array of taxonomically different sponge species, many of these hosting highly diverse microbial communities. The number of microbial species known to occupy a given sponge ranges from tens to thousands, bringing numerous challenges to their analysis. One way to deal with such complexity is to use a core microbiota approach, in which only prevalent and abundant microbes are considered. Here we aimed to test the strength and sensitivity of the core microbiota approach by applying different core definitions to 20 host sponge species. Application of increasingly stringent relative abundance and/or percentage occurrence thresholds to qualify as part of the core microbiota decreased the number of ‘core’ OTUs and phyla and, consequently, changed both alpha‐ and beta‐diversity patterns. Moreover, microbial co‐occurrence patterns explored using correlation networks were also affected by the core microbiota definition. The application of stricter thresholds resulted in smaller and less compartmentalized networks, with different keystone species. These results highlight that the application of different core definitions to phylogenetically disparate host species can result in the drawing of markedly different conclusions. Consequently, we recommend to assess the effects of different core community definitions on the specific system of study before considering its application.

中文翻译：

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在高度多样化的海绵礁上评估核心微生物群方法的强度和敏感性。

海洋海绵礁通常包含复杂的分类学上不同的海绵物种，其中许多包含高度多样化的微生物群落。已知占据给定海绵的微生物种类数以万计，这给分析带来许多挑战。解决这种复杂性的一种方法是使用核心微生物区系方法，其中仅考虑普遍存在和丰富的微生物。在这里，我们旨在通过对20种宿主海绵物种应用不同的核心定义来测试核心微生物群方法的强度和敏感性。越来越严格的相对丰度和/或百分比发生阈值的应用使有资格成为核心微生物群的一部分，减少了“核心” OTU和门的数量，因此改变了α-和β-多样性模式。此外，使用相关网络探索的微生物共生模式也受到核心微生物群定义的影响。严格的阈值的应用导致具有不同梯形失真种类的较小和较少分隔的网络。这些结果表明，将不同的核心定义应用于系统发育上互不相同的宿主物种可能会得出明显不同的结论。因此，我们建议在考虑将其应用之前，先评估不同核心社区定义对特定学习系统的影响。这些结果表明，将不同的核心定义应用于系统发育上互不相同的宿主物种可能会得出明显不同的结论。因此，我们建议在考虑将其应用之前，先评估不同核心社区定义对特定学习系统的影响。这些结果表明，将不同的核心定义应用于系统发育上互不相同的宿主物种可能会得出明显不同的结论。因此，我们建议在考虑将其应用之前，先评估不同核心社区定义对特定学习系统的影响。