Table_1_Microbiome Differentiation Among Coexisting Nematode Species in Estuarine Microhabitats: A Metagenetic Analysis.xlsx

Resource partitioning is a mechanism for niche differentiation which can facilitate coexistence of species at local scales. Insights into resource use and niche differentiation of functionally similar and/or taxonomically closely related species are scant, especially so for small organisms that dominate marine sediments in terms of abundance and species richness. In this study we characterized the microbiomes of 10 bacterivorous nematode species co-occurring in various estuarine microhabitats using 16S rRNA metabarcoding to address their resource utilization. We investigated microbiome diversity and composition of nematodes collected from six microhabitats in the field: Fucus spiralis, Fucus vesiculosus, fresh and decomposing thalli of Ulva sp., and attached and detached leaves of Spartina anglica. The 10 species belonged to three different families, and included congeneric and morphologically cryptic species. The microbiome of species sharing their microhabitats showed a substantial overlap, suggesting that resource differentiation of species within a microhabitat was rather limited at time of sampling. Microbiomes of the same nematode species found in different microhabitats were also not strongly differentiated. Temporal divergence in resource use may occur, as suggested by temporally divergent microbiome composition of nematodes associated with Ulva sp. The observed high intraspecific variability in microbiome composition of nematodes may be the principal factor explaining the lack of microbiome differentiation among species or microhabitats and may illustrate individual specialization in resource use as a consequence of substantial intraspecific competition.

资源划分（resource partitioning）是生态位分化（niche differentiation）的一类机制，可助力物种在局域尺度下实现共存。当前针对功能相似且/或分类学近缘物种的资源利用与生态位分化研究仍较为匮乏，对于在丰度与物种丰富度上主导海洋沉积物的小型生物而言，这一缺口尤为显著。本研究借助16S rRNA 宏条形码（16S rRNA metabarcoding）技术，对多种河口微生境中共存的10种食细菌线虫的微生物组进行了表征，以解析其资源利用模式。研究团队对野外采集自6种微生境的线虫微生物组多样性与组成展开了分析，这些微生境包括：墨角藻（Fucus spiralis）、囊状墨角藻（Fucus vesiculosus）、石莼属（Ulva sp.）的新鲜与腐解藻体，以及大米草（Spartina anglica）的附着叶与脱落叶。该10个物种分属3个不同的科，其中涵盖同属物种与形态隐存物种。共享同一微生境的物种，其微生物组存在显著重叠，这表明在采样时点，同一微生境内部的物种间资源分化程度相对有限。在不同微生境中发现的同一线虫物种，其微生物组同样未呈现出明显分化。与石莼属（Ulva sp.）相关的线虫微生物组组成随时间呈现出分化特征，这提示资源利用可能存在时间维度上的分化。本研究观测到的线虫微生物组组成具有较高的种内变异，这或许是解释不同物种或微生境间微生物组未出现显著分化的核心因素，同时也可印证：在强烈的种内竞争作用下，线虫个体在资源利用上存在特化现象。