A major goal of metacommunity ecology is to infer the local- and regional-scale processes that underlie community assembly. In dendritic ecological networks, branching patterns and directional flow can alter the balance between local and regional factors during assembly. Vertical habitat structure may further affect community assembly in dendritic metacommunities. In this study, we analyzed the bacterial metacommunity of a fifth-order mountain stream network to assess differences in community assembly (1) between planktonic and benthic habitats, (2) across spatial scales, and (3) between headwater and downstream regions of the network. Using taxonomic and phylogenetic null modeling, we found habitat-specific spatial patterns of community assembly across the dendritic network. Compositional differences between planktonic and benthic communities were maintained by variable selection, but we also found evidence of local dispersal limitation between the two habitats. Planktonic community assembly was scale dependent, transitioning from homogeneous selection at local scales to variable selection at regional scales, while benthic community assembly was less scale dependent. Variable selection structured headwaters in both habitat types, but downstream communities were primarily structured by homogeneous selection, especially in sediments. Taken together, our results show that vertical habitat structure contributes to the scale-dependent processes of community assembly across the dendritic metacommunity.

元社区生态学的主要目标是推断构成社区集会基础的地方和区域规模的过程。在树状生态网络中，分支模式和定向流动会在组装过程中改变局部和区域因素之间的平衡。垂直生境结构可能进一步影响树突状群落中的群落聚集。在这项研究中，我们分析了五阶山区河流网络的细菌元群落，以评估社区组装的差异（1）浮游生境和底栖生境之间，（2）跨空间尺度以及（3）上游水源与下游区域之间的差异。网络。使用分类学和系统发育零模型，我们发现了整个树突网络中特定的栖息地特定的空间格局。浮游和底栖群落之间的组成差异通过变量选择得以维持，但我们也发现了两个生境之间局部散布限制的证据。浮游生物群落的组装与规模有关，从局部规模的同质选择过渡到区域尺度的变量选择，而底栖生物群落的规模依赖性较小。两种生境类型中可变选择的源头都有水源，但下游社区主要是由均质的选择构成的，尤其是在沉积物中。两者合计，我们的结果表明，垂直的栖息地结构有助于整个树突状元社区的社区组装的规模依赖过程。浮游生物群落的组装与规模有关，从局部规模的同质选择过渡到区域尺度的变量选择，而底栖生物群落的规模依赖性较小。两种生境类型中可变选择的源头都有水源，但下游社区主要是由均质的选择构成的，尤其是在沉积物中。两者合计，我们的结果表明，垂直的栖息地结构有助于整个树突状元社区的社区组装的规模依赖过程。浮游生物群落的组装与规模有关，从局部规模的同质选择过渡到区域尺度的变量选择，而底栖生物群落的规模依赖性较小。两种生境类型中可变选择的源头都有水源，但下游社区主要是由均质的选择构成的，尤其是在沉积物中。两者合计，我们的结果表明，垂直的栖息地结构有助于整个树突状元社区的社区组装的规模依赖过程。但是下游社区主要是由均质选择构成的，尤其是在沉积物中。两者合计，我们的结果表明，垂直的栖息地结构有助于整个树突状元社区的社区组装的规模依赖过程。但是下游社区主要是由均质选择构成的，尤其是在沉积物中。两者合计，我们的结果表明，垂直的栖息地结构有助于整个树突状元社区的社区组装的规模依赖过程。