Abstract
Understanding the mechanisms underlying the assembly of communities has long been the goal of many ecological studies. While several studies have evaluated community wide ecological assembly, fewer have focused on investigating the impacts of individual members within a community or assemblage on ecological assembly. Here, we adapted a previous null model β-nearest taxon index (βNTI) to measure the contribution of individual features within an ecological community to overall assembly. This new metric, called feature-level βNTI (βNTIfeat), enables researchers to determine whether ecological features (e.g., individual microbial taxa) contribute to divergence, convergence, or have insignificant impacts across spatiotemporally resolved metacommunities or meta-assemblages. Using βNTIfeat, we revealed that unclassified microbial lineages often contributed to community divergence while diverse groups (e.g., Crenarchaeota, Alphaproteobacteria, and Gammaproteobacteria) contributed to convergence. We also demonstrate that βNTIfeat can be extended to other ecological assemblages such as organic molecules comprising organic matter (OM) pools. OM had more inconsistent trends compared to the microbial community though CHO-containing molecular formulas often contributed to convergence, while nitrogen and phosphorus-containing formulas contributed to both convergence and divergence. A network analysis was used to relate βNTIfeat values from the putatively active microbial community and the OM assemblage and examine potentially common contributions to ecological assembly across different communities/assemblages. This analysis revealed that P-containing formulas often contributed to convergence/divergence separately from other ecological features and N-containing formulas often contributed to assembly in coordination with microorganisms. Additionally, members of Family Geobacteraceae were often observed to contribute to convergence/divergence in conjunction with both N- and P-containing formulas, suggesting a coordinated ecological role for family members and the nitrogen/phosphorus cycle. Overall, we show that βNTIfeat offers opportunities to investigate the community or assemblage members, which shape the phylogenetic or functional landscape, and demonstrate the potential to evaluate potential points of coordination across various community types.
Highlights
Evaluating the processes which govern community diversity is often the goal of ecological studies across all ecosystems (Swenson et al, 2006; Kraft et al, 2007; Gilbert and Bennett, 2010; Smith and Lundholm, 2010; Chase and Myers, 2011; George et al, 2011; Stegen et al, 2013; Herren and McMahon, 2017; Zhou and Ning, 2017; Danczak et al, 2020b)
We propose that a new metric called feature-level β-nearest taxon index based upon an existing null modeling framework will provide these benefits. βNTI is capable in assessing the assembly dynamics associated with ecological metacommunities and organic matter (OM) meta-metabolomes/ assemblages and we show that it can be adapted to featurelevel analyses. βNTI has been used extensively to study assembly processes
Feature-level β-nearest taxon index is a novel metric that enables researchers to investigate the contributions to ecological convergence and divergence with a given metacommunity or meta-assemblage
Summary
Evaluating the processes which govern community diversity is often the goal of ecological studies across all ecosystems (Swenson et al, 2006; Kraft et al, 2007; Gilbert and Bennett, 2010; Smith and Lundholm, 2010; Chase and Myers, 2011; George et al, 2011; Stegen et al, 2013; Herren and McMahon, 2017; Zhou and Ning, 2017; Danczak et al, 2020b). Researchers have focused on understanding the processes governing the composition of organic molecules or metabolites within organic matter (OM) assemblages (Danczak et al, 2020a, 2021). While methods might vary in how researchers investigate these processes (e.g., variation partitioning, trait-based analyses, and null modeling), each study attempts to determine when, where, and how various ecological assembly processes give rise to specific community/ assemblage configurations. By better understanding the distribution of these processes and the circumstances under which they dominate, we will be able to better understand the fundamental principles governing community/assemblage structure. Less attention has been paid to the impact of ecological processes on individual community/assemblage members or to the impact of individual members on ecological assembly. In order to limit confusion, both biological and chemical members are referred to as “features,” while biological communities and OM assemblages are referred to as “communities” (Table 1)
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