Phylogenetic and metabolic diversity have contrasting effects on the ecological functioning of bacterial communities

Abstract

<jats:p>Biodiversity can affect microbial ecosystem functioning because greater numbers of species, and their associated genetic and metabolic differences, can contribute at different times and contexts to overall ecosystem functioning. Quantifying the relative contributions of microbial species to ecosystem functioning is challenging, because of the distinct mechanisms that are associated with their phylogenetic diversity vs. their metabolic diversity. We used synthetic bacterial communities to test the independent effects of two aspects of biodiversity, phylogenetic and metabolic diversity, on community ecological functioning. We expected that metabolic diversity, as a direct measure of species functional traits, would be associated with greater ecological function. Contrastingly, since phylogenetic diversity is inherently a metric based on neutral genetic markers, it should have no influence. Moreover, we hypothesised that phylogenetically related species would impact species interactions and coexistence, therefore amplifying the influence of metabolic diversity. To study these effects, we used bacterial isolates to construct communities with different diversity traits and employed exoenzyme activities (EEAs) and total available carbon (TAC) from substrates as proxies of bacterial functioning. Using linear models to examine the effects of one diversity treatment while controlling for the other, we found that they did not meet most of our expectations. Phylogenetic diversity strongly influenced community ecological functioning and metabolic diversity exhibited significantly negative relationships. When controlling for different substrates, EEAs increased along with phylogenetic diversity but decreased with metabolic diversity. In addition, the strength of the diversity effects was depended on the substrates. EEAs on carbohydrates showed a strong positive relationship with phylogenetic diversity and a strong negative relationship with metabolic diversity, while EEAs on fatty acids typically showed no relationship at all. Furthermore, EEAs of phylogenetically similar groups were strongly affected by within-genus interactions. We concluded that both phylogenetic and metabolic diversity have complicated and contrasting effects, which furthermore depended on the ecological function under examination - diversity effects were depended on substrate chemistry and the molecular mechanisms related to each substrate's degradation. This highlights the importance of investigating individual aspects of biodiversity but also their interactions and the variations within the biological mechanisms and processes that underscore them, to improve ecological theory.</jats:p>

Metabolic dissimilarity determines the establishment of cross-feeding interactions in bacteria

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Functional and compositional changes in the fecal microbiome of a shorebird during pre-migratory weight gain

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