Functional Redundancy in Ocean Microbiomes Controls Trait Stability

Abstract

6 Theory predicts that functional redundancy in microbial communities increases trait stability, meaning that traits or functions are less likely to be lost from the community when species go extinct. However, few experiments have empirically tested this prediction, especially in the context of microbial communities and at the landscape scale. In part, the lack of metrics for functional redundancy in microbial ecosystems has prevented addressing this question. In a companion manuscript we proposed a quantitative metric for functional redundancy called Contribution Evenness (CE) that is optimized to reflect trait stability. Here, we use CE to predict the stability of marine microbial functions to species and transcription loss. Using transcriptomes deposited in the Ocean Microbial Reference Gene Catalog (OM-RGC.v2), a catalog of genes and transcripts sequenced by the TARA Ocean expedition, we quantified the functional redundancy for 4,314 KEGG Orthologs (KOs) across marine sites. Functional redundancy was highly correlated with a latent variable consisting of four ocean physiochemical parameters: oxygen and chlorophyll a concentrations, depth, and salinity. Functional redundancy was higher at the poles than in non-polar regions. Simultaneously, regional β-diversity for individual functions was higher for functions with higher functional redundancy. These observations provide evidence that higher functional redundancy indicates increased stability of microbial ecosystem functions on spatiotemporal scales consistent with surface ocean mixing. We suggest that future changes in ocean physiochemistry could likely influence this stability for functions with lower functional redundancy. (which was not certified by peer review) is the author/funder, who has granted bioRxiv a…