Prey Breakdown and Nitrogen Cycling: Functional Insights from Bacteria Isolated from Carnivorous Plants

Biodiversity–ecosystem function (BEF) relationships have been a major topic since the 1990s, because of sustainability and extinction crises, although BEF relationships are not easily correlated with habitat, taxa, or diversity. We proposed and tested two predictors for BEF relationship shapes: (i) individual species abundance (indicating coexistence and competitive abilities) and functional performance, and (ii) specific functions underlying a broader function. Darlingtonia californica is a carnivorous plant with modified leaves housing bacteria that contribute to insect degradation and nitrogen provision. We isolated 14 distinct bacterial strains from D. californica leaf fluid, grew the isolates in monocultures and mixed cultures, and evaluated each using insect degradation assays and protein, ammonia, nitrate, chitinase, and protease quantification assays. We asked three questions related to our two predictors of BEF shapes: First, can function of a bacterial community be predicted based on functions of individual species? Second, are there correlations between bacterial species function and abundance change? Finally, does degradative function in bacterial communities correlate with nitrogen-related processes in the context of this key limiting nutrient? We found that increased degradative function correlated with decreased species abundance changes, highly functioning mixed cultures could result from both highly or moderately functioning isolates, and degradative function did not rely on tested nitrogen-related functions. BEF relationships present a trade-off between degradative function and bacterial abundance changes, but not with the specific nitrogen assays. Although species with strong functional contributions can also be good competitors, they may also be poor competitors or play complex roles in community assembly. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .