Resounding evidence that biological diversity is essential for the functioning of ecosystems has motivated a global campaign for the conservation of biodiversity. Current conservation and ecosystem-based management efforts focus on trait variation among species and populations to maintain ecosystem function. Yet, trait variation at the level of the individual is also important for ecological interactions, although the implications for ecosystem function and management are poorly understood.
Results/Conclusions
Here we show that individual-level trait variation drives ecosystem-scale processes. Specifically, we show that the supply and translocation of nitrogen (N), a nutrient that critically limits primary production, by individual fish (via excretion) is poorly predicted by population-level means, differing >80% of the time. Accounting for this individual-level variation nearly doubles the amount of N supplied by populations, which we show represents ~97% of the N supply to the ecosystem. Extending these results to test their implications for ecosystem-based management, we find that selective harvest that targets more active individuals reduces nutrient supply to the ecosystem up to 69%, a greater effect than body-size-selective or non-selective harvest. These show that behavior at the scale of the individual can have crucial repercussions for the functioning of an entire ecosystem. A fundamental challenge for conservation and management of ecosystem services is improving our ability to predict the impact of populations for ecosystems. Our study suggests that conservation efforts may need to consider other dimensions of biodiversity - such as the individual, if the conservation and management of ecosystem function is a primary goal.