Reciprocal inhibition and competitive hierarchy cause negative
biodiversity-ecosystem function relationships
Abstract
The relationship between biodiversity and ecosystem function (BEF)
captivates ecologists, but the factors responsible for the direction of
this relationship remain unclear. While higher ecosystem functioning at
higher biodiversity levels (‘positive BEF’) is not universal in nature,
negative BEF relationships seem puzzlingly rare. Here, we develop a
dynamical consumer-resource model inspired by microbial decomposer
communities in pitcher plant leaves to investigate BEF. We manipulate
microbial diversity via controlled colonization and measure their
function as total ammonia production. We test how niche partitioning
among bacteria and other ecological processes influence BEF in the
leaves. We find that a negative BEF can emerge from reciprocal
interspecific inhibition in ammonia production causing a negative
complementarity effect, or from competitive hierarchies causing a
negative selection effect. Absent these factors, a positive BEF was the
typical outcome. Our findings provide a potential explanation for the
rarity of negative BEF in empirical data.