Niche partitioning is often invoked as an explanation for the maintenance of species diversity. Evidence of niche partitioning most often comes in the form of showing ecological differences among taxa. Whether these differences actually promote species coexistence, which allows unequal competitors to remain in systems, is still unclear. Here, we used experimental and observational studies to test for niche partitioning among sympatric damselfly species.

Results/Conclusions

Field experiments in which we manipulated both intra- and interspecific density demonstrate that one genus of damselfly has greater per capita growth rates than two other genera it is frequently sympatric with, which could lead to competitive exclusion. However, these experiments also show that per capita growth rates of each genus are negatively density-dependent and are only limited by increases in intra- not interspecific densities—a demographic signature of niche partitioning. Such niche partitioning should prevent competitive exclusion and maintain each genus in this system. Observational studies across 40 lakes also showed that relative abundances of each genus covaried differently along an environmental gradient of lake abiotic and biotic features, consistent with niche partitioning. Our study emphasizes the importance of actually determining whether ecological differentiation among species is sufficient to maintain species diversity through niche partitioning.