Nonlinear effect of density on trophic niche width and between‐individual variation in diet in a neotropical cichlid

Abstract

AbstractDensity‐dependent dynamics have considerable effects in many ecological processes and patterns that characterize natural populations. In the present study, we aim at evaluating the effect of density on the diet width and between‐individual variability in nine different pike cichlid Crenicichla lepidota populations dwelling in floodplain lagoons. Our results indicated that low‐density populations exhibit small diet breadth as well as small between‐individual variability in their diet. In addition, these populations were characterized by a nested diet pattern, where the diet of specialist individuals represented a subset of the food items consumed by generalist individuals. Populations with intermediate densities had a larger populational diet breadth while the individual diet breadth remained unchanged. This pattern was due to an increase in between‐individual variability in diet, which consequently decreases the diet overlap among individuals and thus lower diet nestedness. Finally, under high densities, the niche width at the population level decreased because of lower between‐individual variability and higher diet overlap. Together, these results showed that niche width exhibits a non‐linear function with density. At first, an increase in density increased the niche width because of greater between‐individual diet variability. However, after a threshold density value, the effect was reversed, and the niche width decreased because of a higher diet overlap among individuals.