Habitat Differences in Resource Density and Distribution Affect Ecology and Life History of a Landscape-Modifying Fish

Abstract

Resource heterogeneity is a widespread phenomenon, as resources are rarely spaced evenly across a landscape. Variation in resource density and distribution can have a myriad of behavioural, ecological, and evolutionary consequences for populations, yet clarifying these effects is still challenging. We combine both novel and previously published data on genetic parentage, relatedness, life history, and predation to present a comprehensive field study of a shell bed in Lake Tanganyika. Here, a wild population of the cichlid fish Neolamprologus multifasciatus is naturally subdivided into habitat regions that differ immensely in shelter density and distribution, as well as in the capacity for the fish to physically rearrange their shelters into clusters (i.e., engage in niche construction). Shelters were evenly, densely, and continuously spaced in one habitat, while they were highly clustered in the other habitat. We expected the environmental potential for polygyny to be greater in the clustered habitat relative to the continuous habitat. Predation regimes and life history traits differed, with N. multifasciatus in the evenly distributed habitat experiencing higher predation threats, earlier maturation, and slower growth than those in the clustered habitat. Metrics of selection, however, were surprisingly consistent between the two habitats, as were patterns of dispersal. Overall, our research leverages the natural subdivision of a wild population into distinct habitats to investigate the ecological and evolutionary implications of resource heterogeneity and habitat modification.