Predators Lack Complementarity in a Degraded Stream

Abstract

Anthropogenic disturbance has led to the loss of biodiversity, altering ecosystem processes and decreasing stability. Top predators have been disproportionately affected by this degradation. Functional complementarity via niche overlap is one mechanism by which ecosystem processes may be maintained in the absence of a top predator. Aquatic ecosystems have shown a decline in top predators such as salmonids, but few studies have addressed the functional complementarity of alternative predators. In beaver ponds in the western U.S., Western Tiger Salamanders (Ambystoma mavortium) often become the top aquatic predator in the absence of fish, yet no previous studies have explored their trophic ecology. We evaluated this knowledge gap and used criteria including population size structure, diet, and stable isotope analysis to investigate the functional complementarity of a degradation tolerant species, the Arizona Tiger Salamander (A. m. nebulosum), compared to the native but extirpated salmonid top predator, Col...