title: Predators with multiple ontogenetic niche shifts have limited potential for population growth and top-down control of their prey.
abstract: Catastrophic collapses of top predators have revealed trophic cascades and community structuring by top-down control. When populations fail to recover after a collapse, this may indicate alternative stable states in the system. Overfishing has caused several of the most compelling cases of these dynamics, and in particular Atlantic cod stocks exemplify such lack of recovery. Often, competition between prey species and juvenile predators is hypothesized to explain the lack of recovery of predator populations. The predator is then considered to compete with its prey for one resource when small and to subsequently shift to piscivory. Yet predator life history is often more complex than that, including multiple ontogenetic diet shifts. Here we show that no alternative stable states occur when predators in an intermediate life stage feed on an additional resource (exclusive to the predator) before switching to piscivory, because predation and competition between prey and predator do not simultaneously structure community dynamics. We find top-down control by the predator only when there is no feedback from predator foraging on the additional resource. Otherwise, the predator population dynamics are governed by a bottleneck in individual growth occurring in the intermediate life stage. Therefore, additional resources for predators may be beneficial or detrimental for predator population growth and strongly influence the potential for top-down community control.
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The Netherlands. aleeuwen@princeton.edu
authors.forename: Anieke
authors.initials: A
authors.lastname: van Leeuwen
authors.forename: Magnus
authors.initials: M
authors.lastname: Huss
authors.forename: Anna
authors.initials: A
authors.lastname: Gårdmark
authors.forename: Michele
authors.initials: M
authors.lastname: Casini
authors.forename: Francesca
authors.initials: F
authors.lastname: Vitale
authors.forename: Joakim
authors.initials: J
authors.lastname: Hjelm
authors.forename: Lennart
authors.initials: L
authors.lastname: Persson
authors.forename: André M
authors.initials: AM
authors.lastname: de Roos
mesh_terms: D000818:Animals; D017753:Ecosystem; D005399:Fishes / Q000502:physiology*; D020387:Food Chain; D048389:Gadus morhua / Q000502:physiology; D008954:Models, Biological; D011157:Population Dynamics; D011158:Population Growth; D011235:Predatory Behavior