title: Loss of predator species, not intermediate consumers, triggers rapid and dramatic extinction cascades.
abstract: Ecological networks are tightly interconnected, such that loss of a single species can trigger additional species extinctions. Theory predicts that such secondary extinctions are driven primarily by loss of species from intermediate or basal trophic levels. In contrast, most cases of secondary extinctions from natural systems have been attributed to loss of entire top trophic levels. Here, we show that loss of single predator species in isolation can, irrespective of their identity or the presence of other predators, trigger rapid secondary extinction cascades in natural communities far exceeding those generally predicted by theory. In contrast, we did not find any secondary extinctions caused by intermediate consumer loss. A food web model of our experimental system-a marine rocky shore community-could reproduce these results only when biologically likely and plausible nontrophic interactions, based on competition for space and predator-avoidance behaviour, were included. These findings call for a reassessment of the scale and nature of extinction cascades, particularly the inclusion of nontrophic interactions, in forecasts of the future of biodiversity.
authors.affiliation: Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Ian
authors.identifier: 0000-0002-4698-6448
authors.initials: I
authors.lastname: Donohue
authors.affiliation: Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
authors.forename: Owen L
authors.initials: OL
authors.lastname: Petchey
authors.affiliation: CNRS, IRD, EPHE, CC065, Institut des Sciences de l'Evolution, BioDICée team, Université de Montpellier, Montpellier, France.
authors.forename: Sonia
authors.initials: S
authors.lastname: Kéfi
authors.affiliation: CNRS, IRD, EPHE, CC065, Institut des Sciences de l'Evolution, BioDICée team, Université de Montpellier, Montpellier, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Génin
authors.affiliation: Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Andrew L
authors.identifier: 0000-0001-7334-0434
authors.initials: AL
authors.lastname: Jackson
authors.affiliation: Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Nessa E
authors.initials: NE
authors.lastname: O'Connor
mesh_terms: D000818:Animals; D044822:Biodiversity; D053476:Extinction, Biological; D020387:Food Chain; D005544:Forecasting; D011157:Population Dynamics; D011235:Predatory Behavior
keywords: algae; consumers; ecological stability; field experiment; food web; intertidal; nontrophic interactions; rocky shore; secondary extinctions; structural robustness