Chronic effects of an invasive species on an animal community

J. Sean Doody, David Rhind, Brian Green, Christina Castellano, Colin McHenry, Simon Clulow

    Research output: Contribution to journalArticle

    10 Citations (Scopus)

    Abstract

    Invasive species can trigger trophic cascades in animal communities, but published cases involving their removal of top predators are extremely rare. An exception is the invasive cane toad (Rhinella marina) in Australia, which has caused severe population declines in monitor lizards, triggering trophic cascades that facilitated dramatic and sometimes unexpected increases in several prey of the predators, including smaller lizards, snakes, turtles, crocodiles, and birds. Persistence of isolated populations of these predators with a decades-long sympatry with toads suggests the possibility of recovery, but alternative explanations are possible. Confirming predator recovery requires longer-term study of populations with both baseline and immediate post-invasion densities. Previously, we quantified short-term impacts of invasive cane toads on animal communities over seven years at two sites in tropical Australia. Herein, we test the hypothesis that predators have begun to recover by repeating the study 12 yr after the initial toad invasion. The three predatory lizards that experienced 71–97% declines in the short-term study showed no sign of recovery, and indeed a worse fate: two of the three species were no longer detectable in 630 km of river surveys, suggesting local extirpation. Two mesopredators that had increased markedly in the short term due to these predator losses showed diverse responses in the medium term; a small lizard species increased by ~500%, while populations of a snake species showed little change. Our results indicate a system still in ecological turmoil, having not yet reached a “new equilibrium” more than a decade after the initial invasion; predator losses due to this toxic invasive species, and thus downstream effects, were not transient. Given that cane toads have proven too prolific to eradicate or control, we suggest that recovery of impacted predators must occur unassisted by evolutionary means: dispersal into extinction sites from surviving populations with alleles for toxin resistance or toad avoidance. Evolution and subsequent dispersal may be the only solution for a number of species or communities affected by invasive species for which control is either prohibitively expensive, or not possible.

    Original languageEnglish
    Pages (from-to)2093-2101
    Number of pages9
    JournalEcology
    Volume98
    Issue number8
    DOIs
    Publication statusPublished - 1 Aug 2017

    Fingerprint

    animal community
    invasive species
    long term effects
    toad
    predator
    predators
    Bufo marinus
    lizard
    lizards
    toads
    trophic cascade
    snake
    snakes
    crocodiles
    effect
    sympatry
    isolated population
    population decline
    marina
    turtle

    Cite this

    Doody, J. S., Rhind, D., Green, B., Castellano, C., McHenry, C., & Clulow, S. (2017). Chronic effects of an invasive species on an animal community. Ecology, 98(8), 2093-2101. https://doi.org/10.1002/ecy.1889
    Doody, J. Sean ; Rhind, David ; Green, Brian ; Castellano, Christina ; McHenry, Colin ; Clulow, Simon. / Chronic effects of an invasive species on an animal community. In: Ecology. 2017 ; Vol. 98, No. 8. pp. 2093-2101.
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    abstract = "Invasive species can trigger trophic cascades in animal communities, but published cases involving their removal of top predators are extremely rare. An exception is the invasive cane toad (Rhinella marina) in Australia, which has caused severe population declines in monitor lizards, triggering trophic cascades that facilitated dramatic and sometimes unexpected increases in several prey of the predators, including smaller lizards, snakes, turtles, crocodiles, and birds. Persistence of isolated populations of these predators with a decades-long sympatry with toads suggests the possibility of recovery, but alternative explanations are possible. Confirming predator recovery requires longer-term study of populations with both baseline and immediate post-invasion densities. Previously, we quantified short-term impacts of invasive cane toads on animal communities over seven years at two sites in tropical Australia. Herein, we test the hypothesis that predators have begun to recover by repeating the study 12 yr after the initial toad invasion. The three predatory lizards that experienced 71–97{\%} declines in the short-term study showed no sign of recovery, and indeed a worse fate: two of the three species were no longer detectable in 630 km of river surveys, suggesting local extirpation. Two mesopredators that had increased markedly in the short term due to these predator losses showed diverse responses in the medium term; a small lizard species increased by ~500{\%}, while populations of a snake species showed little change. Our results indicate a system still in ecological turmoil, having not yet reached a “new equilibrium” more than a decade after the initial invasion; predator losses due to this toxic invasive species, and thus downstream effects, were not transient. Given that cane toads have proven too prolific to eradicate or control, we suggest that recovery of impacted predators must occur unassisted by evolutionary means: dispersal into extinction sites from surviving populations with alleles for toxin resistance or toad avoidance. Evolution and subsequent dispersal may be the only solution for a number of species or communities affected by invasive species for which control is either prohibitively expensive, or not possible.",
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    Doody, JS, Rhind, D, Green, B, Castellano, C, McHenry, C & Clulow, S 2017, 'Chronic effects of an invasive species on an animal community', Ecology, vol. 98, no. 8, pp. 2093-2101. https://doi.org/10.1002/ecy.1889

    Chronic effects of an invasive species on an animal community. / Doody, J. Sean; Rhind, David; Green, Brian; Castellano, Christina; McHenry, Colin; Clulow, Simon.

    In: Ecology, Vol. 98, No. 8, 01.08.2017, p. 2093-2101.

    Research output: Contribution to journalArticle

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    Doody JS, Rhind D, Green B, Castellano C, McHenry C, Clulow S. Chronic effects of an invasive species on an animal community. Ecology. 2017 Aug 1;98(8):2093-2101. https://doi.org/10.1002/ecy.1889