Abstract
Prey naiveté-the failure of prey to recognize novel predators as threats-is thought to exacerbate the impact that exotic predators exert on prey populations. Prey naiveté varies under the influence of eco-evolutionary mediating factors, such as biogeographic isolation and prey adaptation, although an overall quantification of their influence is lacking. We conducted a global meta-analysis to test the effects of several hypothesized mediating factors on the expression of prey naiveté. Prey were overall naive towards exotic predators in marine and freshwater systems but not in terrestrial systems. Prey naiveté was most pronounced towards exotic predators that did not have native congeneric relatives in the recipient community. Time since introduction was relevant, as prey naiveté declined with the number of generations since introduction; on average, around 200 generations may be required to erode naiveté sufficiently for prey to display antipredator behaviour towards exotic predators. Given that exotic predators are a major cause of extinction, the global predictors and trends of prey naiveté presented here can inform efforts to meet conservation targets.
Highlights
The introduction of exotic species can cause substantial impacts on biodiversity and ecosystems [1,2,3], and such impacts are likely to exacerbate as rates of species introduction continue to increase [4,5]
Naiveté was found to be significantly pronounced in animals from marine and freshwater systems but not significant in terrestrial systems (g = −0.35 ± 0.42, p = 0.107; figure 1a)
Prey naiveté was significant only when the original biogeographic realm of the exotic predator differed from the realm in which it was introduced (g = −0.47 ± 0.20, p < 0.001; figure 1c), but not if the introduction occurred within the same biogeographic realm (g = −0.30 ± 0.42, p = 0.165; figure 1c)
Summary
The introduction of exotic species can cause substantial impacts on biodiversity and ecosystems [1,2,3], and such impacts are likely to exacerbate as rates of species introduction continue to increase [4,5]. The disproportionate impact of exotic predators on native communities is often attributed to prey naiveté—the failure of prey to recognize (or respond appropriately) to a novel predator species and/or the lack of an appropriate defence (sensu [10]). Such prey naiveté towards exotic predators likely derives from insufficient eco-evolutionary exposure [10,11,12,13,14,15,16]. Rat impacts are reduced on islands that possess native rats or functionally similar land crabs, presumably because fauna on those islands are less naive to the effects of introduced omnivores [18]
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