Intraguild Predation Diminished in Complex-Structured Vegetation: Implications for Prey Suppression

Abstract

Multiple-predator limitation of prey populations may be mediated by both predator-predator interactions and vegetation structure. Antagonistic interactions among predators, such as intraguild predation, can diminish the collective impact of natural enemies on prey population size. However, structurally complex vegetation may moderate such interactions by providing a refuge for predators, thereby enhancing prey suppression. Specifically, we examined the combined impact of two salt-marsh-inhabiting invertebrate predators, the mirid Tytthus vagus and the wolf spider Pardosa littoralis, on suppression of their shared prey, the planthopper Prokelisia dolus, in simple (thatch-free) and complex (thatch-rich) vegetation.In structurally simple habitats in the laboratory, the predators interacted antagonistically, due to the intraguild predation of mirids by spiders, and predation pressure on the planthopper population was relaxed. However, structurally complex habitats dampened this antagonistic interaction by providing a refuge for mirids from spider predation, thereby increasing the combined effectiveness of these predators in suppressing planthopper populations. Consistent with our laboratory results, we found enhanced co-occurrence of these predators in complex habitats in the field, where mirids are apparently at lower risk from spider predation and outbreaks of planthoppers are less likely. In contrast, in simple habitats, mirids were relatively less abundant, a finding consistent with the expectation of increased intraguild predation from spiders. Therefore, in this salt marsh system, complex vegetation diminished the occurrence of intraguild predation between mirids and spiders and increased overall enemy impact on their shared herbivore prey, demonstrating for the first time that plants can mediate enemy effects on insect herbivores by influencing predator-predator interactions.

Complex interactions among mammalian carnivores in Australia, and their implications for wildlife management

“…It is possible that foxes tolerate dingoes more readily in densely vegetated forest areas, such as those studied by Catling & Burt (1995), because of the greater ease of avoidance or evasion once detected where structural refugia are available (e.g. Finke & Denno, 2002).…”

Influences de la sylviculture sur le risque de dégâts biotiques et abiotiques dans les peuplements forestiers

“…The longevity is significantly increased in parasitoids of Rhyacionia buoliana (Syme, 1975) or Ips typographus (Hougardy and Grégoire, 2000) when the wasps are exposed to nectariferous flowers commonly found in conifer stands. Because they are structurally more complex, mixed forests also offer more shelters from adverse conditions to natural enemies (Finke and Denno, 2002) and more nesting sites to insectivorous birds (Barbaro et al, 2007;Dickson, 1979). Finally, it has been suggested that mixtures of tree species would better accommodate antagonistic fungi that slow the spread of fungal pathogens such as H. annosum (Fedorov and Poleschuk, 1981;Johanson and Marklund, 2008) and Phytophthora cinnamomi (Murray, 1987).…”

Critical patch sizes for food‐web modules

“…Because the dominant arthropod predator on the marsh, Pardosa littoralis (Do¨bel et al 1990), is also an intraguild predator (Finke and Denno 2002), we investigated whether the ratio of predators to prey in the S. patens food web varied with patch size and connectivity, and whether these spiders might influence the distribution on the marsh of two potential prey, the mesopredator Tytthus alboornatus, and the herbivore Tumidagena minuta. Using density data (individuals per square meter of sampled S. patens) from the repeated surveys, we calculated the predator-to-prey ratios between Pardosa and Tytthus, Tytthus and Tumidagena, and Pardosa and Tumidagena.…”