The conceptual and practical implications of interpreting diet breadth mechanistically in generalist predatory insects

Abstract

The concept of ecological generalism (or polyphagy) is widely used in ecology to describe and predict aspects of the behaviour of predatory insects, notably with regard to the management of insect pests. The assumptions of ecological generalism have their basis in competition and optimization. We review the historical context and perspectives that led to the development of the concept of ecological generalism as it is applied to diet breadth in predatory insects. We identify how flaws in this concept limit its utility in describing and predicting the behaviour of organisms. We re‐analyse the behavioural expectations of putatively generalist organisms with a focus on the mechanistic aspects of predation; that is, we develop an interpretation based on the adaptations that mediate their responses to particular cues in their environment. This mechanistic analysis emphasizes the need to determine the primary environmental associations of putatively generalist species, and the adaptations that underpin those associations. This approach thus highlights the importance of appropriate matching of predator species to prey species in biological control, based on an understanding of these adaptations and associations. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••–••.

Prey range of the predatory ladybird Cryptolaemus montrouzieri

“…To a lesser extent, also eggs of coleopterans and lepidopterans supported survival, larval development and/or reproduction of the ladybird. Whereas there were only scattered reports of the feeding on non-mealybug prey by C. montrouzieri in the literature (Kairo et al 2012;Finlay-Doney and Walter 2012b), the present study compared the effects of non-mealybug prey from different insect orders on the developmental and reproductive performance of the predator. Although we observed a reduced fitness of the predator when offered non-mealybug prey species, our data indicate that it may be able to sustain itself in a crop on alternative prey when mealybugs are absent or mealybug populations are low.…”

“…More recently, mass produced ladybirds are intensively used for augmentation biological control in protected cultivation and interior landscaping (Chong and Oetting 2007;Muştu et al 2008;Hodek and Honȇk 2009;Roy and Migeon 2010). Although C. montrouzieri is mainly released against mealybug pests, it has also been reported to feed on a wide range of other hemipterans in the field, including aphids, scale insects and whiteflies (Malais and Ravensberg 2002;Ś lipiński 2007;Finlay-Doney and Walter 2012b;Kairo et al 2012;Cock 2013). Its potential to develop and reproduce when offered these alternative prey, however, has hardly been investigated (Finlay-Doney and Walter 2012b).…”

“…Although C. montrouzieri is mainly released against mealybug pests, it has also been reported to feed on a wide range of other hemipterans in the field, including aphids, scale insects and whiteflies (Malais and Ravensberg 2002;Ś lipiński 2007;Finlay-Doney and Walter 2012b;Kairo et al 2012;Cock 2013). Its potential to develop and reproduce when offered these alternative prey, however, has hardly been investigated (Finlay-Doney and Walter 2012b).…”

Resident spiders as predators of the recently introduced light brown apple moth,Epiphyas postvittana

“…Their lack of prey specificity and relatively long generation times may limit their ability to regulate pest populations, although these same characteristics may allow them to be present before pest outbreaks occur (Settle et al, 1996;Symondson et al, 2002;Finlay-Doney & Walter, 2012). Their lack of prey specificity and relatively long generation times may limit their ability to regulate pest populations, although these same characteristics may allow them to be present before pest outbreaks occur (Settle et al, 1996;Symondson et al, 2002;Finlay-Doney & Walter, 2012).…”

Functional responses can unify invasion ecology

“…We advocate that current and emerging invaders of concern, such as those identified by national and international regulatory agencies (e.g. new EU Regulation 1143/2014) be tested for functional responses in a standardized way, analogous to tests of target specificity and efficacy of biological control agents (see Fernández-Arhex and Corley 2003;Finlay-Doney and Walter 2012). Indeed, the biological control community has essentially been asking the same question as invasion ecologists for many decades (and indeed using functional and numerical responses) of what are technically beneficial introduced species based on their predicted impact when released into the environment.…”