Cannibalism facilitates the use of a novel environment in the flour beetle, Tribolium castaneum

Abstract

Cannibalism is well known to a ect both the population dynamics and the competitive relationships of organisms. Cannibalistic behaviour commonly increases in stressful conditions, such as when density is high or food is scarce, and cannibals often obtain a nutritional bene®t. Might cannibalism also increase in a novel environment to which a population is poorly adapted physiologically? Moreover, might cannibalistic behaviour provide enough of a nutritional advantage in a nutritionally stressful environment to rescue individuals from its adverse e ects and thus permit colonization and range expansion? Previous work has shown that oat¯our is a particularly stressful environment for Tribolium castaneum. In the study reported here, egg cannibalism by two strains of T. castaneum was signi®cantly enhanced in oat¯our, and egg eating rescued larvae from the adverse demographic e ects of this poor environment. Development time of the cannibals was accelerated almost to the level seen for individuals reared in the nutritionally superior environment (wheat plus brewer's yeast). Their survival and fecundity also increased relative to individuals reared in oat¯our without the opportunity to cannibalize. A sib analysis revealed that for larvae reared in the presence of victim eggs, the extent of cannibalism was genetically variable, so that this trait could evolve, given a selective bene®t exceeding its cost. These results suggest that colonization of a marginal new environment could be facilitated by enhanced rates of cannibalism. The possible interplay between cannibalism and physiological adaptation to a new environment is discussed.Keywords: colonization, ecological genetics, evolution, insects, quantitative genetics, resource use. IntroductionCannibalism occurs in a wide range of organisms and is thought to be a common feature of many life cycles (Fox, 1975; Polis, 1981). The ecological e ects of cannibalism are clear. Predation on conspeci®cs can signi®cantly a ect population size and age structure, and it is often implicated as a mechanism of population regulation (Park et al., 1965; Lloyd, 1968; Van Buskirk, 1989; Fincke, 1994; Wagner & Wise, 1996). Cannibalism can alter competitive relationships both by eliminating competitors and by providing the cannibal with nutritional bene®ts (Fox, 1975; Johansson, 1992; Fincke, 1994). The nutritional bene®t of cannibalism need not be large for the behaviour to evolve: even a small decrease in the development time of the cannibal in a species with overlapping generations may provide enough of a selective advantage to cause the spread of cannibalism, even of full-sibs (Eickwort, 1973).Evidence that cannibalism is nutritionally bene®cial has come both from direct observations of improved survival, development time or fecundity of cannibals (Ho & Dawson, 1966; Fox, 1975; Sonleitner & Guthrie, 1991; Spence & Carcamo, 1991; Agarwala & Dixon, 1992; Tschinkel, 1993), and from the observation that cannibalism often increases when alternative food is scarce (Fox, 1975; Polis, 1981; N...

Oviposition strategy of Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) in relation to conspecific infestation

“…Either the Sitophilus female should (1) attempt to reduce individual competition faced by its offspring by killing eggs that are already present (ovicidal strategy), or (2) a larva within a grain should destroy other larvae (attack strategy) to maximise its expected fitness (Smith and Lessells, 1985). Regarding weevil behaviour, the hypothesis of the attack strategy is supported by the fact that larval cannibalism, which is known to enhance adult fecundity and generate nutritional benefit (Alabi et al, 2008;Alabi et al, 2009;Alabi, 2010;Via, 1999), seems to be controlled genetically (Stevens, 1989). However, there are no published estimates of ovicide and larvicide in Sitophilus species.…”

Comportement de ponte et stratégie reproductive de Sitophilus zeamais [Coleoptera : Curculionidae]

“…(Giga et Smith 1985), une hypothèse adaptative liée à cette stratégie d'acquisition des ressources chez S. zeamais pourrait être émise. La compétition larvaire au niveau des grains peut être avantageuse pour la ou les larves survivantes; elles bénéficieraient ainsi d'un apport énergétique et génétique qui augmente le taux d'accroissement des adultes issus de la compétition (Smith et Lessells 1985;Stevens 1989;Via 1999). Ho et Dawson (1966) ont montré que chez les Tribolium spp.…”

Insecticidal effects of Moroccan plant extracts on development, energy reserves and enzymatic activities of Plodia interpunctella

“…Interestingly, cannibalistic behaviour was observed in starved larvae and in larvae exposed to plant extracts, especially C. erythreae and R. officinalis. Cannibalism is a common phenomenon in many species of insects (Polis, 1998) that increases in stressful conditions, such as when density of populations is high or food is scarce (Via, 1999). Accordingly, the insecticidal effects of plant extracts on P. interpunctella larvae appear to provoke increased cannibalism in comparison with larvae reared on control diet.…”