Predator-induced morphological shift in the pea aphid

Abstract

Aphids exhibit a polymorphism whereby individual aphids are either winged or unwinged. The winged dispersal morph is mainly responsible for the colonization of new plants and, in many species, is produced in response to adverse environmental conditions. Aphids are attacked by a wide range of specialized predators and predation has been shown to strongly in£uence the growth and persistence of aphid colonies. In two experiments, we reared two clones of pea aphid (Acyrthosiphon pisum) in the presence and absence of predatory ladybirds (Coccinella septempunctata or Adalia bipunctata). In both experiments, the presence of a predator enhanced the proportion of winged morphs among the o¡spring produced by the aphids. The aphid clones di¡ered in their reaction to the presence of a ladybird, suggesting the presence of genetic variation for this trait. A treatment that simulated disturbance caused by predators did not enhance winged o¡spring production. The experiments indicate that aphids respond to the presence of a predator by producing the dispersal morph which can escape by £ight to colonize other plants. In contrast to previous examples of predator-induced defence this shift in prey morphology does not lead to better protection against predator attack, but enables aphids to leave plants when mortality risks are high.

Notonectaexhibit threat-sensitive, predator-induced dispersal

“…Evidence that predators have indirect effects that operate at the regional scale through prey habitat selection (Resetarits & Binckley 2009) and by driving prey dispersal (Weisser et al 1999;Hakkarainen et al 2001;Cronin et al 2004; this study) is accumulating. Evidence of indirect effects operating at a metacommunity scale suggest that understanding community structure requires a broader view of species interactions that encompasses interactions operating across habitats, even when one member of the interacting pair is restricted to only one habitat.…”

“…Only a few studies have found that predators affect movement among habitats across a discontinuous landscape, and none of these is in aquatic habitats. For example, predation risk from ladybirds increases the production of dispersal morphs in pea aphids (Acyrthosiphon pisum; Weisser et al 1999), and in a few cases, predator presence in a patch results in emigration from that patch (Hakkarainen et al 2001;Cronin et al 2004). In these cases, risk was considered as a binary effect, predators were either present or absent, rather than a continuous variable, despite evidence that the effect of predators on movement within a habitat can be sensitive to the level of predation risk an individual experiences (e.g.…”

Evolution of transgenerational immunity in invertebrates

“…that there is low cross-immunity), mothers are expected to invest more in the immune protection of the philopatric, non-dispersing morph, than on the dispersing one. This prediction could be tested in insects producing both apterous and winged (alate) forms, such as aphids [51][52][53], ants [54,55], and termites [56], or in species that exhibit a sex-biased dispersal, such as gypsy moths [57] and midges [57]. In each of these cases, the philopatric morph or sex is expected to accrue greater benefits from a higher maternal investment in immunity than the dispersing one.…”

Diapause incidence in the two-spotted spider mite increases due to predator presence, not due to selective predation

“…Thus, the results do not provide compelling evidence for the idea that removal and/or injury of the prey act as a cue. Weisser et al (1999), who found that presence of predators had a stimulatory effect on winged offspring production in pea aphids, also did not find an effect of simulated disturbances. Of course, simulated disturbances differ in many ways from disturbances caused by actual predators.…”

“…Predatory ladybirds (Coccinella septempunctata and Adalia bipunctata) induce a shift from unwinged to winged morphs in the pea aphid, Acyrthosiphon pisum (Dixon and Agarwala 1999;Weisser et al 1999). The winged morph is produced in response to adverse environmental conditions (Dixon 1998), but may also facilitate escape from predation, because ladybirds do not eradicate aphid populations in one aphid generation, and neither in one ladybird generation.…”