Behavioural responses of pine weevils to non‐consumptive interactions with red wood ants

Abstract

Non-consumptive effects are increasingly recognized as important in predator-herbivore interactions, with both fundamental and practical implications. Notably, feeding damage to conifer seedlings by pine weevils, Hylobius abietis (L.), which are serious pests in forest regeneration areas, can be decreased by interactions with ants (Formicidae). To probe the behavioural mechanisms underlying such effects, which have rarely been described in predator-herbivore systems, we investigated how the ants influence the weevils' behaviour around planted conifer seedlings in the field. Half of the seedlings were infested with aphids and attended by red wood ants Formica polyctena F€ orster, whereas the others were used as controls. We asked whether the ants' behaviour towards the weevils differs between these treatments, and whether the weevils' movement behaviour (locomotion, stationary activity and digging) is affected by the treatments and physical interactions with ants. The ants attacked pine weevils more frequently and for longer periods around antattended seedlings than around controls. Weevils' locomotion behaviour also increased markedly when attacked by ants. This may increase the likelihood of pine weevils moving away from, and causing less damage to, ant-attended seedlings. This study demonstrates how non-consumptive effects can be explained in terms of a herbivore's responses to a predator's aggressive behaviours.

Testing associational resistance against pine weevils mediated by Lasius ants attending conifer seedlings

“…In a recent study, it was also shown that ants attacked pine weevils more frequently and for longer periods around ant‐attended seedlings and the locomotion behaviour of pine weevils increased when attacked by red wood ants, suggesting that weevils are more likely to move away from ant‐attended seedlings (Maňák et al. ). The results of the current study support this hypothesis by showing that the presence of ants reduces the number of pine weevils on the seedlings without any weevils being killed, for example by non‐consumptive interactions.…”

“…In a related study, we found that the locomotion behaviour of pine weevils increased during ant attacks, suggesting that behaviourally mediated effects play an important role in ant–plant protection against pine weevils (Maňák et al. ).…”

The Red Wood AntFormica aquilonia(Hymenoptera : Formicidae) May Affect Both Local Species Richness and Composition at Multiple Trophic Levels in a Boreal Forest Ecosystem

“…The red wood ants, Formica (Formica) sensu lato are abundant in European forests, and their stable and high population levels make the ants a very important component of the forest ecosystem (Gößwald 1989(Gößwald -1990, Domisch et al 2005, 2009, Sorvari & Hakkarainen 2005, Ohashi et al 2007, Finér et al 2013. In boreal forests, ants are thought to regulate other invertebrates, including pest species, and protect other groups of insects such as aphids against parasites and predators (Moya-Laraño & Wise 2007, Johansson & Gibb 2012, Maňák et al 2016.…”