Predators and mutualists influence the exclusion of aphid species from natural communities

Abstract

We investigated why two species of aphids (Aphis jacobaeae and Brachycaudus cardui) were very rare in a study site despite their abundance in the surrounding area. The study site contained many common species of aphid and we tested the hypothesis that the community of aphid predators in the field excluded the missing species. Colonies of the two aphid species were artificially initiated in the experimental site and allocated to one of four treatments: control; ground predator exclusion; total predator exclusion, and provision of mutualist ants. Two measures of colony performance were analysed: longevity and cumulative aphid density. Colonies decline naturally in late summer but control colonies disappeared very quickly while colonies protected from all predators survived the longest. The performance of colonies protected from just ground predators was intermediate. We failed to persuade ants to tend A. jacobaeae. Colonies of B. cardui attended by ants performed better than controls and those with ground predators excluded, but not as well as those with all predators excluded. We conclude that the absence of the two species of aphid in the study site is influenced by the resident predator community, and by the availability of mutualists.

Relative importance of predators and parasitoids for cereal aphid control

“…Flying aphid predators and parasitoids were reduced by setting wire cages over the plots at the end of June. The cages had a mesh size of 8 mm to avoid changes in microclimate and were covered with sticky glue to deter or capture flying arthropods (see Mü ller & Godfray 1999). The bottom edge of the cages was left without glue, and gaps resulting from the uneven soil surface gave ground-dwelling predators access.…”

Multitrophic interactions among plants, aphids, alternate prey and shared natural enemies - a review

“…But clearly even in this case, much remains to learn about the importance and specific mechanisms of indirect effects. It is of much interest, for example, to determine how often a single alternate prey species (e.g., Gilstrap, 1997;Michels & Burd, 2007), versus a diffuse collection of multiple prey species (e.g., Müller & Godfray, 1999b, Ostman, 2004, may critically affect a focal prey species indirectly by interactions with shared predators. In general, we now have the strong experimental foundation to support our ecological intuition that predator-mediated, indirect interactions among aphids and other prey are likely to occur widely, and that they are likely to be multifaceted.…”

“…The pressure exerted by predators on other herbivores may sometimes be associated with a community of aphid species rather than a single, highly abundant species. Müller & Godfray (1999b), for example, tested whether two aphid species that were absent from an Eng-lish meadow [Aphis jacobaeae Schrank and Brachycaudus cardui (L.)] could establish when introduced. Founder colonies of the aphids were placed on their host plant (Senecio jacobaea L.) in the meadow but failed to persist unless the diverse resident community of predators was prevented from attacking them (either mechanically or by aphid-tending ants).…”

The effects of attacks by the mutualistic ant, Lasius japonicus Santschi (Hymenoptera: Formicidae) on the foraging behavior of the two aphidophagous ladybirds, Coccinella septempunctata brucki Mulsant (Coleoptera: Coccinellidae) and Propylea japonica (Thunberg) (Coleoptera: Coccinellidae)

“…Ants protect homopterans from their natural enemies, and this protection is thought to provide important benefits to the population growth of ant-attendant homopterans Whitham, 1989, 1991;Müller and Godfray, 1999;Morales, 2000). For instance, ants negatively affect the abundance of homopteran predators Whitham, 1989, 1991;Dutcher et al, 1999) and prey consumption by aphidophagous insects (Vinson and Scarborough, 1989).…”

“…Ladybirds are thought to be an important predator of aphids because of their abundance and voracity (Obrycki and Kring, 1998;Müller and Godfray, 1999), and are often observed in aphid colonies with mutualistic ants in the fields (e.g. Kaneko, 2002Kaneko, , 2003a.…”