Predation on epigeic, endogeic and anecic earthworms by carabids active in spring and autumn

Abstract

Background and purpose:

Generalist predatory carabid beetles have an important role in controlling the abundance of various prey species within ecosystems, including certain pests. In terms of bio-control, these unspecialised predators may be sustained in the field when pest populations are low by predating on other animals such as earthworms. The aim of this study was to reveal patterns in predation by beetles, represented by the carabid community in the field, on different earthworm species with respect to anecic, endogeic and epigeic earthworm ecotypes.

Materials and methods:

We utilised DNA extracted from the gut content of 23 carabid species to reveal predation on earthworms directly in the field, considering spring and autumn aspects. The extracted DNA from each carabid species collected in the field was then screened using PCR with earthworm species-specific primers.

Results and discussion:

After screening the carabids using five earthworm species-specific primer pairs, 20 species, including 53% of all tested individual beetles, were positive for earthworms, with similar proportions in the spring and autumn samples and between the sexes. Earthworms from all three ecotypes were confirmed within the predator guts and were widely consumed within the carabid community.

Conclusions:

These results suggest that predation on earthworms might be an important mechanism sustaining populations of generalist predatory carabids in the field, which can be advantageous for biological control. Therefore, non-conventional management should be improved to maintain the three ecotypes of the earthworm community as prey for beneficial predatory carabids.

Key words:

Molecular gut content analyses, anecic, endogeic, epigeic earthworms, ecotypes, multiplex PCR, beneficial soil fauna, predatory insects