Molecular field analysis of trophic relationships in soil‐dwelling invertebrates to identify mercury, lead and cadmium transmission through forest ecosystems

Abstract

Contamination pathways in complex food chains in soil ecosystems can be difficult to elucidate. Molecular analysis of predator gut content can, however, rapidly reveal previously unidentified trophic interactions between invertebrates and thereby uncover pathways of pollutant spread. Here, we measured concentrations of the toxic metals lead, cadmium and mercury in carabid beetle predators and their prey. Invertebrates were sampled at one control and four heavy metal-polluted sites to reveal the impact of diet composition and seasonal variation in prey availability on metal burden in carabids and metal transfer pathways through forest ecosystems. This is the first report, to our knowledge, of carabid diet composition based on PCR analysis of gut contents at the forest community level, rather than in cultivated fields. Extensive screening using group- and species-specific primers revealed that carabids ate primarily earthworms and slugs, as well as smaller numbers of woodlice and springtails. Metal concentrations in carabids correlated with seasonal changes in diet. Mercury accumulated in beetle predators more than in their slug prey. As earthworms, slugs and carabid beetles are the major prey of many birds and mammals, prey-predator transfer and associated toxicity are major risks at mercury-contaminated sites. Carabids may be useful bioindicators for assessing the impact of pollutants on soil ecosystems, as long as species and seasonal factors are taken into account.

Editorial 2015

“…; Šerić Jelaska et al . ). Also, qPCR can be used to estimate the quantity of prey DNA (Eitzinger et al .…”

“…), tracking heavy metals through the environment Šerić Jelaska et al . (), estimating the intensity of competition between predator species (Raso et al . ), determining the identity of both host and parasite from empty insect eggs (Gariepy et al .…”

A tale of two fluids: does storing specimens together in liquid preservative causeDNAcross‐contamination in molecular gut‐content studies?

“…Molecular-based gut-content analyses are now widely used to study food webs (e.g., Hagler & Blackmer, 2013;Jelaska et al, 2014;Lundgren & Fergen, 2014;Raso et al, 2014;Schmidt et al, 2014). These techniques detect trophic interactions and facilitate the screening of hundreds or thousands of specimens in a short period of time.…”

Special issue on molecular detection of trophic interactions: Unpicking the tangled bank

“…; Šerić Jelaska et al . ). Some studies are concerned with analysing the range of predators attacking a single target species (e.g.…”