Description:
<jats:title>Abstract</jats:title><jats:p>Plant roots represent an important food source for soil‐dwelling animals, but tracking herbivore food choices below‐ground is difficult. Here, we present an optimized <jats:styled-content style="fixed-case">PCR</jats:styled-content> assay for the detection of plant <jats:styled-content style="fixed-case">DNA</jats:styled-content> in the guts of invertebrates, using general plant primers targeting the <jats:italic>trn</jats:italic><jats:styled-content style="fixed-case">T</jats:styled-content>‐<jats:styled-content style="fixed-case">F</jats:styled-content> chloroplast <jats:styled-content style="fixed-case">DNA</jats:styled-content> region. Based on this assay, we assessed the influence of plant identity on the detectability of ingested plant <jats:styled-content style="fixed-case">DNA</jats:styled-content> in <jats:styled-content style="fixed-case"><jats:italic>Agriotes</jats:italic></jats:styled-content> click beetle larvae. Six different plant species were fed to the insects, comprising a grass, a legume and four nonlegume forbs. Moreover, we examined whether it is possible to amplify <jats:styled-content style="fixed-case">DNA</jats:styled-content> of decaying plants and if <jats:styled-content style="fixed-case">DNA</jats:styled-content> of decayed plant food is detectable in the guts of the larvae. <jats:styled-content style="fixed-case">DNA</jats:styled-content> of the ingested roots could be detected in the guts of the larvae for up to 72‐h post‐feeding, the maximum digestion time tested. When fed with living plants, <jats:styled-content style="fixed-case">DNA</jats:styled-content> detection rates differed significantly between the plant species. This may be ascribed to differences in the amount of plant tissue consumed, root palatability, root morphology and/or secondary plant components. These findings indicate that plant identity can affect post‐feeding <jats:styled-content style="fixed-case">DNA</jats:styled-content> detection success, which needs to be considered for the interpretation of molecularly derived feeding rates on plants. Amplification of plant <jats:styled-content style="fixed-case">DNA</jats:styled-content> from decaying plants was possible as long as any tissue could be retrieved from the soil. The consumption of decaying plant tissue could also be verified by our assay, but the insects seemed to prefer fresh roots over decaying plant material.</jats:p>