Detection of facultative intraguild predation events by Monochamus titillator on the southern pine beetle guild using molecular gut analyses

The southern pine beetle guild (SPBG) (Coleoptera: Curculionidae: Scolytinae) is arguably the most destructive group of forest pests in the Southeastern United States. Larvae of the wood borer associate Monochamus titillator (F.) (Coleoptera: Cerambycidae) have been hypothesized to be facultative intraguild predators of the SPBG. In this study we tested the hypothesis that predation on members of the SPBG by M. titillator larvae was detectable under field conditions. We developed species-specific PCR primers to test for each of the 5 species of the SPBG and compared their molecular half-lives under laboratory conditions. Field collected M. titillator larvae were then sampled to determine the frequency of SPBG consumption. The species composition of members of the SPBG in host material was then compared to that detected in the digestive systems of M. titillator larvae. Our results demonstrate that consumption of members of the SPBG is detectable under field conditions, but with a rather low frequency due to the short molecular half-lives of SPBG DNA.