Stable isotopes as markers to investigate host use by Rhyzopertha dominica

Abstract

Abstract Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) is a serious worldwide pest of stored cereal grains that also has the ability to breed in non‐agricultural host plant material. Stable isotope signatures (concentrations of isotopes) were used as internal tissue markers to determine dietary differences among adult R. dominica and to make inferences about source habitats of field‐trapped insects. Adult R. dominica collected near granaries or from non‐agricultural forested sites near Stillwater, OK, USA, and insects reared on selected hosts under laboratory conditions were studied to determine the carbon and nitrogen isotope signatures. Laboratory‐reared R. dominica showed δ13C (stable isotope ratio of carbon) values similar to the host on which they developed with an enrichment of about 1 in the insect body. Insects reared on seeds of wheat and oak, which have C3 photosynthetic pathways, showed much depleted δ13C values (–23.7 and –26.2, respectively) in comparison to insects reared on seeds of corn, a C4 photosynthetic plant (–11.3). A majority of the field‐collected R. dominica showed δ13C values similar to expectations for a C3 host. However, a few field‐collected insects had δ13C signatures similar to the C4 plant‐reared insects in the laboratory experiment. Stored grain of C4 crops were lacking at many of the sample field sites. These results suggest that R. dominica occurs on either C3‐ or C4‐based hosts in the field, and point to utilization of non‐grain C4 plants as hosts. Our studies indicated that 13C isotope is a reliable marker to infer types of hosts used in the feeding history of R. dominica.