Stable isotopes as markers to investigate host use by Rhyzopertha dominica
2007
Mahroof, Rizana M. | Phillips, Thomas W.
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.
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