Molecular gut analysis of carabids (Coleoptera: carabidae) using aphid primers

Abstract

Carabid beetles are found in a variety of Montana crops, although their impact on the food web is poorly known. To detect aphidophagy using the polymerase chain reaction (PCR), carabids were fed a single aphid and allowed to digest for increasing time intervals. Aphidspecific PCR primers were used to amplify aphid DNA from carabid beetles. For the laboratory-fed beetles, PCR detection of aphidophagy decreased with longer digestion periods. Further, there were differences among genera in the proportion of fed beetles positive for aphid DNA at the tested digestion intervals. Field surveys of 273 individual carabid beetle gut contents, representing seven genera, found all genera surveyed in Montana cropping systems, except Microlestes and Pasymachus, positive for aphid DNA. Genera positive for aphid DNA were Calosoma, Harpalus, Pterostichus, Amara, Agonum, and Bembidion. The detectability of prey DNA in the context of predator size is discussed.