Molecular Elucidation of Carabid Beetle Foraging Behavior in Alfalfa

Global trade facilitates the intercontinental movement of cargo and thus the potential introduction of exotic gastropods continues to increase. Hence, there is a growing need to understand ecological interactions of newly introduced species with the native fauna and exotic gastropods are of particular concern because they pose economic risks to many crops in Kentucky, including alfalfa, soybean, wheat and corn. Within these agroecosystems, generalist predators have been shown to feed on mollusks and, in some countries, regulate their populations. It is therefore essential to examine the mechanisms of predation, decipher the strength of interaction pathways and evaluate the role of predators in biological control. Molecular analysis of predation relies on the extraction of prey DNA from gut samples and, in Kentucky alfalfa, extensive sampling of carabid beetle populations was undertaken to elucidate the strength of these trophic pathways. In 2008, over 1,500 ground beetles (dominated by Harpalus pennsylvanicus) were collected and screened by polymerase chain reaction to identify the presence (or absence) of invasive slug DNA. The DNA of slugs was detectable in predator guts for approximately 12 h, indicating the suitability of this approach for food-web studies. The screening of field-collected specimens identified highly significant levels of trophic connection between ground beetles and invasive slugs in the field. Ultimately, this research has enhanced our understanding of the complex, and often coupled, dynamic interactions between predators and their invasive prey, and provides valuable information for the use of carabid beetles in the management of invasive pests in Kentucky