Prey DNA detection success following digestion by intraguild predators: Influence of prey and predator species

Intraguild predation (IGP) has been increasingly recognized as an important interaction in ecological systems over the past two decades, and remarkable insights have been gained into its nature and prevalence. We have developed a technique using molecular gut-content analysis to compare the rate of IGP between closely related species of coccinellid beetles (lady beetles or ladybirds), which had been previously known to prey upon one another. We first developed PCR primers for each of four lady beetle species: Harmonia axyridis, Coccinella septempunctata, Coleomegilla maculata and Propylea quatuordecimpunctata. We next determined the prey DNA detection success over time (DS ₅₀) for each combination of interacting species following a meal. We found that DS ₅₀ values varied greatly between predator-prey combinations, ranging from 5.2 to 19.3h. As a result, general patterns of detection times based upon predator or prey species alone are not discernable. We used the DS ₅₀ values to correct field data to demonstrate the importance of compensation for detection times that are specific to particular predator-prey combinations.