The significance of facultative scavenging in generalist predator nutrition: detecting decayed prey in the guts of predators using PCR.

摘要: Gut-content analyses using molecular techniques are an effective approach to quantifying predator–prey interactions. Predation is often assumed but scavenging equally likely route by which animal DNA enters the gut of a predator/scavenger. We used PCR (polymerase chain reaction) detect scavenged material in predator homogenates. The rates at decaying slugs (Mollusca: Pulmonata) and aphids (Homoptera: Aphididae) became undetectable were estimated. detectability from both carrion types guts generalist Pterostichus melanarius (Coleoptera: Carabidae) was then determined. effects age weight, as well beetle sex, on detection periods, quantified. Laboratory trials measured prey preference beetles between live prey. Further experiments measured, for first time, feeding P. dead directly field. In field laboratory, preferentially fed if available, changed increasingly decayed. Disappearance slug wheat fields grasslands estimated identified main scavenger. Comparison retention time field, with period predators, showed that PCR-based not able distinguish predated food items. This could potentially lead overestimation impact predation (and other prey) carabids. Possible implications facultative invertebrate predators biocontrol food-web research discussed.