Population structure of a predatory beetle: the importance of gene flow for intertrophic level interactions.

Migration and gene flow of natural enemies play an important role in the stability of predator-prey interactions and community organization in both natural and managed systems. Yet, relative to that of their herbivorous insect prey, the genetic structure of natural enemy populations has been little studied. We present evidence that populations of the predatory coccinellid beetle Coleomegilla maculata (Coleoptera: Coccinellidae), are not genetically subdivided and that levels of gene flow among these populations are extremely high. Furthermore, in the same geographical area, gene flow of C. maculata was significantly (one order of magnitude) greater than that of an abundant prey species, the Colorado potato beetle Leptinotarsa decemlineata (Coleoptera: Chrysomelidae). The high mobility of this natural enemy relative to the insect herbivores on which it feeds may contribute to its effectiveness as a biological control agent in agricultural systems.