Exotic Coccinellid Species Altered the Community Structure and Function of the North American Aphidophagous Coccinellid Assemblages
Several species in the family Coccinellidae provide biological control services against aphid pests in agroecosystems. To maximize naturally occurring biological control, several aphidophagous Coccinellid species have been introduced beyond their native ranges into North America. Since the late 20th century, studies have documented an observable decline in several native Coccinellid species after the introduction of such non-native species. However, less is known about how consistent changes are to community composition, particularly across geographic areas and different habitats. Also unknown is how such changes impact potential biological control capacity of these communities. To examine this question, we collected papers ranging from 1913-2011 that quantified community compositions following the introductions of two primary species, Coccinella septempunctata (Linnaeus) and Harmonia axyridis (Pallas). An ordination approach was used to examine relationships among aphidophagous Coccinellid communities and quantify change to the communities after the introduction of these two non-native species. Our results show that the introduction of H. axyridis and C. septempunctata caused a significant shift in the native coccinellid community composition.This shift was due to the increased dominance of both non-natives across managed and natural systems and the significant declines in several native species. This decline was not consistent across native species, with some such as Hippodamia convergens (Guérin-Méneville) and Coccinella novemnotata (Herbst) showing significant decline and others such as Coleomegilla maculata (De Geer) remaining stable. While individual species changed in abundance, this composition change was not associated with a significant change in the relative biological control capacity of the community.