title: An exotic parasitoid provides an invasional lifeline for native parasitoids.
abstract: The introduction of an exotic species may alter food webs within the ecosystem and significantly affect the biodiversity of indigenous species at different trophic levels. It has been postulated that recent introduction of the brown marmorated stinkbug (Halyomorpha halys(Stål)) represents an evolutionary trap for native parasitoids, as they acceptH. halysegg masses as a host but produce no viable progeny. Interspecific interactions between European egg parasitoid,Trissolcus cultratus(Mayr), and an Asian parasitoid,Trissolcus japonicus(Ashmead), were assessed by providing egg masses toT. cultratusat various time intervals following the initial parasitization byT. japonicus. The suitability of the host for the parasitoid development was re-assessed by providingT. cultratuswith fresh and frozen egg masses of various ages. The likelihood ofT. cultratusbeing able to attack previously parasitized egg masses was determined by assessing the duration of egg mass guarding behavior byT. japonicusfollowing parasitization. The results of experiments examining the interspecific interactions between a native European egg parasitoid,T. cultratus, and an Asian parasitoid,T. japonicus(a candidate for the biological control ofH. halys), showed that the native species can act as facultative hyperparasitoid of the exotic one. Although this is only possible during certain stages ofT. japonicusdevelopment, the presence of the introduced parasitoid may reduce the impact of the evolutionary trap for indigenous parasitoid species. There is a possibility that the occurrence of facultative hyperparasitism between scelionid parasitoids associated with stinkbugs is common. This resulting intraguild predation could promote conservation and stabilization of natural communities by impacting the diversity and population dynamics of native stinkbugs and their parasitoids (e.g., by allowing native parasitoids to avoid wasting reproductive effort on unsuitable hosts), or reduce success of biological control programs (e.g., by reducing the population size of the exotic parasitoids).
authors.affiliation: Department of Biology Western University London ON Canada; London Research and Development Centre Agriculture and Agri-Food Canada London ON Canada; CABI-Europe Switzerland Delémont Switzerland.
authors.forename: Joanna K
authors.initials: JK
authors.lastname: Konopka
authors.affiliation: CABI-Europe Switzerland Delémont Switzerland.
authors.forename: Tim
authors.initials: T
authors.lastname: Haye
authors.affiliation: London Research and Development Centre Agriculture and Agri-Food Canada London ON Canada.
authors.forename: Tara
authors.initials: T
authors.lastname: Gariepy
authors.affiliation: Ottawa Research and Development Centre Agriculture and Agri-Food Canada Ottawa ON Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Mason
authors.affiliation: Agassiz Research and Development Centre Agriculture and Agri-Food Canada Agassiz BC Canada.
authors.forename: David
authors.initials: D
authors.lastname: Gillespie
authors.affiliation: Department of Biology Western University London ON Canada.
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: McNeil
keywords: biological control; brown marmorated stinkbug; egg parasitoids; evolutionary trap; facultative hyperparasitoid; larval competition