title: Interspecific competition between two generalist parasitoids that attack the leafroller Epiphyas postvittana (Lepidoptera: Tortricidae).
abstract: Two generalist parasitoids, Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) and Therophilus unimaculatus (Turner) (Hymenoptera: Braconidae) attack early instars of tortricid moths, including the light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae). The two parasitoids co-exist in natural habitats, while D. tasmanica is dominant in vineyards, whereas T. unimaculatus occurs mainly in adjacent native vegetation. This difference suggests possible competition between the two species, mediated by habitat. Here, we report on the extent of interspecific differences in host discrimination and the outcome of interspecific competition between the two parasitoids. The parasitoids did not show different behavioural responses to un-parasitized hosts or those that were parasitized by the other species. Larvae of D. tasmanica out-competed those of T. unimaculatus, irrespective of the order or interval between attacks by the two species. The host larvae that were attacked by two parasitoids died more frequently before a parasitoid completed its larval development than those that were attacked by a single parasitoid. Dissection of host larvae parasitized by both species indicated that first instars of D. tasmanica attacked and killed larval T. unimaculatus.
authors.affiliation: School of Agriculture, Food and Wine, University of Adelaide,Adelaide,SA 5005,Australia.
authors.forename: Y
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Bio-Protection Research Centre,Lincoln University,PO Box 85084,Lincoln 7647,New Zealand.
authors.forename: S
authors.initials: S
authors.lastname: Wratten
authors.affiliation: School of the Environment, Flinders University,PO Box 2100 Adelaide,SA 5001,Australia.
authors.forename: H
authors.initials: H
authors.lastname: Sandhu
authors.affiliation: School of Agriculture, Food and Wine, University of Adelaide,Adelaide,SA 5005,Australia.
authors.forename: M
authors.initials: M
authors.lastname: Keller
mesh_terms: D000818:Animals; D003163:Competitive Behavior; D006790:Host-Parasite Interactions; D009036:Moths / Q000469:parasitology*; D013045:Species Specificity; D014863:Wasps / Q000145:classification / Q000502:physiology*
keywords: Dolichogenidea tasmanica; Therophilus unimaculatus; host discrimination; intrinsic competition; light brown apple moth; parasitoid; searching behaviour