Ecological Entomology (2009) 34, 107-113

Russell H. Messing and Xin-Geng Wang (2009)
Competitor-free space mediates non-target impact of an introduced biological control agent
Ecological Entomology 34 (1), 107-113
Abstract: 1. Enemy-free space has been shown to mediate host shifts in herbivores, but this has not previously been documented in parasitoids. Also, natural enemies shown to maintain host shifts have always been from higher trophic levels, rather than competitors.
2. In Hawaii, an Australian parasitoid (Diachasmimorpha tryoni) of medflies that loses competition contests to a subsequently introduced Asian parasitoid (Fopius arisanus) has shifted its realised host range to attack non-target gall flies on lantana.
3. The present study demonstrates experimentally that D. tryoni reproduction is: (i) lower on medflies in coffee when F. arisanus is present than when it is absent; (ii) higher in gall flies on lantana than on medflies in coffee, when F. arisanus is present; and (iii) higher in medflies on coffee than in gall flies on lantana, when F. arisanus is absent. This meets Berdegue et al. 's (Ecological Entomology, 21, 203-217, 1996) three conditions to confirm the importance of enemy-free space.
4. In the field, F. arisanus is abundant on medflies, whereas D. tryoni is rare on medflies, but is the dominant parasitoid of lantana gall flies.
5. Competitor-free space is thus shown to be a key mechanism maintaining an apparent host shift by an introduced biocontrol agent onto a non-target species.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Xin-Geng Wang

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
environment/habitat manipulation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ceratitis capitata	Coffee (Coffea)	U.S.A. (Hawaii)
Fopius arisanus (parasitoid)	Ceratitis capitata	Coffee (Coffea)	U.S.A. (Hawaii)
Diachasmimorpha tryoni (parasitoid)	Ceratitis capitata	Coffee (Coffea)	U.S.A. (Hawaii)