Oecologia (2006) 150, 421-434

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Stephen B. Heard, John O. Stireman III, John D. Nason, Graham H. Cox, Christopher R. Kolacz and Jonathan M. Brown (2006)
On the elusiveness of enemy-free space: spatial, temporal, and host-plant-related variation in parasitoid attack rates on three gallmakers of goldenrods
Oecologia 150 (3), 421-434
Abstract: Host shifting by phytophagous insects may play an important role in generating insect diversity by initiating host-race formation and speciation. Models of the host shifting process often invoke reduced rates of natural enemy attack on a novel host in order to balance the maladaptation expected following the shift. Such 'enemy-free space' has been documented for some insects, at some times and places, but few studies have assessed the occurrence of enemy-free space across years, among sites, or among insect species. We measured parasitoid attack rates on three insect herbivores of two goldenrods (Solidago altissima L. and Solidago gigantea Ait.), with data from multiple sites and multiple years for each herbivore. For each insect herbivore, there were times and sites at which parasitoid attack rates differed strongly and significantly between host plants (that is, enemy-free space existed on one host plant or the other). However, the extent and even the direction of the attack-rate difference varied strongly among sites and even among years at the same site. There was no evidence of consistent enemy-free space for any herbivore on either host plant. Our data suggest that enemy-free space, like many ecological and evolutionary forces, is likely to operate as a geographic and temporal mosaic, and that conceptual models of host shifting that include enemy-free space as a consequence of host novelty are likely too simple.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website

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

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Solidago altissima (weed)
Solidago gigantea (weed)