Restructuring of Lepidoptera communities by introduced Vespula wasps in a New Zealand beech forest

Publication Type:Journal Article
Year of Publication:1999
Authors:J. R. Beggs, Rees J. S.
Journal:Oecologia
Volume:119
Pagination:565 - 571
Date Published:1999///
ISBN Number:0029-8549
Keywords:ABUNDANCE, BRACKEN, COMMUNITIES, COMMUNITY, DAMAGE, ecological impact, EXTRAFLORAL NECTARIES, HYMENOPTERA, INSECTS, larvae, LEPIDOPTERA, MORTALITY, phenology, POPULATIONS, predation, PREY, shared predator, SPHECOPHAGA-VESPARUM-VESPARUM, VESPIDAE, Vespula, VULGARIS, ZEALAND BEECH FOREST
Abstract:

Introduced social wasps (Vespula vulgaris) reach high densities in some New Zealand beech forests, because honeydew provides an abundant high-energy food source. We manipulated wasp density to estimate an "ecological damage threshold" for large, free- living Lepidoptera larvae. There will be a continuum of ecological damage thresholds for wasp density depending on the prey species or habitat. Experimentally placed small caterpillars had a significantly higher survival rate than large caterpillars, and the survival rate of both groups decreased with increasing wasp density. Spring-occurring caterpillars have a probability of surviving of 0.90-0.95, assuming wasps are the only source of mortality. However, at the peak of the wasp season we predict caterpillars would have virtually no chance (probability of 10(-78) to 10(-40)) of surviving to adults. Wasp abundance must be reduced by at least 88% to conserve the more vulnerable species of free-living caterpillars at wasp densities similar to those observed in our study sites. This equates to a damage threshold of 2.7 wasps per Malaise trap per day. It was exceeded for about 5 months of the year in non-poisoned sites. There are currently no biological or chemical control techniques available in New Zealand that will reduce wasp abundance below this damage threshold throughout the year. Our models show that most Lepidoptera with spring caterpillars will be able to persist, but species with caterpillars occurring in the peak wasp season will be eliminated

URL:ISI:000081128300012
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith