Evaluating the impact of a biological control parasitoid on invasive Vespula wasps in a natural forest ecosystem |
| |
Authors: | JR Beggs JS Rees RJ Toft TE Dennis ND Barlow |
| |
Institution: | aSchool of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand;bLandcare Research, Private Bag 6, Nelson, New Zealand;cAgResearch, P.O. Box 60, Lincoln, New Zealand |
| |
Abstract: | The overall impact of the parasitoid Sphecophaga vesparum vesparum on invasive Vespula wasps in New Zealand native beech forest was evaluated by assessing the levels of parasitism achieved and the parasitoid’s effect at nest level and population level. The maximum proportion of nests parasitised was 17%, but there was no significant increase with time (r2 = 0.139; p = 0.115). However, there was an exponential reduction in the number of parasitoids produced per parasitised nest from a peak of 570 (SE = 143) parasitoids per nest in 1990, declining to only 15 (SE = 6) parasitoids per nest in 2004. Even when parasitoid density was high, the parasitoid had no detectable impact on the number of small cells or the total host nest size, but it halved the number of large (reproductive) cells produced. This may have resulted in fewer queens produced per parasitised nest. Wasp nest density was highly variable from year to year, but there was no evidence that the wasp population density at the parasitised site (Pelorus Bridge) had declined relative to the five sites where the parasitoid had not established. We conclude that the parasitoid is unlikely to have had any significant effect on wasp populations hitherto, nor is it likely to impact host populations in the future. We recommend other biological control programs adopt pre-release assessment of per capita impact as a way of identifying agents that are more likely to be successful and hence minimising economic and potential ecological costs of biocontrol. |
| |
Keywords: | Agent evaluation Biological control Conservation management Efficacy assessment Invasive alien species Pre-release studies Sphecophaga vesparum vesparum Vespula vulgaris |
本文献已被 ScienceDirect 等数据库收录! |
|