Sampling Native Wasps Along Both Vertical and Horizontal Gradients in the Maine Lowbush Blueberry Landscape

Abstract

Native wasps were sampled from 33 lowbush blueberry (Vaccinium angustifolium) fields and adjacent forests in eastern Maine during the summers of 1997 and 1998. Sampling was conducted along a horizontal transect that bisected the field/forest interface using two methods: window-pane traps suspended at varying heights (1, 7, and 14 m above the ground) and ground-level malaise traps. The objectives of this study were to assess (1) the spatial distributions of wasp species assemblages associated with the two distinct habitats and (2) the potential interactions of wasp species assemblages across the blueberry/forest landscape. Wasp samples from the two trap types collected different wasp species assemblages, each of which were consistent across the 2 yr. Both methods documented lower abundances of wasps in blueberry fields in comparison with adjacent forests. Window pane traps at varying heights identified statistically significant but remarkably minor differences in height even at the highest traps in the middle of blueberry fields in both years of the study. The malaise traps detected distinct species assemblages whose horizontal distributions differed substantially from each other. Distributions ranged from those that were trapped exclusively in the forest, through those that were evenly distributed across the landscape, to taxa that were almost exclusively found in the blueberry field centers. Our results suggest that forest and edge habitats may be important refugia for wasp species assemblages that contribute to regulation of blueberry insect pest populations. Detailed knowledge of specific taxa should assist in the management of the blueberry/forest landscape for the conservation and enhancement of beneficial insects.