Ecological effects of an invasive social wasp on Hawaiian Hymenoptera

The introduction of non-native organisms is a leading cause of species imperilment. This study examines the impact of a social wasp invader, Vespula pensylvanica, on two groups of native Hymenoptera: Hylaeus bees and Odynerus wasps, which represent two major insect radiations in Hawaii. Because Hawaii has no native social insects, endemic solitary bees and wasps may be particularly sensitive to predation and competition from yellowjackets. Experimental removal of V. pensylvanica colonies resulted in increased local abundances of endemic solitary Hymenoptera. Analyses of nesting patterns indicate that the presence of yellowjacket colonies in the fall influences the distribution and abundance of solitary wasps in the subsequent spring. We further demonstrate how this invasive yellowjacket influences the composition of local hymenopteran communities through predation and competition for resources.