Braconid Wasp (Hymenoptera: Braconidae) Diversity in Forest Plots Under Different Silvicultural Methods

Abstract

Braconid wasps were used as an indicator group to test the hypothesis that the degree of disturbance in silvicultural treatments will change the total abundance and composition of species. Wasps were collected with Malaise traps on undisturbed (control), moderately disturbed (pine single-tree selection) and highly disturbed (pine-hardwood seed-tree) research plots of the USDA Forest Service in the Ouachita National Forest of Western Arkansas. We used 3 measures of wasp diversity: (1) numbers of individuals and numbers of species, (2) estimated total species richness and abundance, and (3) observed and estimated complementarity (proportions of species shared or not shared) among treatment types. In all, 1,300 wasps were collected, representing 23 subfamilies, 84 genera, and 251 morphospecies. Raw numbers of individuals and species suggested little difference among treatments. Total species richness estimates projected that the disturbed treatments have twice the number of species as the undisturbed. However, measures of complementarity revealed strongly different species complexes between treatments: undisturbed and highly disturbed treatments had just 24% of their species in common, whereas moderately and highly disturbed treatments shared 42%. Thus, some species in undisturbed forests are lost after disturbance, even though actual diversity appears to increase. Braconid wasps show promise as sensitive indicators of faunal changes during disturbance. These changes are best perceived through species comparisons between treatments when patterns of relative abundance and faunal complementarity are incorporated.