Spatial structure of forest lepidopteran communities in oak hickory forests of Indiana

The response of forest insect communities to disturbances such as timber harvest will likely depend on the underlying spatial structure of species assemblages before the disturbance occurs. Unfortunately, many studies of forest management implicitly assume homogeneity of community structure before harvest; postlogging communities are inferred to be a direct product of the imposed management. The goal of this study is to examine variation in the community structure of forest Lepidoptera using the pretimber harvest data on Lepidoptera from 20 forest sites within three watersheds at Morgan Monroe State Forest, IN. A total of 14,537 individuals representing 324 species of Lepidoptera were sampled from Morgan-Monroe State Forest in 2007. Sampling efficiency was not a function of management unit, and, surprisingly, we found little evidence that management units differed in overall community composition. Diversity partitioning suggested that > 99% of Simpson diversity (species dominance) was determined at the local scale, and each site contained the same 10 dominant taxa in rank order. Variation in species richness seemed to be more a problem of sampling bias than underlying differences in habitat preference by moth feeding guilds. Finally, Mantel tests suggested that forest moth communities at Morgan-Monroe are not spatially autocorrelated. The results here are encouraging because they strongly suggest that shifts in lepidopteran community structure should reflect the community response to disturbance rather than inherent spatial heterogeneity of species composition.