Ecological determinants of species diversity and community composition of forest moths (Lepidoptera) at local and regional scales

Historically, research on the Lepidoptera in temperate forest systems focused on characterizing local faunas and monitoring the population dynamics of economically destructive species. The Lepidoptera, however, are among the more functionally important insect groups inhabiting temperate forests, and many lepidopteran communities currently occur in forests subject to large disturbances such as timber harvest or habitat fragmentation. Our current understanding of the community ecology of Lepidoptera in temperate forests is not sufficiently developed to determine how such disturbances affect moth community structure. Thus, the purpose of this dissertation was to address two major questions. First, how is moth species diversity and composition determined at local and regional scales? Second, how do disturbances such as logging and forest fragmentation affect moth biodiversity and community composition?; Using 12-W blacklight traps, I sampled a total of 81,170 moths, comprising 917 species (≈7 species previously unknown to science) between 1999 and 2001 from state parks, state forests, nature preserves and private woodlots in Ohio and Indiana. Moth communities displayed significant seasonal variation, with less than 40% similarity observed between June and August in each year of study. Additionally, moth community composition was affected by floristic variation among stands at local and ecoregional scales. At local scales, stand age and tree species diversity influenced which moth species were found within a forest stand. At ecoregional scales, differences in the development of the herbaceous understory, the importance of oaks, and the diversity of shrubs affected lepidopteran community composition. Logging significantly decreased lepidopteran richness in clear-cut forests but not in selectively logged stands. Finally, forest stand area and habitat heterogeneity were the best predictors of local moth diversity in fragmented forest systems.; In conclusion, my dissertation indicates that moth community structure is significantly influenced by fine- and broad-scale variation in forest vegetation as well as the size of the stand. Because moth communities respond strongly to changes in forest vegetation, managing forest stands for habitat quality may be as important as conserving large patches of forest for the long-term maintenance of forest moth biodiversity.