Forest fragmentation and its effects on Lepidoptera species and their associated larval parasitoids

Background/Question/Methods

Habitat fragmentation is a serious threat to biological diversity on a worldwide scale. It is critical that we understand factors that lead to extinction of populations of organisms due to habitat fragmentation so that we can work towards viable solutions to this extensive, devastating ecological problem. In many instances, damaged ecosystems also become more vulnerable to invasions by exotic species, which often results in additional stress on populations of native species that are already struggling to survive. Thus, it is imperative that effective solutions to habitat fragmentation be found.

Moths and butterflies are nearly ideal organisms for monitoring perturbations to both tropical and temperate ecosystems, because these insects are widely distributed, relatively easy to sample, and sensitive to destruction of their plant resources. This research project is an investigation of the effects of habitat fragmentation on forest Lepidoptera (moths and butterflies) and their associated larval parasitoids (in this particular study, parasitic wasps and flies). The hypotheses were: 1) Larger forests have a greater Lepidoptera species diversity than smaller forests; 2) More isolated forests have a lower diversity than forests that have other forests near to them; and 3) Larval parasitoid assemblages are less diverse in smaller, more isolated forests. Lepidoptera larvae (caterpillars) were collected during 2006 and 2007 in small and large woodland habitats located within a highly fragmented landscape of northwestern Ohio. The collected larvae were reared under suitable laboratory conditions in order to determine assemblages of parasitoids associated with the moths and butterflies occurring within the different forest habitat patches.

Results/Conclusions
Results indicate that forest fragmentation has an impact on Lepidoptera communities and their associated larval parasitoid assemblages. Larger forests had a greater diversity of Lepidoptera as well as larval parasitoids. Because this research includes an examination of the parasitoids of the larvae of Lepidoptera occurring in fragmented forest environments, the influences of habitat fragmentation on communities of herbivorous insects and their predators will be elucidated. Relatively few research investigations to date have studied habitat fragmentation in a tritrophic context, i.e., examining the plants of the forests, the moth and butterfly caterpillars, and the parasitoids using the caterpillars as hosts simultaneously in fragmented landscapes.