Habitat fragmentation associated with deforestation is likely to have major effects on the community structure of forest dependent insects. Increased invasion of fragmented habitat by non-native plant species may exacerbate the direct effects of fragmentation. We surveyed caterpillars in forest fragments in southwestern Ohio in order to understand the effects of forest fragmentation and invasive species (honeysuckle: Lonicera maackii) on Lepidoptera species richness and abundance. Caterpillars were surveyed in ten forest fragments along 100m transects that began at the forest edge. Eight transects were conducted in each fragment and caterpillars were collected from focal tree species along each transect. Honeysuckle density was also measured along these eight transects in order to quantify the effects of honeysuckle on Lepidoptera diversity. To experimentally determine the effects of honeysuckle on Lepidoptera herbivory, twelve sugar maple saplings (Acer saccharum) were planted in six forest fragments. Six saplings were planted in areas of high honeysuckle density and six saplings were planted in areas of low honeysuckle density. All leaves on the saplings were examined at the end of September for insect herbivory.
Results/Conclusions
Within the ten forest fragments surveyed we collected 929 caterpillars belonging to 14 families on 24 tree species. We found that as fragment size increased, the number of individual caterpillars collected also increased. Also, the number of caterpillar species collected increased with increasing fragment size. The species richness of caterpillars was negatively correlated with honeysuckle density. These results suggest that honeysuckle does not negatively affect the abundance of caterpillars in forest fragments, but rather the diversity. We found no relationship between forest fragment size and honeysuckle density. In the experimental test of honeysuckle density on insect herbivory, we found a significant positive affect on herbivory in the areas of high honeysuckle density in two of our sites (p=0.002). These findings suggest that in areas of high honeysuckle density, high quality plant material may be at a deficit and therefore the plant species within these honeysuckle areas may act as sinks for herbivory. These results show that habitat fragmentation, compounded with exotic species invasion, can decrease Lepidoptera diversity and therefore lead to an overall decrease in biodiversity in southwestern Ohio.
