Collaborative Research: Effects of forest fragmentation on Lepidopteran herbivores of contrasting diet breadth

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The fragmentation of habitats in to smaller and more isolated pieces can leave animals in areas that have insufficient food resources within reach. This problem is particularly acute for those species that are dietary specialists. These specialists may then be lost from the habitats, and their loss can have cascading effects on other species that may further alter the composition of ecological communities. This project will test alternative hypotheses that have been proposed to explain declines in specialist herbivores from fragmented forests. This research is important in understanding how changes in land use or other disturbances that fragment habitats will affect biodiversity and the integrity of ecosystems. The project will focus on butterfly larvae of species with different diet requirements as model study organisms. Their dependence on particular plant species and their role as prey for birds will be studied in 40 forest sites in Connecticut where the basic ecological interactions are well known. In addition to analysis of response to past forest fragmentation, experiments protecting caterpillars from predation will help quantify the importance of food resources. The study will improve understanding of natural food webs subject to human impacts and can guide future forest management. This project will also provide research training for students in forest ecology that will strengthen the scientific workforce.Forest fragmentation is likely to substantially modify interactions among species and a recurrent pattern is the loss of dietary specialists from food webs in small forest fragments. Focusing on a complex, tri-trophic ecological network of larval Lepidoptera, their hostplants and avian predators, the project will establish how bottom-up and top-down mechanisms alter the absolute and relative abundance of specialist herbivores in forest fragments. The project will combine extensive extant data on plant-Lepidoptera associations and regional forest fragmentation, new data on plants and caterpillars at 40 sites, field experiments, and lab analyses on caterpillar diet breadth and growth response to quantify effects of host plant availability and predation on the diet specificity of lepidopteran larvae in temperate deciduous forests. This detailed, multi-trophic approach will enhance mechanistic understanding of changes in trophic networks due to fragmentation. Four broader impacts will result from this work: 1) training future scientists, 2) recruiting underrepresented groups, 3) public outreach in science and 4) improving scientific infrastructure.