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Harvard Forest Symposium Abstract 2012
- Title: Does Habitat Restoration Create Butterfly Population Sinks?
- Primary Author: Norah Warchola (Harvard Forest)
- Additional Authors: Greg Breed (Harvard Forest)
- Abstract:
Habitat restoration has the potential to create source-sink dynamics, both because restoration does not restore land to its original quality, and because restoration methods often involve short-term disturbance. Therefore habitat restoration has the potential to reduce population viability, even if animals use restored sites. We are using habitat restoration for endangered butterflies to evaluate the role of source-sink dynamics for population viability, and to determine how these dynamics change through time in response to disturbance. Our studies focus on three threatened and endangered butterflies:
Taylor’s Checkerspot Euphydryas editha taylori is a candidate species for listing as threatened. Found in Washington and Oregon, much of its prairie habitat has been lost to agriculture and development. Remaining prairie habitat is being overgrown due to fire suppression and invasive plants. Taylor’s Checkerspot larvae primarily feed on members of the figwort or snapdragon family (Scrophulariaceae). More recently, some populations have started to use the non-native narrow-leaf plantain Plantago lanceolata. Some habitat restoration plans include large scale planting of P. lanceolata, but little is known about the success of checkerspot larvae feeding on this host plant. We are currently using the ecologically similar, congeneric Baltimore checkerspot Euphydryas phaeton as a surrogate species. Like Taylor’s checkerspot, the Baltimore checkerspot has expanded its host plant specificity to include narrow-leaf plantain.We conducted feeding trials to determine the success of larval Baltimore checkerspots feeding on native and introduced host plants. They show that Baltimore Checkerspot larvae perform better on native white turtlehead than on introduced narrow-leaf plantain. Over the next 4 years, we will explore consequences of non-native host plants for source-sink dynamics of both species in the field.
St Francis’ Satyr Neonympha mitchellii francisci. St. Francis’ satyr is an endangered butterfly known from asingle metapopulation on Fort Bragg in North Carolina. It’s found in wetland habitat dominated by graminoids and sedges. Most subpopulations are found along streams with a mix of active and abandoned beaver complexes. Population persistence often depends on disturbance by beavers and periodic fire that eliminates encroaching woody shrubs and trees.We are currently conducting habitat restoration by implementing inundation and hardwood removal treatments. Over the next 4 years, we will evaluate the habitat quality of restored wetlands in terms of butterfly movement and demography and evaluate whether restoration can create source populations.
Fender’s blue Plebejus icarioides fenderi is an endangered butterfly found in Oregon’s Willamette Valley. Its prairie habitat has been largely lost to development, agriculture and invasive species, with remaining prairie fragments threatened by succession in the absence of historic fire. Prescribed burning is a tool used to slow the encroachment ofwoody plants and to stimulate growth of the butterfly’s larval hostplants, Kinkaid’s lupine Lupinus oreganus and spur lupine Lupinus laxiflorus. We are using experimental burning studies to evaluate the net effects of prescribed burns on butterfly population dynamics. Previous demographic studies indicate that fire kills Fender’s blue larvae, but females lay more eggs in burned habitat, suggesting the potential for switching between source and sink status in burned areas. Preliminary behavioral data suggest that females spent a larger proportion of their active time flying in unburned habitat while they spent a larger proportion of their time ovipositing in burned habitat. Preliminary flight path data indicate that butterflies take shorter flight steps and stop more frequently in burned habitat.
- Research Category: Conservation and Management
