Restoring resources for an endangered butterfly.
Abstract
Recent changes in land use have resulted in dramatic habitat loss for numerous species. More than 99% of the habitat for Fender's blue butterfly Icaricia icarioides fenderi, an endangered butterfly in Oregon, USA, has been lost. Fender's blue butterflies require larval host-plants (Kincaid's lupine Lupinus sulphureus kincaidii) and nectar from native wildflowers. An experiment was conducted at two degraded sites near Eugene, Oregon, to investigate methods for restoration of Fender's blue habitat. The experimental design included four soil treatments (tillage, reverse fertilizer application, solarization and a control) combined with two planting treatments (50% forb seed:50% grass seed and 10% forb seed:90% grass seed) and two weeding treatments (weeding and not weeding). Treatments were replicated in eight experimental blocks (9×28 m) at each site. Seeds from 12 native plant species were field collected and sown in September 1995. Plant establishment was monitored in May 1996, 1997, 1998 and 1999. In 1999, flowers of all nectar species and leaves of Kincaid's lupine were counted. Based on estimates of resource needs from previous work, resources were evaluated as insufficient, sufficient or ample. Solarization combined with 50% forb:50% grass planting promoted sufficient nectar to sustain butterflies at both sites. Control treatments provided insufficient nectar at both sites. None of the treatments produced sufficient larval resources. This experiment demonstrates a method to quantitatively link habitat restoration to the resource needs of focal species. The results emphasize the importance of connecting restoration efforts to the life-history features of focal species. In addition, they highlight the importance of using experiments conducted across a range of sites to test restoration methods before large-scale efforts are implemented.