AUTHORS: Federico Riva*, University of Alberta and Land Reclamation International Graduate School; John H. Acorn, University of Alberta; Scott E. Nielsen, University of Alberta and Land Reclamation International Graduate School
ABSTRACT: Understanding the interplay between ecological processes and spatial patterns across multiple scales is an important focus of landscape ecology. Because this relationship determines species’ occurrence, it is also fundamental in conservation planning, especially when the aim is to protect a rare species. One native species of conservation interest in North America is the cranberry blue butterfly (Plebejus optilete). In Alberta, Canada, the cranberry blue is considered imperiled with few occurrences known (< 15), generally in treed peatlands. There is concern that this species will be negatively affected by anthropogenic disturbances associated with seismic assessments of underground oil sands reserves. These disturbances are narrow (< 10 m), but dense (up to 40 km/km2), early seral corridors cleared across thousands of km2 of boreal forests, including where cranberry blues are found. Here, we investigated how variation in patterns in natural and anthropogenic forest characteristics affect the occurrence of cranberry blue butterflies. Forests in the region naturally transition from wetland to upland environments, and are characterized by periodic wildfires. To examine responses of cranberry blues to wildfires and anthropogenic sources of disturbance, we sampled butterflies along 250-m transects at five point-counts across 40 sites, and modeled the species occurrence based on fire severity, forest structure, forest fragmentation, and soil wetness, each measured directly at the site and at the landscape with a GIS.In total, we discovered 14 new populations across a 2,500-km2 region of northeast Alberta. Cranberry blues preferred open treed peatlands, and were sensitive to local variation in habitat. While we found no evidence of negative effects from the anthropogenic forest corridors, recent wildfires decreased species occurrence. Although local characteristics are the primary determinant of species occurrence, amount of surrounding treed peatland conditioned the local presence of cranberry blues, confirming that the landscape can fulfill important roles in moderating ecological processes.
