Habitat distribution models for pygmy rabbits in Idaho

Environmental relationships can differ across the geographic range of
species, especially for widespread generalists.  Because habitat
specialists are more vulnerable to environmental changes, incorrect
assumptions about consistent habitat associations could hinder strategic
conservation efforts.  We used species distribution models (SDMs)
to evaluate intraspecific variation in habitat associations for a habitat
specialist of conservation concern, the pygmy rabbit (Brachylagus
idahoensis), which is endemic to the sagebrush biome of the western
USA.  Our goal was to model habitat associations for pygmy
rabbits across a portion of their range to evaluate regional variation and
contrast predictions with results from a model developed at the rangewide
extent.  We created inductive SDMs using maximum entropy methods
within five ecological regions that encompassed about 20% of the species
rangewide distribution and spanned diverse environmental
gradients.  We included a suite of environmental predictor
variables representing topography, vegetation, climate, and soil
characteristics.  Results of the regional models identified
substantial variation in habitat associations across the five regions,
with each retaining a unique set of environmental predictors. 
Bioclimatic variables were the most influential environmental parameters
in all five regions, but the specific variables differed.  The
models developed at regional extents predicted smaller areas of habitat
(an average of 15% less for suitable habitat and 80% less for primary
habitat) than predictions generated from a model developed at the
rangewide extent.  Because bioclimatic variables were effective
in discriminating areas used by pygmy rabbits, they also provided an
opportunity to assess potential changes in habitat distribution by
incorporating future climate projections.  Distributions modeled
under two mid-century emission scenarios projected substantial reductions
in suitable habitat for pygmy rabbits across most regions and pronounced
variation among regions in the magnitude and direction of the climate
effects.  Collectively, results of this work underscore the need
to incorporate regional variation in habitat associations into planning
for current and future conservation and management strategies.