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New Records of Marginal Locations for American Pika (Ochotona princeps) in the Western Great Basin

Millar, Constance I., Westfall, Robert D., Delany, Diane L.
Western North American naturalist 2013 v.73 no.4 pp. 457-476
Laridae, Ochotona, atmospheric precipitation, basins, bedrock, biogeography, habitats, hills, lava, mining, shrublands, surveys, viability, California, Nevada
We describe 46 new site records documenting occupancy by American pika (lOchotona princeps) at 21 locations from 8 mountain regions in the western Great Basin, California, and Nevada. These locations comprise a sub- set of sites selected from regional surveys to represent marginal, isolated, or otherwise atypical pika locations, and to provide information for assessing environmental tolerance limits. Several locations are known from historic observations (Madeline Plain, Bodie Mtns., Wassuk Mtns., Mono Craters) and are included here to update current status. Site eleva- tions range from 1848 m to 3392 m; relative to the broad range of pika sites in the region, the new locations have cli- mates that are 2—4 °C warmer and receive approximately half the annual precipitation. Sites are located in lava flows and domes, inselbergs (isolated, rocky exposures on a small hill), eroding bedrock, rock-glacier till, talus slopes, and anthro- pogenic roadbed armaments and mining ore dumps. Several sites are situated in uncommon vegetation contexts, for example, montane desert scrub communities or locations where vegetation adjacent to taluses is sparse or lacking. Prox- imity to surrounding pika habitats (as a measure of marginality) was evaluated based on relative talus distribution pat- terns for 0.5-km, 2.5-km, and 5.0-km circular areas nested around each site. Seven idealized, schematic spatial patterns were used to assess potential connectivity among sites, ranging from “island” (no other talus within the respective areas) to “even” (many talus patches regularly distributed). Applying this approach to the 21 sites demonstrated a simple method for qualitatively assessing pika habitat relative to dispersal potential and metapopulation viability and also revealed complexities of biogeographic patterns related to marginality.