Species that overlap in physical space are often separated along niche space parameters. We evaluated the niche space of three sympatric high-elevation ground-dwelling squirrels, yellow-bellied marmot (YBM, Marmota flaviventris), Belding’s ground squirrel (BGS, Urocitellus beldingi), and golden-mantled ground squirrel (GMGS, Callospermophilus lateralis). Our survey area encompassed the alpine and subalpine region of the Sierra Nevada in California. We used Ecological Niche Factor Analysis (ENFA) to quantify multivariate niche using an index of Marginality and Specialization, along axes of several climate and habitat variables. This allowed us to identify which of those variables are important predictors of each species presence. We also compared species use of niche space, as well as identified areas of niche space overlap and differentiation between the three considered species. This poster presents the results of the ENFA.
Results/Conclusions
All three species do demonstrate differential use of niche space, through both Marginality and Specialization, when compared to the available niche space. Both of these measures were greatest in the Belding’s ground squirrel, and lowest in the golden-mantled ground squirrel. Slope and topographic roughness (which were highly correlated) were important factors driving Specialization in all species, underscoring the importance of topographic influences on niche space of these species. Summer and winter temperatures were additional important restrictive factors for yellow-bellied marmots. The presence of meadows was the most important factor driving the Marginality in Belding’s ground squirrel and yellow-bellied marmots. Forecasting how individual species may respond spatially to climate change requires knowing niche parameters that are driving current species distributions, and if those parameters are subject to short term change (e.g. temperatures) or not (e.g. slope). The overall magnitude of Marginalization for all three species was driven by a combination of topographic, climatic, and landcover type, not just one type of ecogeographical factor.