PARENT SESSION
Oral Session 4: Biodiversity I: Communities and Function.
Presiding: C Holzapfel and D Ellsworth
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 110.
Elevational gradients in small mammal diversity: Mid-elevation peaks and effects of climate, latitude, and area.
McCain, Christy*,1, 1 National Center for Ecological Analysis and Synthesis, Santa Barbara, CA, USA
ABSTRACT- A global analysis of elevational diversity trends for non-volant small mammals revealed a ubiquitous pattern of mid-elevational peaks in species richness. Fifty-one elevational data sets were used to test the predictions of a null model, the mid-domain effect, and climatic hypotheses. Very few data sets fit entirely within the 95% prediction curves of the null model, as the average predictive power of the null model was low (r2 = 38%). Gamma data fit predictions of the null model better than alpha data (70% and 33% significant r2 values, respectively). Diversity peaks occurred at higher elevations on taller mountains (Massenerhebung effect), which is consistent with climatic factors working in concert to produce elevationally correlated habitat bands. Such a positive, linear relationship was documented for the combined data sets (r2 = 44%, P = 0.0000) and for tropical, island, and continental sets, but was particularly pronounced in alpha data sets (r2 = 70%, P = 0.0001). Gamma diversity studies, which are highly influenced by increased area at lower elevations; exhibited a negative, linear trend of diversity peaks shifting to lower elevations on taller mountain ranges (r2 = 28%, P = 0.01). Gamma diversity patterns also demonstrated higher altitudinal peaks in species diversity as latitude increased (r2 = 26%, P = 0.02). These results are evidence for the importance of a suite of interacting climatic factors on elevational diversity patterns that is apparent even with the noise from different sampling techniques, localities, and historical pressures.
Key words: elevational gradient, small mammals, alpha and gamma diversity, mid-domain effect