Abstract
BackgroundDifferent processes determine species’ geographic ranges, including species’ responses to changing climate, habitat, or both simultaneously. Here we ask which combination of factors best predicts shifts in the upper and lower elevation range limits and overall range of small mammal species in Yosemite National Park, California, USA across the last 100 years.MethodsWe used species distribution models (SDMs) to predict elevation range dynamics of small mammals between 1910 and 1930 and 2003 and 2010, based on combinations of habitat and climate variables, and compared the predicted SDM distribution with the “observed” range from occupancy modelling (OM).ResultsSDM model convergence was successful for eight species. Predictions of elevation range shifts from the SDMs agreed with OM for four of these species; while the other four could be partially predicted. SDMs predicted shifts in lower limits (six correct) better than upper limits (five correct). The five correctly predicted upper limit shifts were best predicted with climate; whereas five out of the six lower elevation shifts included habitat. SDMs were best at predicting range contraction at higher elevations.ConclusionsClimate generally had a stronger effect on range dynamics than habitat, especially at higher elevations. However, at mid-elevations SDMs showed an increasing importance of habitat on range shifts at these elevations, in the cases range shifts were reliably predicted. Predicting elevation range shifts on the basis of climate or habitat alone is insufficient, as habitat and climate play varying roles at different elevations, associated with different processes underlying range shifts. Failure to predict observed range shifts may arise from biotic interactions, behaviour flexibility, or evolutionary adaptation, aspects which are only beginning to be incorporated into distribution modelling frameworks.
Highlights
Different processes determine species’ geographic ranges, including species’ responses to changing climate, habitat, or both simultaneously
We examine whether the recorded elevation range shifts of eight small mammals inhabiting a variety of elevation ranges across Yosemite National Park, California, USA [5], are matched by predictions from species distribution models (SDMs)
The Brush mouse (P. boylii) did not display a change in its overall range which was correctly predicted by the climate-only SDM (Table 2)
Summary
Different processes determine species’ geographic ranges, including species’ responses to changing climate, habitat, or both simultaneously. Changes in temperature and precipitation affect plant distribution [18], physiology and phenology [19, 20], influencing plant productivity and the production of food resources that fauna may depend on. These vegetation-mediated climate effects may show a lag, a slow down or neutralization of the animals’ responses to direct climate effects as animals may stay present as long as the habitat provided by vegetation does [1]. Changes in moisture can affect metabolic costs arising from getting wet (i.e., from rainfall) [29] and from difficulties in thermoregulation through transpiration when relative humidity is high [22, 26]
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