Da. Kelt, Assemblage structure and quantitative habitat relations of small mammals along an ecological gradient in the Colorado Desert of southern California, ECOGRAPHY, 22(6), 1999, pp. 659-673
Ecological gradients have intrigued ecologists for many years. In southern
California the Deep Canyon Transect spans a range of habitats and elevation
s from Lower Sonoran Desert sand dunes and creosote scrub to Upper Transiti
on coniferous forest, where relict species typical of the Sierra Nevada are
found. I sampled a 1050 m elevational range in this transect to evaluate t
he ecological distributions of small mammals and to better characterize com
munity structure. Results complement and substantially extend a previous st
udy of this fauna, and provide insights into the habitat associations of sp
ecies in this complex fauna. Assemblage structure changed greatly between s
ummer and winter, largely due to reduced presence of pocket mice Chaetodipu
s in winter. Additionally. the distribution of abundance and species richne
ss was different than reported earlier, suggesting that patterns across thi
s gradient may be temporally variable, and strongly influenced by local dyn
amics. Most taxa exhibited significantly nonrandom use of a large number of
habitat variables but this was nor a simple consequence of the elevational
gradient. A mid-elevation bulge in species richness was indicated, bur lik
ely is nor a consequence of mass effects since a number of animals captured
in intermediate regions were reproductively active.