Patterns of ectomycorrhizal-fungi consumption by small mammals in remnant old-growth forests of the Sierra Nevada

We investigated fungal consumption and resulting patterns of potential spor e dispersal by 6 small mammals in old-growth habitat in the Sierra Nevada o f the United States, a region in which this ecological interrelationship is poorly understood. Small mammals consumed a wide array of food items, alth ough only feces of northern flying squirrels (Glaucomys sabrinus), golden-m antled ground squirrels (Spermophilus lateralis), and Douglas squirrels (Ta miasciurus douglassi) frequently contained spores of hypogeous fungi, where as those of lodgepole chipmunks (Tamias speciosus), long-eared chipmunks (T . quadrimaculatus), and deer mice (Peromyscus maniculatus) did so rarely. F eces from the 3 squirrel species also contained a greater number of hypogeo us fungal genera per sample than did samples from the latter 3 species. Fly ing squirrels potentially dispersed the greatest variety of ectomycorrhizal fungi (16 genera): 8 in spring and 15 in autumn. Frequency of occurrence o f 9 genera in the feces of flying squirrels differed between spring and aut umn. Interspecific differences in patterns of fungal consumption, coupled w ith differences among these small mammals in habitat use, mobility, and dig estive physiology, suggest that these small mammals may disperse fungi in e cologically nonredundant ways and that the integrity of entire small-mammal communities may be important to the maintenance of ectomycorrhizal diversi ty in coniferous forests.