On early-Holocene moisture and small- mammal histories in the Bonneville basin, Western United States

摘要

Comparisons of Bonneville basin small-mammal skeletal assemblages from low-elevation caves with a collection from an upper piedmont rock shelter support Oviatt et al.'s hypothesis that early-Holocene moisture may have been the result of groundwater discharge rather than precipitation and runoff. After cool and moist late-Pleistocene environs were replaced by warmer and drier Holocene climates, low-elevation small-mammal communities increased in taxonomic richness and evenness and continued to support large numbers of rodent and leporid species well-adapted to mesic contexts. At the same time, the more upland small-mammal community along the Bonneville shoreline on the basin's margin experienced declines in richness and evenness and the extirpation of a number of mesic-adapted mammals. Overall differences in the composition of these early-Holocene assemblages suggest the basin bottom sustained moist and energetically auspicious habitats considerably longer than regional adjacent uplands, and it is possible that this low-elevation moisture was the result of Pleistocene Lake Bonneville groundwater discharge.