Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/7/2004
Publication Date: 7/9/2004
Citation: Longland, W.S. 2004. Granivory by desert rodents and local extinction of an exotic invasive weed [abstract]. Ecological Society of America, August 1-6, 2004. 89:110.
Technical Abstract: At a sandy desert site in western Nevada the exotic annual cheatgrass (Bromus tectorum) initially invaded in 1994 and maintained high densities through 2000, during which time its seeds were an important food resource for the local rodent community. However, the plant has since been absent. Emergence of clumped cheatgrass seedlings from rodent scatterhoard caches, plummeted from 121 to 2 caches/1-km transect between 2000 and 2001, suggesting that rodents were no longer able to use cheatgrass seeds as a food resource. Despite their strong preference for Indian ricegrass seeds, a field experiment showed that significantly more buried cheatgrass caches (46-69%) were removed by rodents over 10 days relative to paired caches of Indian ricegrass seeds (13-44%), indicating that cheatgrass seeds are more detectable by olfaction. Similar results were obtained in laboratory cache removal experiments with captive rodents of 2 species (Dipodomys merriami and Chaetodipus formosus). The former rodent species is abundant on sands at the field site, while the latter occurs exclusively on adjacent clay soils with a basalt covering. The differing seed use patterns of rodent species typifying clay versus sandy soils and safesites offered by basalt rocks facilitate the persistence of cheatgrass in low densities in the former habitat while it has gone locally extinct on the sands.