Symbioses: Plant, Animal, and Microbe Interactions
Auger, Janene , Meyer, Susan E. .
Blackbrush (Coleogyne ramosissima) - Ord.
BLACKBRUSH (Coleogyne ramosissima) is the dominant shrub species on shallow soils over much of the Colorado Plateau, often forming dense, monospecific stands. It is a mast-seeding species with large seeds dispersed by scatter-hoarding heteromyid rodents. We followed populations of Ord's kangaroo rat in relation to blackbrush seed production events from 1997 through 2001. In a blackbrush-dominated community, blackbrush seeds provided 70% of the total seed biomass available to kangaroo rats in a mast year, while in the following year this value fell to near zero. Kangaroo rat population size tracked yearly variation in blackbrush seed production. In a mixed shrub-grassland community on sand hummocks with a more even production of seeds across years, kangaroo rat population size was more stable. Kangaroo rat home range size in blackbrush-dominated habitat varied as a function of seed resource availability in a resource-limited non-mast year but not in a mast year. In cafeteria trials, blackbrush seeds were not highly preferred but were readily taken and consumed. Kangaroo rats in this ecosystem appear to use blackbrush seeds opportunistically and to increase their numbers and the size of the areas they occupy dramatically when this food resource becomes abundant in a mast year. Blackbrush, on the other hand, relies exclusively on kangaroo rats and other heteromyids to carry its seeds away from the competitive environment of the maternal plant and to plant them at a depth where they are safe from other predators and in an optimum microenvironment for successful establishment. The evolution of mast-seeding in blackbrush appears to be at least in part a response to selection for heteromyid dispersal. By satiating their dispersers, who are also the primary predators on blackbrush seeds, blackbrush populations have the potential to successfully recruit new seedlings following mast events.[c.e.:srb]
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1 - Department of Plant and Animal Sciences, Brigham Young University, Provo, Utah, 84602, USA
2 - USDA Forest Service, Rocky Mountain Research Station, Shrub Sciences Laboratory, 735 N 500 E, Provo, Utah, 84606, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 31st, 2006
Time: 8:30 AM