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Abstract
Basin big sagebrush (Artemisia tridentata ssp. tridentata) and mountain big sagebrush (A. t. ssp. vaseyana) hybridize in a narrow zone near Salt Creek, Utah. Reciprocal transplant experiments in this hybrid zone demonstrate that hybrids are more fit than either parental subspecies, but only in the hybrid zone. Do hybrids experience greater, or lesser, use by herbivorous insects, especially in the hybrid zone? And do certain species of herbivorous insects prefer one or the other parental subspecies of big sagebrush? We studied plant-insect interactions in three reciprocal transplant gardens that span the hybrid zone at Salt Creek. Gardens were in the basin and mountain big sagebrush zones and also in the hybrid zone. Transplanted seedlings came from two parental and three hybrid source populations. Densities of herbivorous insects varied among the gardens and source populations, but the interaction between garden and source population was statistically insignificant. Most of the variation in herbivore density was among gardens, rather than among source populations. Only grasshoppers and lepidopteran leaf miners showed significant preferences among the source populations; grasshoppers preferred mountain big sagebrush and leaf miners preferred near-basin hybrids. Coccids, Clastoptera, Trirhabda, coleophorid larvae, and lepidopteran leaf miners showed significant differences in density among the gardens. Finally, the hybrids were not a sink for herbivorous insects, nor did they have lower herbivore loads.
Parent Publication
Citation
Graham, John H.; McArthur, E. Durant; Freeman, D. Carl. 2001. Narrow hybrid zone between two subspecies of big sagebrush (Artemisia tridentata: Asteraceae): XI. Plant-insect interactions in reciprocal transplant gardens. In: McArthur, E. Durant; Fairbanks, Daniel J., comps. Shrubland ecosystem genetics and biodiversity: proceedings; 2000 June 13-15; Provo, UT. Proc. RMRS-P-21. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 118-126.
