Characterization of a Narrow Hybrid Zone Between Two Subspecies of Big Sagebrush (Artemisia tridentata: Asteraceae)

Hybridization between Artemisia tridentata ssp. tridentata and A. t. ssp. vaseyana occurs in a narrow elevational zone along the west face and canyons of the Wasatch Mountains of Utah. Two sites in central Utah (Orem and Salt Creek) were examined. The parental taxa differ in anatomy, morphology, flavonoid and coumarin content, as well as various growth parameters. Hybrids are intermediate for the majority of traits examined, including flavonoid and coumarin composition. Multivariate statistics show that these taxa can be unambiguously identified using simple field measures of morphology. A hybrid index was constructed using principal component analyses on morphological variables.