Identification of Subspecies of Big Sagebrush by Ultraviolet Spectrophotometry

Abstract

The three subspecies of big sagebrush (Artemisia tridentata) are dominant shrubs over much of the Intermountain West. Because the subspecies differ in palatability and habitat requirements, researchers and resource managers have become increasingly concerned with their identification. Subspecies have been identified by leaf morphology, ultraviolet (UV) fluorescence, or chromatography. Fluorescence of leaf extracts under short-wave UV light provides a convenient technique for distinguishing between A.t. vaseyana and the other two subspecies, but this technique will not distinguish between A.t. tridentata and A.t. wyomingensis. Chromatographic techniques can differentiate between all of the subspecies, but the methods are tedious. We describe a technique for distinguishing all three subspecies by UV spectrophotometry. Alcohol leaf extracts of the three subspecies produce relative absorbance graphs that differ markedly from one another between 230 and 280 nm.