Coevolution among plants and herbivores has led to variation in plant defenses and herbivore foraging. Plants must defend against herbivores, whereas herbivores must find ways to overcome plant defenses and meet nutritional needs. Variation in plant quality is important because it can influence selection of plants by herbivores for food. Few studies have investigated the variation occurring within a single plant. Sagebrush offers an excellent system for studying the variation in dietary and chemical quality within a plant. First, variation in nutrition and chemical content exists between subspecies (Kelsey 1982) and between plants of a single subspecies of sagebrush from different geographic locations (Welch 1981). Second, sagebrush has two types of leaves, ephemeral and persistent, and our preliminary data demonstrates that pygmy rabbits prefer ephemeral over persistent leaves leaf types indicating leaf types differ in quality.
Jennifer S. Forbey