Idaho populations of Eriogonum shockleyi are taxonomically divided into two varieties. These are E. shockleyi var. packardae, which is endemic to Idaho, and the typical variety is widespread in the western United States. Recent morphological investigations of E. shockleyi in Idaho have identified potentially reliable morphological characters for field identification of the subspecific taxa. This paper investigates the genetic basis for the separation of the two varieties of E. shockleyi using ISSR markers. Although there were some morphological differences found between the populations that correlated with the two varieties, there were no molecular markers identified in this study to distinguish between them. Morphological measurements obtained in the field indicate that although a population may have an overall average morphology that defines the variety, some individuals in nearly all populations have putative diagnostic characters that define the other variety. The morphological characters used to distinguish the two varieties are most likely the result of environmental variability and could result from differences in precipitation and soil water retention. Alternatively, high levels of outcrossing through pollen flow could be obscuring selection for morphological characters at particular sites.

Key words: Eriogonum shockleyi, ISSR, Polygonaceae, varieties