Population Genetic Structure of Arctomecon californica Torrey & Frémont (Papaveraceae) in Fragmented and Unfragmented Habitats

Arctomecon californica (the Las Vegas bearpoppy) is endemic to gypsum outcrops of the northern Mojave Desert. Native habitat of this plant in the Las Vegas Valley has been severely fragmented, while relatively undisturb ed, unfragmented habitat still exists in the Lake Mead National Recreation Area. Allozyme data from seven loci for 16 populations indicate high levels of genetic variability. Neis genetic identity and GST values suggest that populations in fragmented habitat are more differentiated with increasing geographic distance. Populations in unfragmented habitat show no relationship between geographic distance and genetic identity. Three indices of genetic variation were significantly lower for populations in fragmented habitat. However, there was little evidence of increased inbreeding, as indicated by fixation indices, for any population. Habitat fragmentation is discussed as a possible contributing factor to reduced levels of genetic variation in populations in the Las Vegas Valley