GENETIC DIVERSITY AND GENE FLOW IN THE ENDANGERED DWARF BEAR POPPY, ARCTOMECON HUMILIS (PAPAVERACEAE)

Arctomecon humilis is a critically endangered species endemic to the M oenkopi shale of Washington County, Utah. Recovery plans for the speci es would: be improved by an understanding of genetic diversity and gen e flow among its remaining populations. Ten variable isozyme loci were used to calculate genetic diversity statistics for study populations. Westerly populations possessed higher levels of genetic variability t han other populations at the same isozyme loci. Three of the populatio ns exhibited significant deviations from Hardy-Weinberg expectations. No correlation existed between genetic distance and geographic distanc e. Most of the genetic diversity was distributed among populations wit h little gene flow between populations, suggesting that observed genet ic differences may arise from genetic drift. For the westerly populati ons, similar genotypes were observed in the seedling and old age class es, while intermediate age classes typically possessed an alternate se t of genotypes at Pgi-2. Mean heterozygosity increased with age class across populations. Westerly populations of A. humilis shared more all eles with the nearest geographic population of A. californica than oth er populations. Since the westerly populations contained more genetic variability and more alleles in common with a near relative, they may be relictual. Other populations may contain less genetic diversity due to founder effects and/or genetic drift.