AN ANALYSIS OF GENETIC-VARIATION IN ASTRAGALUS-CREMNOPHYLAX VAR CREMNOPHYLAX A CRITICALLY ENDANGERED PLANT, USING AFLP MARKERS

A recently developed molecular technique (amplified fragment length po lymorphisms, AFLP) was used for characterizing genetic heterogeneity w ithin and among populations of a critically endangered species of plan t, Astragalus cremnophylax var. cremnophylax. Using AFLP, up to 50 pol ymorphic genetic markers per AFLP-PCR amplification were generated, an d a total of 220 variable markers overall. This information was used f irst to assess genetic diversity within each of the three known popula tions of Astragalus cremnophylax var. cremnophylax from Grand Canyon N ational Park in Arizona, USA: North Rim (NR; n = 970), South Rim Site 1 (SR1; n = 500), and South Rim Site 2 (SR2; n = 2). Diversity in the form of average heterozygosity (H) and the proportion of polymorphic g enes [P] was greatest in the NR population ([H]= 0.13 and [P] = 0.38) and least in the SR2 population ([H] = 0.02 and [P] = 0.04). Diversity was also quite low for the SR1 population ([H] = 0.04 and [P] = 0.10) . In addition, substantial genetic differentiation among populations w as indicated by both phenetic (AMOVA) and genetic analyses (overall co rrected F-ST = 0.41). This finding was corroborated by the results of several multivariate analyses which utilized the genetic data, includi ng a UPGMA cluster analysis and a principal coordinate analysis which revealed the existence of discrete groups corresponding to the populat ions. Population structure was further revealed within the NR populati on which was known to consist of four spatially separated groups of pl ants. Several recommendations for the future management of the species are discussed.