ALLOZYME VARIATION,GENECOLOGY, AND PHYTOGEOGRAPHY OF ANTENNARIA ARCUATA (ASTERACEAE), A RARE SPECIES FROM THE GREAT BASIN AND RED DESERT WITH SMALL DISJUNCT POPULATIONS

Antennaria arcuata (Asteraceae: Inuleae) is a rare sexual diploid species that occurs in three disjunct regions of Idaho, Nevada, and Wyoming. Isozyme diversity in six populations of the species from the three regions utilized 26 putative loci to provide clues to its population genetic structure. Results show that, in general, the amount of genetic diversity in A. arcuata is very low in comparison to other sexual species of Antennaria. The values of several genetic statistics such as mean number of alleles per locus, proportion of loci polymorphic, and observed heterozygosity, are significantly lower than populations of any of 17 other sexual species of Antennaria that have been studied previously. It is likely that the unusual disjunct and restricted distribution of A. arcuata is partially the result of its unusual ecology, as it occurs in moist basins having high concentrations of salts that are frequently disturbed by large grazing animals. Canonical correspondence analysis shows strong relationships between several edaphic, environmental, and geographic features and the genetic variation in the populations. The migration of A. arcuata to other regions since the end of the Wisconsinan might have been inhibited by the fact that suitable habitats occur as small isolated islands in a sea of inhospitable terrain, the dry sagebrush steppe.