GENETIC DIVERSITY AND POPULATION-STRUCTURE OF YUCCA-FILAMENTOSA (AGAVACEAE)

Using 19 allozyme loci we studied genetic diversity in 18 populations of Yucca filamentosa (Agavaceae) from the southeastern United States. Of the 19 loci surveyed, 17 (89.5%) were polymorphic in at least one a f the populations sampled. There was considerable variation among popu lations in the percentage of polymorphic loci (range = 31.6-84.2%, mea n = 67.6%). Similar heterogeneity among populations was observed for m ean number of alleles per polymorphic locus (range = 2.0-3.0; mean = 2 .48) and mean expected heterozygosity (range = 0.113-0.288: mean = 0.2 13). On average, 83% of the total genetic diversity was found within p opulations. Duplications of three allozyme loci were detected in sever al populations. The life-history characteristics of Y. filamentosa (a long-lived, semiwoody. predominantly outcrossing monocot with a large geographical range) may contribute to the maintenance of such high lev els of genetic diversity. These results contradict expectations of the genetic structure of Y. filamentosa based on observations of the disp ersal and pollination behavior oi its sole pollinator, Tegeticula yucc asella, the yucca moth.