We used electrophoretic analysis of isozymes to investigate genetic structure of the Mojave Desert endemic, Yucca brevifolia. To test the hypothesis that, because of geographic isolation, most variation in allele frequencies would be between populations we sampled three subpopulations in each of five distinct populations: Arizona, Joshua Tree, Mojave, Western Mojave, and Utah. Two of nine proteins had isozymes that resolved adequately. One of these, Superoxide dismutase (SOD) was monomorphic. For the other, glucose-6-phosphate isomerase (GPI), five alleles were identified, and the three most common alleles were present in all populations sampled. For GPI, allele frequencies differed significantly between all five populations, as well as between subpopulations in both the Joshua Tree and Arizona populations.

We also tested the hypothesis that there would be strong localized genetic structure due to the high proportion of recruitment attributed to vegetative reproduction. Based on GPI data from an intensively sampled 1 ha plot, genotypes were randomly distributed, and thus sexual reproduction through outcrossing may be the principal mode of recruitment in Y. brevifolia at this site.

This study describes genetic structure within populations of Y. brevifolia based on protein variation at a single locus. Future research, using additional markers (nuclear, cytoplasmic, or both) is necessary to understand the dynamics of gene flow, genetic variation, and recruitment within the species Y. brevifolia