GENETIC DIVERSITY IN A CLONAL NARROW ENDEMIC, ERYTHRONIUM PROPULLANS, AND IN ITS WIDESPREAD PROGENITOR, ERYTHRONIUM ALBIDUM

Abstract

Erythronium propullans is a narrow endemic restricted to two counties in southeastern Minnesota. It coexists at all sites with the widespread common white trout lily, E. albidum. Erythronium albidum has both sexual and asexual reproduction; it has been suggested that E. propullans reproduces strictly by vegetative means. Electrophoretic analysis of 15 enzyme systems encoded by a minimum of 37 genetic loci revealed considerable genetic variation within and among E. propullans populations. However, all measures of variability calculated from allozyme data demonstrate that E. propullans maintains lower levels of genetic variation than E. albidum. There is also evidence for limited gene flow among E. propullans populations, whereas all E. albidum populations are genetically similar. Clonal diversity is also lower in E. propullans. Only 21 clones were found in 100 individuals sampled whereas virtually every one of the 70 individuals of E. albidum sampled had a unique multilocus genotype. The clones of E. propullans cluster into 3 genetically dissimilar groups; variation within each cluster indicates that some sexual recombination does occur. We discuss the effects of clonality and endemism on genetic variation, reasons why the clonal habit might preserve genetic variation, and suggest that the lower variability in E. propullans is due primarily to the genetic bottleneck it experienced at the time of its origin. Isozyme data suggest that E. propullans is a derivative of E. albidum. Based on the degree of genetic similarity and information on the glacial history of the region, we suggest that E. propullans is a local derivative of E. albidum, having arisen no more than 9,000 years ago.