SREL Reprint #2651

Clonal diversity in two rare perennial plants: Sagittaria isoetiformis and Sagittaria teres (Alismataceae)

Adrienne L. Edwards1 and Rebecca R. Sharitz2

1Illinois Natural History Survey, 607 East Peabody Drive, Champaign, Illinois 61820, U.S.A.
2Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802, U.S.A.

Abstract: Most perennial herbs can produce clones (genetically identical ramets), and the frequency of asexual propagation relative to sexual reproduction can affect genetic and genotypic diversity. The power to detect clones also depends on marker diversity. Using horizontal starch-gel electrophoresis, we surveyed two rare perennials found in isolated wetlands: Sagittaria isoetiformis, restricted to the inner coastal plain of southeastern North America, and Sagittari teres, endemic to glacial ponds in northeastern North America. Fifteen polymorphic loci were resolved on 527 individuals across 11 populations (ca. 48 ramets/population) for S. isoetiformis, and 12 polyinorphic loci were resolved on 367 individuals across seven populations (ca. 52 ramets/population) for S. teres. Although genets commonly produce clones in these species, we found no significant influence of genotype duplication on genetic structure. Genotypic structure and our power to detect clones did differ among species. The proportion of distinguishable genotypes per population was higher in S. isoetiformis (G/N = 0.92 ± 0.12) than in S. teres (G/N = 0.54 ± 0.21). When standardized by the number of polymorphic markers in each population, genotypic diversity was high in both species (D = 0.99 in S. isoetiformis and D = 0.94 in S. teres), but genotypes were less evenly distributed across S. isoetiformis populations (E = 0.75), ranging from 0.60 to 1.00, than across S. teres populations (E = 0.84), ranging from 0.80 to 0.92. Overall, we had greater power to detect unique genotypes in S. isoetiformis than in S. teres, demonstrating the importance of reporting some measure of statistical power to distinguish genetic individuals. The combined genetic and genotypic evidence indicates that sexual recruitment from persistent seed banks helps to maintain genetic and genotypic diversity in these species.

Keywords: allozyines, clonal growth, genotypic diversity, rare plants, Sagittari isoetiformis, Sagittaria teres, wetland perennials

SREL Reprint #2651

Edwards, A. L. and R. R. Sharitz. 2003. Clonal diversity in two rare perennial plants: Sagittaria isoetiformis and Sagittaria teres (Alismataceae). International Journal of Plant Sciences 164:181-188.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).