The importance of understanding clonal structure for species listing and recovery: case studies from the rare oconee bells (Shortia brevistyla and Shortia galacifolia; Diapensiaceae) and the federally endangered bunched arrowhead (Sagittaria fasciculata; Alismataceae)

Understanding genetic structure in rare plant populations is essential to making informed decisions for recovery actions, particularly in species capable of clonal reproduction. Here, we present three case studies using microsatellites to assess clonal structure in rare plants: Northern Oconee bells (S. brevistyla (P.A. Davies) Gaddy) and Southern Oconee bells (Shortia galacifolia Torr & Gray) (Diapensiaceae); and bunched arrowhead (Sagittaria fasciculata E.O. Beal (Alismataceae)). We used six loci to genotype Shortia brevistyla (n = 62 ramets; three sites) and S. galacifolia (n = 111 ramets; seven sites) and five loci in Sagittaria fasciculata (n = 162 ramets; eight sites). Ramets were systematically mapped and sampled to allow for clonal assignment in a spatial context. All ramets for S. brevistyla were genetically identical across all loci, while S. galacifolia exhibited variation consistent with a mixed reproductive strategy. Sagittaria fasciculata also exhibited a mixed reproductive strategy with emphasis on clonality. Our data indicate that stem counts are not effective measures for recovery assessment in these species, and a more complex demographic monitoring protocol should be developed. Additional implications for conservation of these species are discussed, including a consideration for federal listing for Shortia brevistyla.