Extensive clonal growth and biased sex ratios of an endangered dioecious shrub, Lindera melissifolia (Walt) Blume (Lauraceae)1

Abstract

Plant life history traits like clonal growth and dioecy can complicate endangered species conservation because of the potential for remnant populations to contain few genetically different individuals or a single sex. In this study, we used 11 microsatellite (SSR) markers to characterize fine-scale genetic structure of the endangered dioecious perennial Lindera melissifolia (pondberry) growing in seasonally isolated wetlands across the southern Atlantic Coastal Plain. We found fine-scale genetic structures consistent with extensive clonal growth in all sites. Of the 508 stems sampled across 11 sites, we found 67 genetic individuals (genets), of which 94% were site specific and 39% were represented by a single stem. Individual sites contained from 1 to 16 genets. Spatial genetic analyses showed limited intermingling among different genets within sites, which is consistent with a phalanx clonal growth form. Nine of the eleven sites had biased sex ratios, with six male and three female biased sites. Given our observations of extensive clonal growth, few genetic individuals, and biased sex ratios, we conclude that simple stem counts of this clonal perennial dioecious shrub will grossly overestimate the number of genetic individuals in these remnant southern Atlantic Coastal Plain sites. In order to promote self-sustaining sexually reproducing pondberry populations, as outlined in the pondberry recovery plan, natural areas managers may want to consider introducing unrelated and underrepresented gender plants into sites with few genets or biased sex ratios.