Genotypic diversity and clonal structure of everglades sawgrass, Cladium jamaicense (Cyperaceae)

The extent of asexual reproduction and the spatial distribution of clones can influence ecological and evolutionary processes in populations. Sawgrass, Cladium jamaicense, which is the dominant ecosystem component in the Florida Everglades, can reproduce sexually and asexually. We examined patterns of genotypic diversity and evaluated the importance of clonal reproduction in Everglades populations of C. jamaicense, using allozymes as genetic markers. We sampled plants in a replicated grid along 11-m transects in 18 populations of sawgrass distributed throughout the Everglades. Genotypic diversity was low in Everglades sawgrass populations, compared with other plants (mean [SE] number of multilocus genotypes per population = 4.9 [0.7]), but only one population was monomorphic. Diversity was present even at a small scale; 85 of 108 1-m(2) quadrats had more than one multilocus genotype. South Florida water management areas did not differ with respect to genotypic diversity, except for Everglades National Park, which had populations with a smaller proportion of polymorphic quadrats. Sawgrass clones were closer together than nonclones on average, although this varied among populations. Despite this observation, we found little evidence for spatial structuring of clones using the method of probability of clonal identity. This result reflected the broad interdigitation of clones along transects. Estimated mean (SE) minimum clone size was 46.2 (5.2) m(2) and clones may reach over 200 m(2). Our results indicate that asexual reproduction is common in C. jamaicense populations but that genotypic diversity is maintained throughout the ecosystem, even at relatively small scales.