Genetic mosaicism and population connectivity of edge-of-range Halodule wrightii populations

The genetic population structure of Halodule wrightii at locations in Florida, North Carolina, and Bermuda was investigated using 11 polymorphic microsatellite loci on samples representing 15 sites. We measured allelic diversity and genotypic richness and determined population differentiation and gene flow using principal components and k-means population clustering. Halodule wrightii sites were highly clonal with a mean genotypic richness of 0.09. Genetic differentiation followed a statistically significant isolation-by-distance relationship. Population clustering identified two groups 1) Bermuda and Florida Bay, and 2) the Indian River Lagoon, Gulf of Mexico, and North Carolina. Results from this study indicate that vegetative growth is important for H. wrightii at multiple spatial scales and that isolated populations of H. wrightii likely originated from founder effects. In addition, many of the identified clones included samples that displayed variable copy number of some loci, suggestive that there may be an abnormal chromosome complement and/or may be indicative of aneuploidy. Given the low genotypic diversity observed overall, genetic diversity accumulated without sexual reproduction through genetic mosaicism and other derived somatic mutations will affect fitness and clonal persistence.