Extreme Population Subdivision in the Crown Conch (Melongena corona): Historical and Contemporary Influences

Organisms with crawl-away larvae are thought to experience highly restricted gene flow. Here, we assess the pattern and magnitude of population subdivision of the direct developing snails in the Melongena corona complex and assess the validity of species and subspecies designations in the genus. A total of 516 individuals from 15 locations were assayed at 8 microsatellite loci. Levels of genetic diversity were moderate and typical of gastropods. There were from 8 to 28 alleles per locus and the average observed per sample heterozygosity ranged from 0.16 to 0.79. Levels of genetic divergence were generally large with all sample pairwise F(ST) values statistically significant and ranging from 0.011 to 0.438 and Jost's D(EST) ranging from 0.028 to 0.731. A Bayesian analysis identified 7 clusters of, usually adjoining, samples. The population subdivision is likely derived from a complex mixture of life-history attributes, frequent short-distance dispersal via swimming larvae, rare short- and long-distance dispersal of rafting larvae and eggs, and a patchwork of adjacent and adjoining habitats. As with a previous study, the current taxonomy is not supported by the genetic results and the complex can be considered as M. corona, a single, albeit clearly geographically genetically structured, species.