Genetic variation and systematic diversity in the ghost shrimp genus Lepidophthalmus (Decapoda : Thalassinidea : Callianassidae)

The resurrected genus Lepidophthalmus defines a group of estuarine burrowin g shrimp, western Atlantic members of which were until recently treated as a single homogeneous species. Individuals from fourteen Gulf of Mexico, two Caribbean, and one eastern Pacific localities were assayed by allozyme ele ctrophoresis of 19 presumptive loci. Results were evaluated by principal co mponents analysis of individual polymorphic allele data for definition of p opulations. Allozyme data were used to compare populations by F-statistics and measurement of pairwise genetic distances. Populations of Lepidophthalm us from within the Gulf of Mexico resolve into three distinct genetic linea ges, pairwise genetic distances of which are comparable to congeneric speci es-level taxa in other invertebrate groups. The most widespread lineage def ines L. louisianensis and consists of all samples from the northern through northwestern Gulf. This species is both geographically and allozymically s eparated from two other lineages (Lepidophthalmus sp. "a" and Lepidophthalm us sp. "b") that occurred sympatrically in a restricted area of the southwe stern Gulf of Mexico, providing the first account of sympatric distribution in the genus. Taxonomic status for the southwestern Gulf lineages remains unresolved, but both are allozymically distinct from the Caribbean congener s, L. jamaicense and L. sinuensis, as well as the eastern Pacific species, L. nr. bocourti.