Abstract
Ghost shrimps (Decapoda: Callianassidae) are common estuarine and marine burrowing organisms of tropical to temperate waters, typically found in intertidal to shallow subtidal habitats. Except for an abbreviated planktonic larval phase, most callianassids live as obligate burrowers and appear to depend on the burrow for shelter, reproduction, and feeding. Recent studies have shown the genus Lepidophthalmus, a group largely restricted to estuaries and river mouths, to be surprisingly speciose, but relationships among these taxa and driving forces for their separation remain poorly understood. We include fifteen described species of Lepidophthalmus in a molecular phylogenetic analysis based upon sequence analyses of the 16S and 12S mitochondrial genes. Our findings clarify the monophyletic membership of the genus and confirm postulated species separations. We reconfirm validity of Lepidophthalmus eiseni, reject two recently proposed new genera for selected members of Lepidophthalmus, and define ecologically and morphologically informative clades among congeners. Limited capability for larval dispersal and regional biogeographic history could well account for high diversity and regional endemism observed within the genus. Biogeographic scenarios, including continental drift, closure of the Panamanian Isthmus, and post-glacial dispersals, are invoked to account for proposed reconstructions of historical relationships.