Shoal Basses: A Clade of Cryptic Identity
Byron J. Freeman, Andrew T. Taylor, Kenneth J. Oswald, John Wares, Mary C. Freeman, Joseph M. Quattro, and Jean K. Leitner
Abstract.—Shoal basses are a cryptic clade composed of Micropterus spp. restricted to the Apalachicola River system and three southeastern Atlantic slope river drainages in the southeastern United States. This reciprocally monophyletic clade includes the Shoal Bass M. cataractae (endemic to the Apalachicola River system), the Chattahoochee Bass M. chattahoochae, and two undescribed forms from the Altamaha, Ogeechee, and Savannah River drainages. Members of the shoal bass clade can be distinguished from all other species of Micropterus basses using 20 diagnostic characters (characteristic attributes) found in mitochondrial DNA (NADH dehydrogenase subunit 2) gene sequences. Each member of the clade additionally possesses unique characteristic attributes, which along with morphological and meristic characters can be used to diagnose this cryptic biodiversity. Biologists and managers have previously regarded the shoal basses in the Chattahoochee, Savannah, Altamaha and Ogeechee River systems as belonging to a single taxon synonymous with the Redeye Bass M. coosae, which is endemic to the Mobile River drainage. With these and previous analyses (including description of the Shoal Bass), we now recognize that what was once considered a single taxon actually comprises seven species, each of which is endemic to a single southeastern drainage. Recognizing and documenting the actual diversity of Micropterus spp. provides important information for managers who may wish to avoid stocking or translocations that could compromise the genetic integrity of native bass populations. Introductions of nonnative basses, including Alabama Bass M. henshalli, Spotted Bass M. punctulatus, and Smallmouth Bass M. dolomieu currently threaten the integrity of native shoal bass species in streams of the Chattahoochee, Altamaha, Ogeechee, and Savannah River systems.