Shoal Basses, a Clade of Cryptic Identity

Shoal basses are a cryptic clade composed of Micropterus spp. restricted to the Apalachicola River system and three Atlantic slope river drainages in the southeastern US.  This reciprocally monophyletic clade includes the Shoal Bass, Micropterus cataractae Williams and Burgess (endemic to the Apalachicola River system) and an undescribed form from each of the Chattahoochee, Altamaha, and Savannah river drainages.  Members of the shoal bass clade can be distinguished from all other species of Micropterus using 20 diagnostic characters (character attributes, CA) found in ND2 sequences.  Each member of the clade additionally possesses unique CAs, 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 and Altamaha river systems as belonging to a single taxon synonymous with the Redeye Bass, M. coosae, which natively occurs in 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 at least five species, each of which is endemic to a single southeastern drainage.  Introductions of non-native basses, including Spotted basses (M. punctulatus, M. henshalli) and Smallmouth Bass (M. dolomieu) currently threaten the genetic integrity of native shoal bass species in streams of the Chattahoochee, Altamaha and Savannah river systems.  Recognizing and documenting the actual diversity of Micropterus species provides important information for managers and anglers who may wish to avoid stocking or translocations that could further compromise native bass populations.