Discordant patterns of morphological and molecular change in broadtail madtoms (genus Noturus)

Two morphologically distinct forms of an undescribed madtom catfish (Noturu s sp.) occur in the rivers and lakes of southeastern USA. 'Lake' broadtail madtoms are endemic to Lake Waccamaw and are probably related to nearby 'ri ver' broadtail populations. To investigate phylogenetic relationships, we s urveyed mitochondrial DNA (mtDNA) sequence Variation in 'lake' and 'river' broadtails and other members of the genus Noturus. Mitochondrial rDNA data suggest a sister group relationship between broadtail madtoms and N. insign is, not N. leptacanthus as posited previously. Population-level analyses us ing additional mtDNA characters (NADH dehydrogenase subunit 2 (ND2) and cyt ochrome b (Cytb)) identified two highly divergent genetic lineages within b roadtail madtoms that do not correspond to the morphological designations ' river' and 'lake'.