Molecular phylogeny of Nemadactylus and Acantholatris (Perciformes: Cirrhitoidea: Cheilodactylidae), with implications for taxonomy and biogeography.

The species of Nemadactylus and Acantholatris are perciform fishes with representatives in each ocean of the Southern Hemisphere. Mitochondrial DNA sequences were obtained from all five species of Nemadactylus, two of the three Acantholatris species, and several outgroup taxa. Analysis of cytochrome b sequences placed A. monodactylus and A. gayi within an otherwise entirely Nemadactylus clade, suggesting that these genera are synonymous. The Acantholatris sequences were also very similar to those from three of the Nemadactylus species, despite their geographic separation. Analysis of D-loop sequences paralleled the cytochrome b results, but provided greater resolution of species relationships. Nemadactylus sp. and A. gayi are transoceanic sister taxa. Polytypic clades observed for N. macropterus and A. monodactylus most likely reflect incomplete sorting of mitochondrial DNA lineages. It is proposed that this group dispersed and radiated during the last 0. 6-2.6 million years, and the possible mechanisms of this process are discussed.