Molecular systematics of the African electric fishes (Mormyroidea : Teleostei) and a model for the evolution of their electric organs

We present a new molecular phylogeny for 41 species of African mormyroid el ectric fishes derived from the 12S, 16S and cytochrome b genes and the nucl ear RAG2 gene. From this, we reconstruct the evolution of the complex elect ric organs of these fishes. Phylogenetic results are generally concordant w ith earlier preliminary molecular studies of a smaller group of species and with the osteology-based classification of Taverne, which divides the grou p into the Gymnarchidae and the Mormyridae, with the latter including the s ubfamilies Petrocephalinae (Petrocephalus) and Mormyrinae (all remaining ta xa). However, we find that several genera previously recognized by Taverne are non-monophyletic. Within the Mormyrinae, the genus Myomyrus is the sist er group to all the remaining taxa. Other well-supported clades within this group are recovered. A reconstruction of electrocyte evolution on the basi s of our best-supported topology suggests that electrocytes with penetratin g stalks evolved once early in the history of the mormyrids followed by mul tiple paedomorphic reversals to electrocytes with non-penetrating stalks.