Molecular phylogeny of the ghost knifefishes (Gymnotiformes: Apteronotidae)

Abstract

Ghost knifefishes (Gymnotiformes: Apteronotidae) are weakly electric fishes that possess a high-frequency, neurogenic electric organ discharge. They are found throughout the humid Neotropics from Panama to Argentina and are most diverse and abundant in the channels of large lowland rivers. Apteronotidae is the most species-rich family of Neotropical electric knifefishes with 96 valid species in 15 genera. We present a phylogenetic hypothesis based on molecular sequence data from three mitochondrial genes (16S, coi, cytb) and four nuclear loci (glyt, rag2, ryr3, zic1). Our analysis includes sequence data for 203 samples in 54 species and 14 genera, making it the most densely-sampled and data-rich phylogeny of the Apteronotidae to date. Our results corroborate previous phylogenetic hypotheses with the placement of Orthosternarchus + Sternarchorhamphus sister to all other apteronotids, a non-monophyletic Apterontotus, and a sister relationship between Sternarchorhynchus and the Navajini. We also report several novel relationships, particularly within the Navajini and among several species of the nominal genus Apteronotus not previously included in phylogenetic analyses. We additionally provide a new classification for the family.