Comparative morphology, phylogeny and classification of African seasonal killifishes of the tribe Nothobranchiini (Cyprinodontiformes: Aplocheilidae)

Abstract

A comparative morphological study of 42 species of the African tribe Nothobranchiini provided 138 characters that, combined with available DNA sequences (3327 bp), highly supported monophyly of the tribe, making it possible to generate the first unambiguous diagnoses for included genera (Fundulosoma, Pronothobranchius and Nothobranchius). The analyses corroborate Fundulosoma as the sister group to a clade containing all other Nothobranchiini. This study first reports a broad diversification of jaw and branchial structures in Nothobranchius, the most diverse aplocheiloid genus, traditionally divided into subgenera. Six subgenera are recognized (Adiniops, Cynobranchius subgen. nov., Nothobranchius, Paranothobranchius, Plesiobranchius subgen. nov. and Zononothobranchius). Cynobranchius is erected for a clade of deep-bodied, zooplankton-feeding species, diagnosed by 16 morphological synapomorphies, of which nine are probably related to their specialized feeding habits. The clade containing Cynobranchius and the monotypic subgenus Plesiobranchius is supported as the sister group to a clade containing all other subgenera of Nothobranchius. Paranothobranchius, comprising the largest aplocheiloid species, is diagnosed by 17 apomorphic conditions, most of them related to specialized piscivorous habits. However, this study indicates that predator jaw morphology arose independently three times in Nothobranchius. Aphyobranchius, formerly including specialized surface-dwelling species, is considered to be a synonym of Adiniops.