Time-calibrated molecular phylogeny reveals a Miocene–Pliocene diversification in the Amazon miniature killifish genus Fluviphylax (Cyprinodontiformes: Cyprinodontoidei)

Species of Fluviphylax are widely distributed over the Amazon and Orinoco river drainages and are among the smallest fish in the neotropics, inhabiting areas near the margin of slow-flowing clear and black water streams and lakes. Here, we present the first multigene molecular phylogeny of Fluviphylax, including all five nominal species of Fluviphylax and three undescribed species. The analysis included fragments of one mitochondrial and five nuclear genes, totaling 5880 bp. The dataset was analyzed using maximum parsimony, maximum likelihood, and Bayesian inference approaches providing high-supported well-solved trees. A time-calibrated analysis was performed providing information on the origin and diversification of the miniature genus in the Amazon. We estimate that Fluviphylax lineage splits from its sister group, the Anablepidae and Poeciliidae (Poeciliinae sensu Parenti, 1981), during the Late Eocene, about 36.6 Mya; but lineage diversification started only in the Middle Miocene, about 16 Mya, during the formation of the Pebas system. Subsequent splits within Fluviphylax occurred in the Late Miocene–Pliocene, between 10 and 6 Mya and during the Pliocene, and were probably influenced by paleogeographical events such as the breaching of the Purus arch, the rise of the Vaupés arch, the uplift of the Fitzcarrald arch, and the capture of the Contigo and Uraricoera river drainages by the Branco River. The present time-calibrated analysis provides the first insight on the evolution of one of the smallest vertebrate taxa in the Amazon and Orinoco river drainages.