Abstract
Over half of all vertebrates are “fishes”, which exhibit enormous diversity in morphology, physiology, behavior, reproductive biology, and ecology. Investigation of fundamental areas of vertebrate biology depend critically on a robust phylogeny of fishes, yet evolutionary relationships among the major actinopterygian and sarcopterygian lineages have not been conclusively resolved. Although a consensus phylogeny of teleosts has been emerging recently, it has been based on analyses of various subsets of actinopterygian taxa, but not on a full sample of all bony fishes. Here we conducted a comprehensive phylogenetic study on a broad taxonomic sample of 61 actinopterygian and sarcopterygian lineages (with a chondrichthyan outgroup) using a molecular data set of 21 independent loci. These data yielded a resolved phylogenetic hypothesis for extant Osteichthyes, including 1) reciprocally monophyletic Sarcopterygii and Actinopterygii, as currently understood, with polypteriforms as the first diverging lineage within Actinopterygii; 2) a monophyletic group containing gars and bowfin (= Holostei) as sister group to teleosts; and 3) the earliest diverging lineage among teleosts being Elopomorpha, rather than Osteoglossomorpha. Relaxed-clock dating analysis employing a set of 24 newly applied fossil calibrations reveals divergence times that are more consistent with paleontological estimates than previous studies. Establishing a new phylogenetic pattern with accurate divergence dates for bony fishes illustrates several areas where the fossil record is incomplete and provides critical new insights on diversification of this important vertebrate group.
Highlights
Freshwater fishes are a fundamental component of the biosphere, constituting more than 20% of living vertebrate species (Nelson, Grande & Wilson, 2016)
We provide the following estimates for the origin times of these clades: Lepidosireniformes [125–95 million years ago (Ma)]; total-group Osteoglossomorpha (207–167 Ma); Characiformes (120–95 Ma; a younger estimate of 97–75 Ma when controversial Cenomanian fossils are excluded); Galaxiidae (235–21 Ma); Cyprinodontiformes (80–67 Ma); Channidae (79–43 Ma); Percichthyidae (127–69 Ma)
Extant freshwater fish clades with intercontinental, disjunct distributions have long been model systems in historical biogeography, as seas and oceans represent a relatively strong barrier to their dispersal (Lundberg, 1993)
Summary
Freshwater fishes are a fundamental component of the biosphere, constituting more than 20% of living vertebrate species (Nelson, Grande & Wilson, 2016). Our method is based on the number and distribution through time of known stratigraphic horizons that yielded fossils belonging the group of interest This approach builds upon the theoretical framework developed by Marshall (1997), which accounts for non-uniform fossil preservation and recovery through time by using an empirically derived function of recovery potential. The beginning of the Permian (around 299 Ma) was chosen as the upper limit for the age of fossil horizons: this represents the prior upper bound on the Bayesian estimates for the origin times of the focal clades This is a conservative prior, as it does not artificially exclude vicariance scenarios; the oldest fossils belonging to the analysed clades come from the Middle Jurassic (around 167 Ma).
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