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Aim To investigate the effects of river capture on the biogeographical history of South American freshwater fishes.Location Western Amazon and La Plata basins, and adjacent river drainages. MethodsWe used a species-dense time-calibrated phylogeny of longwhiskered catfishes (Siluriformes, Pimelodidae) to calculate likelihoods for 16 biogeographical scenarios of river capture, each differing in details of (1) landscape evolution and/or (2) models of species range evolution. We designed eight alternative landscape evolution models (LEMs) to represent distinct palaeogeographical river capture histories between the Western Amazon and La Plata drainages during the formation of the Central Andean (Bolivian) orocline (43.0-15.0 Ma). The LEMs differed only in patterns of area-connectivity constraints through time, and otherwise had the same geographical areas, time durations and dispersal probabilities. We used the DEC and DECj models of species range evolution under these eight LEM constraints to calculate likelihood values for ancestral area estimates.Results Divergence time estimates indicated that crown-group pimelodids emerged during the Late Cretaceous or Palaeogene (c. 72.9 AE 20 Ma) and model-selection recovered a best-fit palaeogeographical scenario with (1) a LEM with three river capture events, and (2) a DECj model of species range evolution. These results were quantitatively replicated using Lagrange and BayArea-like methods.Main conclusions The taxon-area chronogram of pimelodids exhibits the characteristic biogeographical signature of river capture; i.e. several non-monophyletic regional (basin-wide) species assemblages coupled with the presence of many species inhabiting more than one basin. These phylogenetic and biogeographical patterns are consistent with the effects of three large-scale river capture events during the formation of the Bolivian orocline.

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Macroevolutionary theory posits three processes leading to lineage diversification and the formation of regional biotas: dispersal (species geographic range expansion), speciation (species lineage splitting), and extinction (species lineage termination). The Theory of Island Biogeography (TIB) predicts species richness values using just two of these processes; dispersal and extinction. Yet most species on Earth live on continents or continental shelves, and the dynamics of evolutionary diversification at regional and continental scales are qualitatively different from those that govern the formation of species richness on biogeographic islands. Certain geomorphological processes operating perennially on continental platforms displace barriers to gene flow and organismal dispersal, and affect all three terms of macroevolutionary diversification. For example, uplift of a dissected landscape and river capture both merge and separate portions of adjacent areas, allowing dispersal and larger geographic ranges, vicariant speciation and smaller geographic ranges, and extinction when range sizes are subdivided below a minimum persistence threshold. The TIB also does not predict many biogeographic and phylogenetic patterns widely observed in continentally distributed taxa, including: (i) power function-like species-area relationships; (ii) log-normal distribution of species geographic range sizes, in which most species have restricted ranges (are endemic) and few species have broad ranges (are cosmopolitan); (iii) mid-domain effects with more species toward the geographic center, and more early-branching, species-poor clades toward the geographic periphery; (iv) exponential rates of net diversification with log-linear accumulation of lineages through geological time; and (v) power function-like relationships between species-richness and clade diversity, in which most clades are species-poor and few clades are species-rich. Current theory does not provide a robust mechanistic framework to connect these seemingly disparate patterns. Here we present SEAMLESS (Spatially Explicit Area Model of Landscape Evolution by SimulationS) that generates clade diversification by moving geographic barriers on a continuous, neutral landscape. SEAMLESS is a neutral Landscape Evolution Model (LEM) that treats species and barriers as functionally equivalent with respect to model parameters. SEAMLESS differs from other model-based biogeographic methods (e.g., Lagrange, GeoSSE, BayArea, and BioGeoBEARS) by modeling properties of dispersal barriers rather than areas, and by modeling the evolution of species lineages on a continuous landscape, rather than the evolution of geographic ranges along branches of a phylogeny. SEAMLESS shows how dispersal is required to maintain species richness and avoid clade-wide extinction, demonstrates that ancestral range size does not predict species richness, and provides a unified explanation for the suite of commonly observed biogeographic and phylogenetic patterns listed above. SEAMLESS explains how a simple ...

We document patterns of coordinated dispersal over evolutionary time frames in heroine cichlids and poeciliine live-bearers, the two most species-rich clades of freshwater fishes in the Caribbean basin. Observed dispersal rate (DO) values were estimated from time-calibrated molecular phylogenies in Lagrange+, a modified version of the ML-based parametric biogeographic program Lagrange. DO is measured in units of “wallaces” (wa) as the number of biogeographic range-expansion events per million years. DO estimates were generated on a dynamic paleogeographic landscape of five areas over three time intervals from Upper Cretaceous to Recent. Expected dispersal rate (DE) values were generated from alternative paleogeographic models, with dispersal rates proportional to target area and source-river discharge volume, and inversely proportional to paleogeographic distance. Correlations between DO and DE were used to assess the relative contributions of these three biogeographic parameters. DO estimates imply a persistent dispersal corridor across the Eastern (Antillean) margin of the Caribbean plate, under the influence of prevailing and perennial riverine discharge vectors such as the Proto–Orinoco–Amazon river. Ancestral area estimation places the earliest colonizations of the Greater Antilles and Central America during the Paleocene–Eocene (ca. 58–45 Ma), potentially during the existence of an incomplete Paleogene Arc (∼59 Ma) or Lesser Antilles Arc (∼45 Ma), but predating the GAARlandia land bridge (∼34–33 Ma). Paleogeographic distance is the single best predictor of DO. The Western (Central American) plate margin did not serve as a dispersal corridor until the Late Neogene (12–0 Ma), and contributed relatively little to the formation of modern distributions.