The global geography of fish diadromy modes

Aim: Geographical gradients in resource production are likely to translate into macro-ecological patterns in the biodiversity of migratory organisms but few studies have addressed this question at a global scale. Here we tested a hypothesis based on uncoupled latitudinal gradients in marine and freshwater primary productivities aimed at explaining where (e. g. at which latitude) and at which stage of the life cycle (larvae: amphidromy, juvenile: catadromy, adult: anadromy) migration from ocean to freshwater occurs (diadromy). Location: Global. Time period: Current. Major taxa studied: Fishes. Methods: We modelled, using multinomial regressions, the proportion of catadromous, anadromous, and amphidromous species in 994 river basins as a function of freshwater and marine net primary productivities (NPP, mgC/m²/day) and additional biotic and abiotic variables. Using data extracted from GBIF we tested whether diadromous, catadromous and amphidromous species differed with respect to the NP...