The Macroecology Of Fish Migration

Aim We still lack a consensus on the main variables driving changes in migratory strategies. Different hypotheses have been proposed: productivity, energy, environmental heterogeneity, and genetic predisposition. This work takes an integrative view and analyses migrations from a macroecological perspective estimating the extent to which different environmental variables and historic factors influence migratory life histories.Location Global.Time period Current.Major taxa studied Actinopterygian fishes.Methods Using public domain museum records, global repositories, and global measures of temperature, productivity, precipitation and heterogeneity, we spatially analysed the distribution of anadromous, catadromous, amphidromous, potamodromous and oceanodromous migratory fish using 1,676 species and compared it to 1,616 non-migratory fishes. After analysing the individual roles of productivity and temperature in shaping biodiversity, we conducted path analyses including several environmental variables and principal coordinates of phylogenetic structure (PCPS).Results The different migratory strategies are not evenly distributed around the globe and phylogeny is a relevant variable in shaping current patterns. Productivity is positively related to species richness, except for anadromy and potamodromy, for which we observed a unimodal curve. Temperature significantly drives migratory species richness (except for anadromy). The role of environmental heterogeneity, measured as temperature seasonality and annual range, is strongest for anadromous species, which helps explain their skewed distribution towards higher latitudes and why the kinetic energy hypothesis fails in explaining their richness patterns.Main conclusions Overall, migratory fish richness can be explained by the interaction of multiple variables, such as productivity, temperature, environmental heterogeneity, and the role of phylogeny, but these variables interact differentially in each strategy, diverging most for the anomalous anadromous fishes. Integrating these results into a global framework to better understand the evolutionary and ecological dynamics of migration will help with predicting responses to anthropogenic climate change.