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 analyzes
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 analyzed the
distribution of anadromous, catadromous, amphidromous, potamodromous and
oceanodromous migratory fish using 1676 species and compared it to 1616
non-migratory fishes. After analyzing 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, where 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 mostly 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