Migratory lineages rapidly evolve larger body sizes than non-migratory relatives in ray-finned fishes

Migratory animals respond to environmental heterogeneity by predictably moving long distances in their lifetime. Migration has evolved repeatedly in animals, and many adaptations are found across the tree of life that increase migration efficiency. Life history theory predicts that migratory species should evolve a larger body size than non-migratory species and some empirical studies have shown this pattern. A recent study analyzed the evolution of body size between diadromous and non-diadromous shads, herrings, anchovies and allies, finding that species evolved larger body sizes when adapting to a diadromous lifestyle.  It remains unknown whether different fish clades adapt to migration similarly.  We used an adaptive landscape framework to explore body size evolution for over 4500 migratory and non-migratory species of ray-finned fishes. By fitting models of macroevolution, we show that migratory species are evolving towards a body size that is larger than non-migratory species. Furt...