Larval swimming capacities affect genetic differentiation and range size in demersal marine fishes

Dispersal is a fundamental process governing the ecological and evolutionary dynamics of any given species. Due to inherent challenges associated with measuring dispersal directly, identifying proxies for dispersal capacity has long been an active field of research across ecosystems. In marine systems, pelagic larval duration (PLD) has been one of the most widely used indicators of interspecific dispersal potential. The validity of this proxy, however, relies mostly on the assumption of entirely passive dispersal, a notion that has been challenged by findings of strong larval behavioural capabilities. Here, we assessed the effect of larval swimming capacities measured as mean critical swimming speed (U-crit) on emergent species-level properties related to dispersal potential, population genetic structure and global range size, in demersal marine fishes. In a meta-analytic framework, we tested the relative importance of U-crit versus other in trinsic (PLD, egg type, adult body size) and extrinsic (genetic marker type, study scale) predictors of isolation-by-distance slope, global FST and range size. U-crit showed stronger relationships with all emergent response variables than PLD and was consistently the most important predictor in multi-model inference. Our findings indicate that larval swimming capacities could serve as a powerful indicator of a species' long-distance dispersal potential.