From wings to tails: a general framework for inferring dispersal potential from morphology

Abstract

Dispersal shapes gene flow, range dynamics, and extinction risk, yet direct measures of dispersal are unavailable for most taxa. Here, we test whether the aspect ratio of propulsive surfaces, an established proxy in birds, provides a general morphological basis for inferring dispersal potential. Using sharks as a model taxa, we find caudal fin aspect ratio was positively associated with swimming speed and geographic range size. Applying this proxy across 452 species, we find no evidence of a latitudinal gradient in dispersal potential, in contrast to dispersal patterns reported for birds, due to the lack of a direct effect of environmental temperature on the geographic distribution of caudal fin aspect ratio. Higher dispersal potential was associated with pelagic habitats, larger body size and greater oxygen uptake capacity. Because aspect ratios can be measured from museum specimens and illustrations, this approach could enable comparisons of dispersal potential across air- and water-dwelling vertebrates.