Physiological vagility affects population genetic structure and dispersal and enables migratory capacity in vertebrates

Vagility is defined as the relative capacity for movement. We developed previously a quantitative metric in vertebrates for physiological vagility (PV), the speed at which an animal can move sustainably, incorporating aerobic capacity, body size, body temperature, and transport costs, allowing quantitative tests of whether PV can explain variation in interclass population genetic structure and behaviors involved in dispersal. We found that PV increased with body mass, correlated with maximal dispersal distances, and was inversely related to genetic structure in multiple vertebrate groups. Here we review these relationships and expand our analysis to include additional groups; we also suggest that PV may be utilized to partially explain variation in migratory capacity between groups. We show a positive correlation between PV and maximum migration distance (MMAX) in most groups that reflects many of the relationships observed between PV and dispersal. Flying birds, marine mammals, and large terrestrial mammals display the greatest MMAX and each of these groups has the highest PV among vertebrate groups, while reptiles and small terrestrial mammals had the lowest PV and MMAX. By contrast, marine turtles have exceptional MMAX but do not possess high PV. We suggest that PV is an important mechanism enabling both dispersal and migratory capacity, and affects genetic structure, but that other life history characteristics also need to be considered.