Selection for greater dispersal in early life increases rate of age-dependent decline in locomotor activity and shortens lifespan

Locomotor activity is one of the major traits that is affected by age. Greater locomotor activity is also known to evolve in the course of dispersal evolution. However, the impact of dispersal evolution on the functional senescence of locomotor activity is largely unknown. We addressed this knowledge gap using large outbred populations of Drosophila melanogaster selected for increased dispersal. We tracked locomotor activity of these flies at regular intervals until a late age. The longevity of these flies was also recorded. We found that locomotor activity declines with age in general. However interestingly, the activity level of dispersal-selected populations never drops below the ancestry-matched controls, despite the rate of age-dependent decline in activity of the dispersal-selected populations being greater than their respective controls. The dispersal-selected population was also found to have a shorter lifespan as compared to its control, a potential cost of elevated level of activity throughout their life. These results are crucial in the context of invasion biology as contemporary climate change, habitat degradation, and destruction provide congenial conditions for dispersal evolution. Such controlled and tractable studies investigating the ageing pattern of important functional traits are important in the field of biogerontology as well.