Effect of dispersal evolution on pre-adult traits in laboratory populations of Drosophila melanogaster

Abstract

Dispersal is a complex spatial process that allows individuals to track favourable environmental conditions. In recent times, with increased incidents of habitat degradation and fragmentation, studies have predicted the evolution of increased dispersal. Given the various causes and costs of dispersal, several traits of an individual are expected to evolve in response to dispersal evolution. Using laboratory populations of Drosophila melanogaster selected for higher dispersal, this study aimed at understanding: (1) how dispersal traits across different life-stages were correlated, (2) the effect of dispersal evolution on pre-adult traits, and (3) how these changes affect the subsequent settlement success in new environments. Additionally, the transmission pattern of dispersal phenotype from parents to offspring was investigated. Results suggest that there was no correlation between adult and larval locomotor activity. The dispersal-selected flies had a lower larval competitive ability than the control flies, and this result was substantiated by a trend of longer development time in dispersal-selected flies and no overall change in body-size. This would imply that dispersers are relatively inefficient at resource-utilization during development, explaining their poor performance in competitive environments. However, despite being competitively inferior in a resource-limited condition, dispersal-selected flies were as successful as control flies with respect to the settlement success in new environments. Lastly, it was found that mother and father did not contribute differentially to the dispersal phenotype of the offspring. The increased dispersal ability of selected populations, combined with no trade-off in proliferative success, makes them potent invaders and colonizers across varied environments.