Nutrition and density dependence of spontaneous female-biased dispersal inDrosophila melanogaster

Dispersal is often essential for the attainment of Darwinian fitness, especially for species living on spatially structured, heterogeneous habitats. Theoretically, sex-specific resource requirement can drive the two sexes to disperse differently, resulting in sex biased dispersal (SBD). Understanding ecological factors affecting SBD is important. Using an experimental two-patch dispersal setup we measured spontaneous dispersal in laboratory adapted populations of Drosophila melanogaster under a set of common, interlinked ecological scenarios relating to – (a) dietary ecology and (b) adult density. We found deteriorating overall nutritional quality of food affects strength of SBD, and female dispersal is particularly sensitive to availability of protein. Adult density had sex specific effect on dispersal. Female dispersal was found to be density independent but males showed increased dispersal at higher density. Female tend to disperse more from male biased patch likely to avoid male harassment whereas absence of female drives male dispersal solidifying mate-finding dispersal hypothesis. These evidences of dispersal suggest that variation in dietary ecology and intraspecific competition can affect the degree and strength of existing SBD and thereby male-female interactions in a patch potentially affecting fitness components and population dynamics.