Tracking Dispersal Across A Patchy Landscape Reveals A Dynamic Interaction Between Genotype And Habitat Structure

Theoretical and empirical studies often show that within populations, individuals vary in their propensity to disperse. We aspired to understand how this behavioural variation is impacted by the distribution and pattern of food patches across a landscape. In a series of experiments we examined how inter-patch distance and the distribution of food patches influenced dispersal in wild-type strains ofDrosophila melanogasterwith natural allelic variants of theforaging(for) gene known to influence dispersal in this species. The 'rover' strain was homozygous for thefor(R)allele (more dispersive) whereas the 'sitter' strain was homozygous forfor(s)(less dispersive). We also assessed an outbred population of flies with an unknown dispersal propensity. Dispersal was assayed in a multi-patch lab arena (25 cells, 5 x 5 array). In the inter-patch distance trials, landscapes of two different sizes (small versus large) were used, both with food in all 25 cells. Dispersal was reduced in the large landscape relative to the small landscape for all three fly strains. Sitter dispersal was lowest relative to both rovers and the outbred flies, whose dispersal tendencies were similar. In the patch distribution trials, flies were assayed in landscapes with varying distribution and number of cells containing food. Dispersal generally increased as the number of patches with food increased, however, rovers and sitters adopted similar dispersal strategies when food was fixed and limited. Conversely, their strategies differed when the total amount of food increased with the number of patches. We find that both the inter-patch distance and distribution can influence dispersal. However, the effect of inter-patch distance and distribution on dispersals depends on genotype x environment interaction. Our findings highlight the importance of considering G x E when assessing how dispersal strategies and landscape dynamics influence the distribution of animal communities.