Spatial Distribution and Dispersal in a Population of Drosophila

Spatial distribution in a Drosophila engyochracea population in Kipuka Ki (island of Hawaii) is nonuniform. Density of flies was highest close to a known breeding site, and sex ratio is also different in the two sides of the road that crosses Kipuka Ki. Females are more attracted to banana baits than males. Flies disperse easily all over the experimental area. The road acts as a small barrier to dispersal, especially for males. Data suggest that females move more freely than males, but the evidence is poor. Nevertheless, it is safe to say at least that males do not disperse farther and easier than females. Migration rates and population sizes have been estimated using a modified Lincoln-Pearson mathematical model and allowing several restrictive conditions. The study area was calculated to have an actual population size (N) of approximately of 40,000, or about 5.4 flies per square meter. The spatial distribution and dispersal of D. engyochracea have important implications in population parameters. Namely, effective population size (Ne) is not much influenced by difference in sex numbers, but it is presumably influenced by the unequal distribution of sexes in the population area.