The distribution of vineyard populations of Drosophila melanogaster and Drosophila simulans during vintage and non-vintage periods.

Field studies inside and outside the cellars of the "Chateau Tahbilk" vineyard have substantiated the distribution data of original collections. D. melanogaster is found inside and outside the cellars while D. simulans is only collected outside. The presence of alcohol fumes in the outside environment during vintage alters the distribution of the species, relative to non-vintage periods, with D. melanogaster being closer to the source. Mark-release-recapture experiments suggest that movement by the species towards and away from an alcohol associated resource could explain this result. That is, the behavioural patterns of the species are differentially affected by the presence of alcohol in the environment.The distribution of the sexes of D. melanogaster may depend on their relative physiological tolerance to the presence of alcohol in the environment. The excess of females in the cellar and close to the fermentation area during vintage is due to the increased mortality of males in these areas. The reason for the distribution of the sexes of D. simulans during vintage, when an excess of females is found farthest from the fermentation area, remains speculative, but may involve behavioural mechanisms.