Bigger isn't always better: body size, developmental and parental temperature and male territorial success in Drosophila melanogaster

Abstract

The effect of developmental temperature (18°C versus 25°C) on the body size and territorial success of male fruit flies, Drosophila melanogaster, in paired contests was examined. When tested at ambient temperatures of either 18°C or at 27°C, adult males raised at 25°C were relatively small in size but nevertheless had greater territorial success (control of a food/oviposition resource) than males raised at 18°C. This result negates a ‘size-advantage hypothesis’, which predicts that males raised at 18°C should be more successful at either contest temperature by virtue of their larger size. It also negates an ‘acclimation-advantage hypothesis’, which predicts that males raised at 18°C should be more successful than males raised at 25°C in contests at 18°C, but less successful at 27°C. The data are consistent, however, with an ‘optimal developmental temperature hypothesis’, which suggests that flies raised at 25°C, even though phenotypically small, are physiologically vigorous and will perform relatively well under diverse environmental circumstances. Thus, bigger isn't always better. In a small-scale experiment territoriality scored only at 27°C) in which all males had the same developmental temperature (25°C) males whose parents developed at 25°C were more successful than were males whose parents developed at 18°C. These experiments demonstrate that developmental temperatures, both within and between generations, influence territorial success in male flies.