Drosophilid Species (Diptera) in the Brazilian Savanna Are Larger in the Dry Season

Recently, interest in the effects of global climate change on biological communities has grown substantially. Both historical records and model predictions indicate that temperatures and aridity will likely increase in the continental interiors, although the effects of increased aridity have been less studied. The Brazilian savanna has a strong annual dry season, during which time drosophilid populations experience bottlenecks. In this study, we monitored a drosophilid assemblage in the core area of the Brazilian savanna throughout 1 yr. We then compared fly wings collected in the dry and rainy seasons for two common drosophilid species, Drosophila mercatorum Patterson & Wheeler and Drosophila simulans Sturtevant. Drosophilid abundance and richness decreased significantly in the dry season, confirming previous findings. In addition, although no significant differences in wing shape were observed for flies collected during the two seasons, the wing size of both focal species was significantly higher in the dry season. Considering the reported association between Drosophila Fallen wing size and body size, we deduced that the flies were larger in the dry season. D. mercatorum and D. simulans were also found at higher relative abundances in the dry season, when most species were not collected in the field. The observed difference in wing size could have been the result of biotic or abiotic factors, such as larval density and climate. More efforts are necessary to untangle the factors that lie behind this pattern, but it is possible that increased size is an advantageous trait when struggling against dry conditions.