Pupation site preference (PSP) variation in cold adapted, warm adapted, and generalist Drosophila species

Abstract

The larval pupation site preference (PSP) of five Drosophila species belonging to three groups: cold-adapted (Drosophila nepalensis and D. simulans), warm-adapted (D. ananassae and D. virilis), and generalist (D. melanogaster) were analysed in laboratory conditions relative to both humidity and temperature. Our results showed that PSP differ significantly under different humid conditions. Irrespective of temperature, in dry conditions (40% humidity) larvae preferred to pupate on food (97% in cold adapted species and 60% in warm adapted species) whereas in wet conditions (80% humidity), larvae preferred to pupate away from food (58% in cold adapted species and 85% in warm adapted species). Drosophila melanogaster being a generalist species switched its PSP on-fruit to off-fruit from low to high humidity, respectively. We observed high digging behavior (99% diggers) in larvae of cold adapted species whereas warm adapted species exhibited low digging behavior (44% diggers). These results suggest that humidity along with digging behavior are the major factors affecting the PSP in Drosophila species.