Interaction and integration among behaviors of adult Drosophila in nature.

Abstract

Living in environments whose ecologies vary in periods as short as 24 h is a challenge for animals as Drosophila species that inhabit pear and apple orchards. These orchards have sunny and shady sections. The size and shape of these habitats change daily according to the position of the sun in the sky. Sunny areas are related to dryness and water loss, and shady places have lower temperatures and higher humidity. The presence of heterospecific flies may lead to competition for space and food. In sunny habitats we did not find adult Drosophila. In shady sections we found conspecific groups D. melanogaster, D. simulans, D. immigrans, D. subobscura, and the Chilean endemic D. pavani perched on grasses and herbs at 8-10 cm from fruits that had fallen on the ground. In the fruits, 99% of the adults were females and they were not grouped. The way in which daily changes in the size and shape of shady habitats together with the presence of heterospecific adults influence the selection of places to live is poorly understood in Drosophila. Our experiments show that adults of the five species prefer dark areas. The experimental results show that the odors of each species: i) influence conspecifics to select similar perch sites and decrease mobility, and ii) increase mobility in heterospecific adults and modify their perch site preferences. Attractions between conspecifics, the repulsions between species, and preferences for shaded areas matter in choosing a place to live in the five Drosophila species. These behaviors seem to have evolved as coordinated routines, contributing to the coexistence of the five Drosophila species in the apple and pear orchards examined.