Diversity of visuomotor reflexes in two Drosophila species

For adaptive behavior, an organism must identify and assign subjective value to salient sensory information, but what stimuli are salient could change depending upon the local features of the environment. Insects such as fruit flies (Drosophila), for example, rely on olfactory cues to locate food and oviposition sites. But not all Drosophila species find the same stimuli to be salient: for example, four geographically isolated populations of Drosophila mojavensis, which feed and oviposit on necrotic cacti, show olfactory-driven behavioral preferences for host cacti specific to the local environment of each population [1,2]. We wondered whether visual features specific to certain environments could drive divergent visuomotor responses. We compared the visuomotor reflexes of D. melanogaster, a cosmopolitan generalist found in moderately dense visual environments, with D. mojavensis, a cactophilic specialist found in comparatively sparse visual landscapes. We found that, like D. melanogaster, D. mojavensis steer towards long vertical stripes, such as landscape features [3], but in contrast to D. melanogaster's aversion to small objects [3], D. mojavensis find small objects attractive or of neutral value.