Light preference differs between sister species Drosophila americana and D. novamexicana

These data were used to generate a manuscript whose abstract is: Behavioral evolution is an important and understudied component of adaptation to novel environments. Here we investigate behavioral differences in light preference between two allopatrically diverged sister species, Drosophila americana and D. novamexicana. Drosophila americana lives on black willow trees in the eastern United States and has a dark abdominal and thoracic pigmentation while D. novamexicana is found on lighter desert willows in the desert Southwest of the United States and is strikingly light in body color. The genes ebony and tan, which are responsible for the majority of the pigmentation difference between the species, are also known to function in the visual system. We therefore hypothesized that light preference may have diverged between the two species, due either to direct selection for light preference exerted by their differing environments, or as a pleiotropic effect of selection on pigmentation. To test this hypothesis, we performed a behavioral choice experiment using divided fly cages with light and dark habitats. The entire experiment was replicated three times, with sample sizes of 9, 10, and 29 successful trials per experiment. In all trials, more D. novamexicana than D. americana were observed on the light sides of the cages; however, this difference was only statistically significant in the experiment with the largest sample size. While the results differed somewhat across experiments, the data overall indicate that D. novamexicana has a stronger preference for light than D. americana. We suggest that these two recently diverged species are evolving distinct behavioral patterns in response to new environments. Data files show the proportion of flies of each species (out of 10 flies per species per cage) that were observed on the light side of the cage each day. The Temp data file shows the temperatures of the light versus dark sides of two cages.