Desiccation resistance and mating behavior in laboratory populations of Drosophila simulans originating from the opposing slopes of Lower Nahal Oren (Israel)

Lower Nahal Oren in Northern Israel, often referred to as "Evolution Canyon", has been proposed as a microscale model site for ecological evolution. However, conflicting mating assay and stress-resistance contribute to controversy over the Nahal Oren model. In this study we further tested the Nahal Oren model, while extending its focus from Drosophila melanogaster to its sister species, D. simulans. Using fly populations derived from the opposing canyon slopes and acclimated to laboratory conditions for 11-22 generations we did not find a significant slope effect on desiccation resistance (p=0.96) or body metabolic fuel content (p>0.43) which would indicate a genetic basis for adaptation to local resource limitation. Multiple-choice mating assays (47-48% homotypic couples in two replicate populations) did not indicate divergence from a random mating pattern between north and south-facing slope flies. In conclusion, our findings do not support divergence of D. simulans populations across Lower Nahal Oren.