Rapid wing size evolution of African fig fly (Zaprionus indianus) following temperate colonization

Invasive species often encounter novel selective pressures in their invaded range, and understanding their potential for rapid evolution is critical for developing effective management strategies. Zaprionus indianus is an invasive drosophilid native to Africa that reached Florida in 2005 and likely re-establishes temperate North American populations each year. We addressed two evolutionary questions in this system: first, do populations evolve phenotypic changes in the generations immediately following colonization of temperate environments? Second, does Z. indianus evolve directional phenotypic changes along a latitudinal cline? We established isofemale lines from wild collections across space and time and measured twelve ecologically relevant phenotypes, using a reference population as a control. Z. indianus evolved smaller wings following colonization, suggesting early colonizers have larger wings, but smaller wings are favorable after colonization. No other phenotypes changed significantly following colonization or across latitudes, but we did see significant post-colonization changes in principal components of all phenotypes. We documented substantial laboratory evolution and effects of the laboratory environment across multiple phenotypes, emphasizing the importance of controlling for both possibilities when conducting common garden studies. Our results demonstrate the potential for rapid adaptation in Z. indianus, which could contribute to its success and expansion throughout invaded ecosystems.

Methods
Fitness-related and morphological phenotypes were measured for lab-reared Zaprionus indianus flies derived from wild-caught flies. We started isofemale lines from flies collected at different times and locations and compared the phenotypes of those lines. The data archived here include the raw phenotypic measurements and relavent metadata about each sample, as well as processed data including line means. The code for analysis and plotting is also included. See Gray, Rakes, et al for detailed methodological information.