Discovery of Drosophila melanogaster from Wild African Environments and Genomic Insights into Species History

Abstract

A long-standing enigma concerns the geographic and ecological origins of the intensively studied vinegar fly, Drosophila melanogaster, a globally widespread species [1] which \"has invariably appeared to be a strict human commensal\" [2]. In spite of its sub-Saharan origins, this species has never been reported from undisturbed wilderness environments that might reflect its pre-commensal niche [3]. Here, we document the collection of 288 D. melanogaster individuals from African wilderness areas in Zambia, Zimbabwe, and Namibia. After sequencing the genomes of 17 flies collected from Kafue National Park, Zambia, we found reduced genetic diversity relative to town populations, elevated chromosomal inversion frequencies, and strong differences at specific genes including known insecticide targets. Combining these new genomes with prior data enabled us to gain novel insights into the history of this species geographic expansion. Our demographic estimates indicated that an expansion from southern Africa began approximately 10,000 years ago, with a Saharan crossing soon after, but expansion from the Middle East into Europe did not begin until roughly 1,400 years ago. This improved model of demographic history will provide a critical resource for future evolutionary and genomic studies of this key model organism. Our results add historical context to the species human association, and the opportunity to study wilderness populations opens the door for future studies on the biological basis of its adaptation to human environments.