Genetic analysis of Drosophila melanogaster in the French West Indies and comparison with populations from other parts of the world

Abstract

Four natural populations of Drosophila melanogaster, three from Guadeloupe and one from Martinique (French West Indies), were studied with respect to four types of genetically determined traits, namely allozyme frequencies, morphology, ethanol tolerance, and oviposition rhythm. These populations were compared to European (France) and tropical African populations, and, with respect to allozymes alone, to an American population. The four populations from the West Indies were found to be genetically similar; this may reflect a common historical origin, or an adaptive response to similar environmental pressures or possibly some gene flow between the two islands. The comparisons with distant populations led to different conclusions depending upon the trait considered. In the case of allozymes, flies from the West Indies were more similar to tropical African populations than to an American population from Texas, but the main difference observed was in comparison with European populations. The morphology of the West Indies flies resembled a smaller, tropical type, but the size was even smaller than observed in Africa. Both ethanol tolerance and oviposition rhythm were intermediate between flies from tropical Africa and Europe. All these results can be explained in terms of interactions between selection imposed by a tropical environment and the genetic properties of the founder population which first colonized the islands.