Comparative population structuring of molecular and allozyme variation ofDrosophila melanogaster Adhbetween Europe, West Africa and East Africa

Abstract

Restriction enzyme molecular variation in Drosophila melanogaster Adh was compared between three natural populations from Europe, West Africa and East Africa. The frequency distribution of silent variation in the slow allele was compatible with the neutral model in all three samples. The number of haplotypes in East Africa was significantly higher than in the other two populations. The largest divergence, as measured by ^t, was between the East African population and a group made up from the West African, the European, and previously studied American populations. We suggest that a split first occurred within African populations at least 44000 years ago. European populations separated from West Africa more recently, between the last glacial maximum and the post-glacial optimum, 18000 to 8000 years ago. We suggest that this species was domesticated recently relative to human evolution, possibly with the advent of agriculture. Population differentiation with respect to the two allozymes, fast and slow, does not follow the geographical pattern of silent variation. It opposes European to both African populations, and probably results from selection for adaptation to alcohol in recent temperate populations.

History and Structure of Sub-Saharan Populations ofDrosophila melanogaster

“…Evidence for east-west structure included pairwise F ST values, Mantel test results indicating a significant correlation between genetic and geographic distance within all of sub-Saharan Africa but not within the eastern and western population groups, neighbor-joining population distance trees depicting the separation between eastern and western populations, Structure analysis of sub-Saharan populations showing a correlation between longitude and the cluster membership of populations, and AMOVA analysis indicating that considerably more variation exists between eastern and western population groupings than among populations within those groups. These findings are consistent with previous studies of inversion frequencies (Lemeunier and Aulard 1992;Aulard et al 2002) and studies of molecular variation that had found significant differentiation between one (or two) eastern and one western African population sample (e.g., Bénassi and Veuille 1995;Michalakis and Veuille 1996;Haddrill et al 2005).…”

“…In contrast, studies of silent variation among Adh slow haplotypes (Bénassi and Veuille 1995) and length variation in trinucleotide coding repeats (Michalakis and Veuille 1996) found substantial differentiation between an eastern (Malawi) and a western African (Ivory Coast) population. In both of these studies, the greatest divergence was found between Malawi, on the one hand, and Ivory Coast and the cosmopolitan samples on the other hand.…”

Contrasted Polymorphism Patterns in a Large Sample of Populations From the Evolutionary Genetics Model Drosophila simulans

“…More recent studies based on molecular markers have confirmed that African D. melanogaster populations are genetically differentiated (Bénassi and Veuille 1995;Michalakis and Veuille 1996;Veuille et al 1998;Baudry et al 2004). In D. simulans, Hamblin and Veuille (1999) studied two genes, vermilion (v) and Glucose-6 phosphate dehydrogenase (G6pd), in several populations from the Old and the New World.…”

Environmental Stress, Adaptation and Evolution

“…Invariably the frequency of Adh s is high at the equator and declines with latitude. This clinal behaviour has been found in North America and Australasia (Parkash and Shamina, 1994;Bubli et aI., 1996), Europe and Africa (David et aI., 1989;Benassi and Veuille, 1995;Bubli et aI., 1996) and most recently in Central and South America ( Van 't Land et aI., 1993;Van 't Land et aI., 1995;Van 't Land, 1997). The latter populations, for example, showed high Adh s frequencies, varying from 0.85-0.96 for Panamanian populations (latitudinal range from 7°45'N to 9°19'N) and even as high as 0.99 in Ecuador (latitude 2° 13'S), while Adh s frequencies varied clinally from 0.34-0.07 over a long North-South transect in Chile (latitudinal range from 18°28'S to 41 °30'S).…”