Résumé
Anopheles melas is a brackish water-breeding member of the An. gambiae
complex that is distributed along the coast of West Africa and is a major
malaria vector within its range. Because little is known about the
population structure of this species, we analyzed 15 microsatellite
markers and 1,161 bp of mtDNA in 11 An. melas populations collected
throughout its range. Compared to its sibling species An. gambiae, An.
melas populations have a high level of genetic differentiation between
them, representing its patchy distribution due to its fragmented larval
habitat which is associated with mangroves and salt marsh grass.
Populations clustered into three distinct groups representing Western
Africa, Southern Africa, and Bioko Island populations that appear to be
mostly isolated. Fixed differences in the mtDNA are present between all
three clusters, and a Bayesian clustering analysis of the microsatellite
data found no evidence for migration from mainland to Bioko Island
populations, and little migration was evident between the Southern to the
Western cluster. Surprisingly, mtDNA divergence between the three An.
melas clusters is on par with levels of divergence between other species
of the An. gambiae complex, and no support for monophyly was observed in a
maximum likelihood phylogenetic analysis. Finally, an Approximate Bayesian
Analysis of microsatellite data indicates that Bioko Island An. melas
populations were connected to the mainland populations in the past, but
became isolated, presumably when sea levels rose after the last glaciation
period (≥10,000-11,000 years ago). This study has exposed species level
genetic divergence within An. melas, and also has implications for control
of this malaria vector.