MOLECULAR EVOLUTION OF THE AMY MULTIGENES IN THE SUBGENUS SOPHOPHORA OF DROSOPHILA

Molecular evolution of the Amy multigenes in Drosophila was investigat ed using PCR amplification. Twenty-five partial Amy sequences from 13 species belonging mainly to the subgenus Sophophora were determined, a nd a molecular phylogeny of the Amy genes in Drosophila was constructe d, together with published Amy sequences. Clusterings of species are m ostly consistent with the traditional classification and that inferred from other genes. From sequence divergence between PCR products, seve ral species, including D, elegans and D, fuyamai, were suggested to ha ve multiple copies of the Amy genes. The loss of an intron took place at least three times after the Sophophora radiation. In order to inves tigate the mechanism of sequence evolution, the numbers of amino acid replacement and synonymous substitutions in five lineages were estimat ed. The heterogeneity in the relative numbers of synonymous and replac ement substitutions among the lineages was found. Possible roles of se lection in the sequence evolution of the Amy gene are discussed.