Molecular evolution of P transposable elements in the genus Drosophila. III. The melanogaster species group |
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Authors: | Clark, JB Kim, PC Kidwell, MG |
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Affiliation: | Department of Ecology and Evolutionary Biology, University of Arizona, Tucson. |
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Abstract: | Phylogenetic relationships were determined for 76 partial P-elementsequences from 14 species of the melanogaster species group within theDrosophila subgenus Sophophora. These results are examined in the contextof the phylogeny of the species from which the sequences were isolated.Sequences from the P-element family fall into distinct subfamilies, orclades, which are often characteristic for particular species subgroups.When examined locally among closely related species, the evolution of Pelements is characterized by vertical transmission, whereby the P-elementphylogeny traces the species phylogeny. On a broader scale, however, theP-element phylogeny is not congruent with the species phylogeny. Onefeature of P-element evolution in the melanogaster group is the presence ofmore than one P-element subfamily, differing by as much as 36%, in thegenomes of some species. Thus, P elements from several individual speciesare not monophyletic, and a likely explanation for the incongruence betweenP-element and species phylogenies is provided by the comparison ofparalogous sequences. In certain instances, horizontal transfer seems to bea valid alternative explanation for lack of congruence between species andP-element phylogenies. The canonical P-element subfamily, which representsthe active, autonomous transposable element, is restricted to D.melanogaster. Thus, its origin clearly lies outside of the melanogasterspecies group, consistent with the earlier conclusion of recent horizontaltransfer. |
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