MOLECULAR AND CHROMOSOMAL PHYLOGENY IN THE OBSCURA GROUP OF DROSOPHILA INFERRED FROM SEQUENCES OF THE RP49 GENE REGION

A region of approximately 1.6 kb encompassing the ribosomal protein 49 gene (rp49) has been sequenced and compared in nine species of the ob scura group of Drosophila: four species belonging to the obscura subgr oup, three to the pseudoobscura subgroup, and two to the affinis subgr oup. Our data provide strong support that the Nearctic species (pseudo obscura and affinis subgroups) are monophyletic and place D. bifasciat a with the other species of the obscura subgroup. Nucleotide sequence information at the rp49 gene region (located very close to one of the breakpoints of inversion O-3) has also been used to infer the phylogen y of the O chromosome in the subobscura species cluster. Analysis base d both on parsimony-informative sites and on genetic distances confirm s that the O-3 gene arrangement, present in D. guanche (together with inversion g) and in D. madeirensis, is ancestral to gene arrangements O3+4 and O-st present in extant populations of D. subobscura. (C) 1998 Academic Press.