Molecular variation in the Odh gene in Chilean natural populations of Drosophila subobscura

A 793-nucleotide fragment from the D. subobscura Odh gene was sequenced in 46 lethal chromosomal lines from two South American colonizing populations (18 from Santiago de Chile and 28 from Puerto Montt). Only eight different haplotypes were found and, with just one exception, all had previously been detected in North American samples. The exception probably corresponds to a genetic exchange between two American haplotypes. Our results confirm the loss in genetic variability due to the recent founder event, and the high resemblance between the two colonized hemispheres. One haplotype is entirely associated with the O-5 inversion, the same association found in North America. Two different haplotypes were detected in association with the O(3+4) under bar+(7) under bar chromosomal arrangement. The chromosomal lines featuring this arrangement carried different lethal genes, although there is no association between the latter genes and the two Odh haplotypes. There may be free exchange in the homokaryotypes (O(3+4) under bar+(7) under bar /O (3+4) under bar+(7) under bar) between the various genetic elements (for e. g. the lethal genes and Odh haplotypes) located inside the O-7 inversion. The infrequent O7 inversion was observed in the Puerto Montt population presenting one of the haplotypes found only in the O(3+4) under bar+(7) under bar chromosomal arrangement. Thus, we confirmed the hypothesis that the origin of this inversion is based on a recombination event in a heterokaryotype O(3+4) under bar+(7) under bar/O-st. Although one haplotype has been associated with the O(3+4) under bar+(7) under bar arrangement, the latter also presents another haplotype shared with both O(3+4) under bar+(7) under bar and O-st. Finally, similar nucleotide diversity values were observed in both Chilean populations.