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

Abstract

A 793-nucleotide fragment from the D. subobscuraOdh 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 O5 inversion, the same association found in North America. Two different haplotypes were detected in association with the O3+4+7̄ 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 (O3+4+7̄/O3+4+7̄) between the various genetic elements (for e.g. the lethal genes and Odh haplotypes) located inside the O7 inversion. The infrequent O7 inversion was observed in the Puerto Montt population presenting one of the haplotypes found only in the O3+4+7̄ chromosomal arrangement. Thus, we confirmed the hypothesis that the origin of this inversion is based on a recombination event in a heterokaryotype O3+4+7̄/Ost. Although one haplotype has been associated with the O3+4+2̄ arrangement, the latter also presents another haplotype shared with both O3+4+8 and Ost. Finally, similar nucleotide diversity values were observed in both Chilean populations.