MITOCHONDRIAL GENE DIVERGENCE OF COLOMBIAN DROSOPHILA-PSEUDOOBSCURA

Isolated populations of Drosophila pseudoobscura, separated from North American populations by about 2,400 km, were found in Colombia in 196 0. We compared for sequences of the small ribosomal RNA (srRNA) gene o n the mitochondria between North American and Colombian D. pseudoobscu ra in order to clarify the age of the Colombian isolates. The North Am erican populations were not genetically different from each other but were genetically different from the Colombian populations. The Mexican strains represent the area from which the Colombian founders might ha ve come. The estimated net nucleotide divergence between Mexican and C olombian D. pseudoobscura indicates that the Colombian population is n ot an ancient lineage. Phylogenies using both distance and parsimony m ethodologies reinforced this conclusion. The Colombian samples group t ogether with both methods but, according to the bootstrap analysis, no t significantly. It appears that the populations have not been separat ed long enough for their DNA sequences to show much divergence.