Article,
Inferring the evolutionary histories of the Adh and Adh-dup loci in Drosophila melanogaster from patterns of polymorphism and divergence.
127 (3): 565--582 (1991)
Abstract
The DNA sequences of 11 Drosophila melanogaster lines are compared across three contiguous
regions, the Adh and Adh-dup loci and a noncoding 5’ flanking region of Adh. Ninety-eight of
approximately 4750 sites are segregating in the sample, 36 in the 5’ flanking region, 38 in Adh and
24 in Adh-dup. Several methods are presented to test whether the patterns and levels of polymorphism
are consistent with neutral molecular evolution. The analysis of within- and between-species polymor-
phism indicates that the region is evolving in a nonneutral and complex fashion. A graphical analysis
of the data provides support for a hypothesized balanced polymorphism at or near position 1490, site
of the amino acid replacement difference between Adhfand Adh’. The Adh-dup locus is less polymor-
phic than Adh and all 24 of its polymorphisms occur at low frequency-suggestive of a recent selective
substitution in the Adh-dup region. Adh’ alleles form two distinct evolutionary lineages that differ one
from another at a total of nineteen sites in the Adh and Adh-dup loci. The polymorphisms are in
complete linkage disequilibrium. A recombination experiment failed to find evidence for recombi-
nation suppression between the two allelic classes. Two hypotheses are presented to account for the
widespread distribution of the two divergent lineages in natural populations. Natural selection appears
to have played an important role in governing the overall patterns of nucleotide variation across the
two-gene region.
