Genome-wide analysis of a long-term evolution experiment with Drosophila
For decades, most researchers have provided some general insights into the nature of adaptation in asexually reproducing populations with small genome, such as bacteria and yeast. They assumed that sexual species evolve the same way these populations do, i.e. their adaptation is driven by the so-called selective sweeps or newly arising beneficial genetic mutation quickly becomes “fixated” on a particular portion of DNA, with the genome-wide haplotype associated with it. When we relate to obligate sexually reproducing systems, this is much more complicated by the fact that selection can act on standing variation, that means that weak selection can act on many pre-existing genetic variants involved in fitness traits. The idea is that short-term evolution have occurred through a so-called “soft sweep” model, which contrasts the hypothesis of the “hard sweep”, where strong selective sweep originates from a single mutation, while all its linked neutral variants are eliminated. Burke et al. compared outbred, sexually reproducing, replicated populations of D. melanogaster selected for accelerated development and their matched control populations on a genome-wide basis, and this is the first time that such a study of a sexually reproducing species has been done. As shown in figure 1, they used the Illumina …
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