Concept: Adaptive diversification. Also: allopatric diversification; sympatric diversification; frequency-dependent selection.
Source: An (original research) article published in PLoS Biology (February 19, 2013)
- Background: A dichotomy of diversification follows depending on whether the ancestral populations were geographically isolated from each other (allopatric diversification) or not (sympatric diversification).
- History: Same authors show that a single strain grown in the presence of both glucose and acetate diversify into coexisting stable populations that (relatively) specialize in using either glucose/acetate.
- Experiment setup: Same as before, but now conduct whole-genome sequencing from three replicate diverged populations. Sequence not only at end-point, but also use frozen samples collected in intermediate generations.
- Results: All three replicates had similar evolutionary trajectories. First to develop are rare glucose-specialization mutations (100 generations) that eventually dominate (300 gen’s); after which acetate-specialization mutations gain frequency, until eventually, both types co-exist at intermediate levels until the end of the experiment (1045 gen’s). This is consistent with frequency-dependent selection in which the frequency of one strain causes (and so correlates with) the selective pressure on another strain. Here dominance of glucose metabolizers would create a relative excess of acetate enabling an advantage for acetate metabolizers.
