The Molecular Clock of Neutral Evolution Can Be Accelerated or Slowed by Asymmetric Spatial Structure
Fig 6
A model of a population divided into upstream and downstream subpopulations.
Each subpopulation is well-mixed. The replacement probability eij equals e↑ if sites i and j are both upstream, e↓ if i and j are both downstream, e→ if i is upstream and j is downstream, and e← if i is downstream and j is upstream. We suppose there is net gene flow downstream, so that e→ > e←. We find that the molecular clock is accelerated, relative to the well-mixed case, if and only if the upstream subpopulation experiences more turnover than the downstream subpopulation: K > u if and only if d↑ > d↓.