Figure 2.
Geographical distance, outlier number and gene flow. (a) The relationship between the number of outliers and geographical distance (both on log10 scale), for geographically separated and geographically adjacent population pairs (filled and unfilled circles, respectively). Both the effects of geographical distance itself, and of geographical arrangement (separated versus adjacent) were statistically significant. The thick arrow labels the point at which zero gene flow between population pairs was inferred (see b and electronic supplementary material, table S2). (b) Estimates of gene flow fall to zero before the maximum separation distance between population pairs examined. The numbers beside each data point refer to the posterior probability of a model with zero gene flow.