Defining and measuring gene flow

We describe developments of regression-based methods for estimating the rel ationship between gene flow and distance using allelic variation at marker loci. These new methods allow the correct testing of the difference between regression slopes, and the assignment of confidence intervals to estimates from the regression equation, when the regression is between matrices of p airwise data, rather than between independent values. We show that there ar e significant differences in gene flow estimates from RFLPs and isozymes in sea beet. Estimates of the distance at which populations exchange one migr ant per generation are lower for wild cabbage than for sea beet.