Phylogenies and the forces of evolution

Abstract

The construction of phylogenetic trees from gene frequency data assumes that a history of binary fissioning of populations has been the major cause of genetic variation. However, in many areas of the world human populations have been relatively stable with local gene flow. This population history is closer to an isolation by distance model. It was modelled by a simulation of gene frequency changes in a linear sequence of 50 stable populations with gene flow among neighboring populations. Phylogenetic trees were constructed from the gene frequencies after the simulation was run for 500 generations. Using only a few loci there is little correlation between genetic and geographic distance, but with 40 or more loci, there was a perfect correlation with geographic distance. A different population model can thus result in a phylogenetic tree comparable to those assumed to be produced by binary fission.