patterns of variation among pops:

Figures and Images:

Range of Ponderosa Pine. The map below shows the eastern and western varieties of ponderosa pine, separated by the Great Basin in the south and the Norhtern Rockies to the north. The two varieties have only recently come into secondary contact in a transition zone, just east of the continental divide in west central Montana. Through this transition zone there has been very little gene flow. There is a very steep cline in mtDNA haplotype frequency, and a less steep cline of cpDNA haplotype frequency. Sampling locations are shown on the map, and 95% confidence limits for the frequency of the western haplotype are shown.

Coalescent Simulations : Imagine 1000 independent loci in a population with effective size (Ne) of 1000. For some of those loci, all of the alleles in the population will trace to a very recent common ancestor, while others will trace to a much more distant common ancestor. The histogram below shows this variability. The 2.5th and 97.5th percentiles are shown by the arrows. Basically, for the exact same population, different neutral loci can have very different evolutionary histories.

This translates into a wide range of possible population patterns for neutral loci. For the case of Ponderosa pine, we have a pretty good idea that there are two varieties that have been completely separate for several thousand generations. The figure below shows the distribution of Fst that you would expect for two populations of Ne = 10,000, separated for 5000 generations. Results for three different mutation rates are shown, and the distribution of the observed Fst of allozymes is illustrated by the triangles above the graph.

Fst and Qst: This is a review John McKay and I did a few years ago, comparing the pattern of divergence for molecular genetic markers (Fst on the X-axis) with the corresponding pattern of divergence for quantitative traits (Qst). Each point represents a species (or a study), with the mean Qst given by the black dot, and the range of Qst among different traits in that species given by the two white dots and the dotted line. The diagonal line is the prediction for Fst = Qst. Note that these are shown on a logarithmic scale.

A possible mechanism for divergence with high gene flow. The divergence among populations that you see in a quantitative trait is affected not just by how different the allele frequencies are at the loci that underly that trait, but ALSO by the correlations (covariances) among the allele frequencies at the different loci. In the top panel, the two loci change frequency in opposite directions as you move from population 1 to population 5. This means there is a negative correlation between the allele frequencies. The changes at the two loci cancel out, and there is no change in teh trait. In the lower panel, the allele frequencies change in parallel (a positive correlation), so the trait is actually more diverged among populations than its underlying loci.

Genetic Markers: AFLP differences between ecotypes segregate among the F6 recombinants. Left panel shows fixed differences between Mesic and Xeric genotypes for several loci. Right panel shows alleles for these loci segregating in the F6 - two mesic and two xeric parents are shown on the far right.