adaptive landscape

Barton NH, Briggs DEG, Eisen JA, Goldstein DB & Patel NH 2007 Evolution. Cold Spring Harbor Laboratory Press. ISBN:9780879696849

• selection tends to increase mean fitness W, so that populations climb toward peaks in the adaptive landscape
• in a balance between random drift and selection, a collection of populations will tend to cluster around adaptive peaks
• with a probability distribution proportional to W^2N_e
• Wright's formula shows how allele frequencies cluster around adaptive peaks when populations have reached a steady state between the different evolutionary processes
• we can also ask about the rates of shifts between adaptive peaks
• the rate of shifts between peaks depends primarily on the chance of drifting to the saddle point relative to the chance of being at the peak
• this ratio is proportional to W_saddle^2N_e / W_peak^2N_e
• (pp. 494-496)