Sympatric Speciation in Threespine Stickleback: Why Not?

Figure 2

Lake populations exhibit a tendency towards disruptive selection (positive quadratic selection coefficients). Box plots represent the mean (thick vertical lines), 50th quartiles (boxes), and range (whiskers) of quadratic selection gradients for gill raker length and gill raker number from 14 populations, represented as individual dots [24]. P values are provided for t-tests of whether the mean quadratic selection gradient is significantly different from zero. The values are modified from [24], who reported the quadratic coefficients γ whereas disruptive selection should be measured as 2γ as shown here.