Fig. 2:

Estimated power curves (solid) for each of the three QTL genotypes, QQ (green), Qq (blue) and qq (red), in a comparison with the hypothesized curves (dot) used to 200 simulate individual power curves (under the heritability of 0.4). The consistency between the estimated and hypothesized curves suggests that our model can provide the precise estimation of the genetic control over power curves in flying birds. The differences among the three curves are highly significant (LR = 395, P < 0.001), suggesting that the assumed QTL plays a pivotal role in shaping the power curve in birds. This power curve QTL is further tested for its genetic effects on two ecologically important flight speeds, the minimum power speed (V_mp) and the maximum range speed (V_mr). The three genotype-dependent values for each of these two speeds differ significantly (P < 0.001), implying that the detected QTL also affects the two speeds and, thus, the strategy for bird migration.