The magnitude of directional selection
([beta]) on life history traits detected in this study (range 0.
The analysis of standardized selection differentials revealed only directional selection
on tibia length favoring females (Fig.
While feeding structures typically are subject to stabilizing selection, favoring optimal cost-effectiveness, structures used in antipredator defense are subject to directional selection
, favoring maximum affordable effect (cf.
Unlike least squares regression, this procedure may only reveal directional selection
, but says nothing regarding nonlinear selection (Price and Boag 1987).
Moreover, this correlated response was not simply due to genetic drift acting alone, because the linear trend suggested that directional selection
was an important factor.
where [Gamma] is the matrix of nonlinear selection coefficients and [Beta] is the vector of directional selection
gradients and the superscript T denotes matrix transposition (eq.
Comparisons of directional selection
coefficient between HL and FP populations planted in their native sites revealed a significant difference for only one trait.
However, the two genes, Tas2r49 and Tas2r3, were associated with bitter taste and were under directional selection
between the QIN and non-QIN populations, showing no signal of directional selection
between MIN and QXL populations.
Predicting microevolutionary responses to directional selection
on heritable variation.
2] is not a lethal selection agent, nor results in strong directional selection
Correct experimental designs to estimate heritability for continuous and threshold traits from a directional selection
experiment are given, as well as appropriate standard errors of the estimates, properly accounting for sampling variance and variance from drift.
Because such traits signal one's overall fitness, they tend to become exaggerated through evolution, in a process called directional selection