formerly discussed, disruptive selection
may generate new taxa.
So, could disruptive selection
have contributed to today's rainbow of birds?
First, the populations may be species that arose very recently and differentiated under strong disruptive selection
. Second, the populations could be host races.
in this species should favor a correlation between male morphology and male behavior, so that all guarding males have long horns, and all sneaking males are hornless.
To this end, the work reported in this study considers the genetical variation for host utilization of a herbivore population which had been subject to very limited, if any, disruptive selection
with respect to plant-specific traits in the current generation, and considers the nature of this genetic variation after recombination.
saxatilis split because of disruptive selection
in two conspecific morphs, one upper-shore and one lower-shore, that still maintain an important gene flux between them (Johannesson et al.
Compared to parametric regression, the cubic spline technique is better able to identify dips and modes that might indicate local stabilizing or disruptive selection
in an otherwise directional selection surface.
Conversely, if the mean drifts sufficiently close to the saddle point, past the transition between stabilizing and disruptive selection
, then increases in variance resulting from disruptive selection
can change the mean fitness function enough to move the saddle point past the mean.
where [Alpha] = 2N[[Sigma].sup.2] is again a measure of the strength of selection and B = 1/c is a parameter reflecting the relative contributions of balancing and disruptive selection
. For the TIM model, B = 1, and there is no balancing selection.
Shape.--To determine whether characters were under stabilizing or disruptive selection
, rather than directional selection, we tested the regressions for second-order effects by entering the square of each standardized character into the regression models.
They applied disruptive selection
to bristle number at two levels: moderate, in which the upper and lower 25% of individuals were selected for breeding, and high, in which the upper and lower 1% of individuals were selected.
The general patterns of stabilizing and disruptive selection
are summarized in table 2.