Alternatively, Paterson's recognition species concept (Paterson 1985) and Carson's organization theory of speciation (Carson 1985) suggest strong stabilizing selection
on sexual characters within species.
We thus arrive at the surprising result that stabilizing selection
moves the system to a point that is poised to become maximally unstable should it be subjected to decanalizing selection.
Deleterious mutations, apparent stabilizing selection
and the maintenance of quantitative variation.
To illustrate how selection acts to alter the joint distribution of maternal and offspring characters, we start with the common scenario in which the offspring trait is under stabilizing selection
. Early body size in mammals is a classic example of a trait that is influenced by maternal effects and that also experiences stabilizing selection
Natural selection will reduce phenotypic variation in a trait subject to stabilizing selection
either by reducing the genetic variation in the alleles coding for that trait (e.g., removing deleterious mutations) or by reducing the magnitude of the alleles' effects (termed canalization).
Levene's test, comparing absolute deviations from the sample median (Schultz 1983; Manly 1985a,b), was used to test for differences in variation between dominant and subordinate male populations and to detect the potential for stabilizing selection
. An overall difference in variation between dominant and subordinate males, considering the quantities of the three chemical compounds jointly, was analyzed using the generalization of Levene's test suggested by Manly (1985a,b).
The focus on evolutionary change in general, and the cladistic methodology in particular, has unfortunately discouraged the study of adaptation in terms of maintenance by stabilizing selection
. Cladists are adamant in allowing only derived traits as putative adaptations; characters maintained in their ancestral states need no further explanation (e.g., Coddington 1988, 1990; Baum and Larson 1991; Brooks and McLennan 1991).
The strength of stabilizing selection
is inversely related to [s.sub.j].
The sign of the gradient indicates whether the fitness function is concave downward (negative = stabilizing selection
) or concave upward (positive = disruptive selection).
Not only can the local optima change, but the strength of stabilizing selection
around these optima and their relative heights can change, causing transitions between peaks.
These traits appear to be under weak stabilizing selection
, probably due to the pleiotropic effects of alleles on other traits (Nuzhdin et al.
Polygenic variation and stabilizing selection
in a wild population of lesser snow geese (Anser caerulescens caerulescens).