nonrandom mating


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as·sort·a·tive mat·ing

selection of a mate with preference for (or aversion to) a particular genotype, that is, nonrandom mating.
Synonym(s): nonrandom mating

nonrandom mating

any mating in a population where crosses between the various types of individuals do not occur in the frequencies that are expected by chance. Two major types of nonrandom mating can be distinguished: between individuals that are related (see INBREEDING), and between individuals with similar phenotypes (see ASSORTATIVE MATING).
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The effects of nonrandom mating, different population sizes, or changes in the magnitude of selection, mutation, or migration can be evaluated independently or in combination with one or more of the other forces.
If, however, homo- or heterozygotes enjoy higher fitness (i.e., selection is acting), then nonrandom mating can also have effects on the rate of change in allele frequencies and can alter both the mean and variance of fitness and other quantitative genetic traits.
Indirect forces, including indirect selection, act on the introduced preference allele largely through its genetic association with the male trait [T.sub.2], which arises by both nonrandom mating and migration.
Crow and Denniston (1988) have derived equations for variance effective size in a population of unequal and variable numbers of male and female individuals under nonrandom mating. One of the equations (33) derived by them, however, considers no distinction between sexes of the offspring and thus it gives correct answers for random mating and Poisson distribution of family size, but not in general (Caballero and Hill 1992a).
Positive assortative mating (including selfing) occurred in three of the seven cases examined; thus, allowance for nonrandom mating was a necessary attribute of the model used to calculate selection.
Even though nonrandom mating was observed for both fathers and sons, no heritable genetic component to male copulatory success was found.
In terms of the intensity of mate choice, there should be unequivocal support for nonrandom mating with respect to some sire character and for female choice as the mechanism producing this nonrandom pattern.
Thus, with nonrandom mating, the apparent fitness of a marker locus will be influenced by selection pressure at other loci, even if overdominance is responsible for variance in fitness.
Nonrandom mating directly creates genetic covariance between preference and preferred trait genes, [B.sub.t1p1], [B.sub.t[prime]1p1], [B.sub.t2p2], and [B.sub.t[prime]2p2].
When the lines selected for increased or decreased activity were tested for nonrandom mating, a 50% excess of homotypic mating was observed (i.e., the percentage of homotypic matings was about 75 instead of the random-mating expectation of 50).
The linkage disequilibrium can arise because of nonrandom mating, with the most discriminating females mating with males carrying the most elaborate characters.
Nonrandom mating in wild radish: variation in pollen donor success and effects of multiple paternity among one- to six-donor pollinations.