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Stabilizing selection is the most common form of nonlinear selection (non-directional) in humans. [13] There are few examples of genes with direct evidence of stabilizing selection in humans. However, most quantitative traits (height, birthweight, schizophrenia) are thought to be under stabilizing selection, due to their polygenicity and the ...
Group A is the original population and Group B is the population after selection. Top (Graph 1) represents directional selection with one extreme favored. Middle (Graph 2) represents stabilizing selection with the moderate trait favored. Bottom (Graph 3) represents disruptive selection with both extremes being favored.
In evolutionary biology, disruptive selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into two distinct groups.
Selection can be divided into three classes, on the basis of its effect on allele frequencies: directional, stabilizing, and disruptive selection. [103] Directional selection occurs when an allele has a greater fitness than others, so that it increases in frequency, gaining an increasing share in the population.
In a study of the fresh-water Eurasian perch, a change in fitness was reported with a change in their density. An estimate of the selection gradient by linear and quadratic regression indicated a shift of the selection regime between stabilizing and directional selection at low density to disruptive selection at higher density. [11]
The incidental purging of non-deleterious alleles due to such spatial proximity to deleterious alleles is called background selection. [4] This effect increases with lower mutation rate but decreases with higher recombination rate. [5] Purifying selection can be split into purging by non-random mating (assortative mating) and purging by genetic ...
[3]: 357 In general, two types of experiments have been conducted: using artificial selection to mimic natural selection that eliminates the hybrids (often called "destroy-the-hybrids"), and using disruptive selection to select for a trait (regardless of its function in sexual reproduction).
Mathematical models, laboratory studies, and observational evidence supports the existence of parapatric speciation's occurrence in nature. The qualities of parapatry imply a partial extrinsic barrier during divergence; [2] thus leading to a difficulty in determining whether this mode of speciation actually occurred, or if an alternative mode (notably, allopatric speciation) can explain the data.