Negative selection (artificial selection)

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In artificial selection, negative selection is where negative, rather than positive, traits of a species are selected for evolutionary continuance. It is generally not desirable, but may be caused by man-made conditions such as bad management, such as when humans eat the best plants or animals they have, leading to worse and worse stock; it occurred frequently, for example, in primitive beekeeping.^{[citation needed]} Another, more modern, example are regulations on fish and game, where fish below a certain size had to be released, and deer below a certain size could not be hunted, leading to undersized deer and fish populations.^{[citation needed]} Some, such as proponents of Social Darwinism and eugenics argue that medicine and other technological, societal, and cultural practices cause negative selection in humans, also known as dysgenics. According to them, man, as a species, manifests more and more negative traits as a result of this.

In the case of microbiology and molecular biology, negative selection is used to screen for microorganisms that fail to possess a certain phenotype. An example of this is through replica plating.

[edit] Examples

The shellfishes Concholepas concholepas (Chilean abalone) and Loxechinus albus (Chilean sea urchin) have been exposed to over-extraction during a long time. Populations have shrunk and a recent study shows that extraction is making an artificial selection to eliminate faster-growing individuals.^[1] The same study also showed that populations in Chile are relatively homogeneous with low genetic variability.