In summary, experimental evolution is a powerful approach that will continue to elucidate the rate of evolutionary change, the presence of genetic variation for traits that are under selection, and the role of genetic correlations in evolutionary change. Over generations the lines diverge; after roughly 7–10 generations the differences are apparent and by the 30th generation the differences are extreme. Artificial selection is a breeding process in which a population of organisms is screened for some quantitative trait or traits and those individuals rated highest are used as parents for the next generation. He selectively bred Brassica plants that produced an extra cotyledon and reported an increase in frequency of plants with three and even four cotyledons in subsequent generations. Hill, in Reference Module in Life Sciences, 2017. Abraham B. Korol, in Encyclopedia of Biodiversity (Second Edition), 2013. While such variation has been clearly demonstrable in virtually every behavioral selection attempted, from maze learning in rats to gravity response in Drosophila, there has been no way to identify any of the relevant genes. Each symbol represents a line of flies selected for high or low speed. Sci. Artificial selection is the basic method of genetic improvement programs for crop plants or livestock (see Selective Breeding). 1), 6622–6629. Mongold et al. Consequently, only when populations decline in abundance does adaptation to such extreme thermal conditions proceed, a clear example of the intimate connection between demographic and genetic change. That is, selection had eliminated the vast majority of one foraging allele from each population. <>
Perhaps the broadest range of artificially selected behavior is seen in domestic dogs, which display a wide variety of behavioral attributes. The conditions necessary to impose selection on the foraging locus are easier to imagine and implement, and the outcome leads to the conclusion that being genetically rover is advantageous under crowded conditions, whereas being genetically sitter is advantageous under conditions of low density. Adapted from Mackay T.F., et al., 2005 Proc Natl Acad Sci U S A May 3 102 Suppl 1:6622–9, Rosenberg's Molecular and Genetic Basis of Neurological and Psychiatric Disease (Fifth Edition), Encyclopedia of Biodiversity (Second Edition), International Encyclopedia of the Social & Behavioral Sciences, Selection for Changed Recombination, Genetic Modifiers of Recombination, Intraspecific Variation for the Rate of Recombination. Natl. Most domestic livestock (such as chickens, horses, cattle, sheep, goats, and swine) reflect the results of artificial selection for manageability in confinement, ease of training, and docility (see Figure 3.9). Perhaps the broadest range of artificially selected behavior is seen in domestic dogs, which display a wide variety of behavioral attributes. Artificial selection is a man-made selection process of the desired character, and it is mainly used in enhanced livestock and crops. Artificial selection, in scientific laboratories and in animal husbandry, has dramatic effects on behavior. Humans engage in artificial selection to create specific plants and animals. An alternative approach is to expose a population to an environment (e.g., higher temperatures) in which genetic variation in fitness is expressed, such that natural selection proceeds (Bennett et al., 1992). Michael D. Breed, Janice Moore, in Animal Behavior, 2012. If there is additive genetic variance for the selected trait, it will respond to the selection, that is, the trait will evolve. From: Brenner's Encyclopedia of Genetics (Second Edition), 2013, JK Conner, in Encyclopedia of Evolutionary Biology, 2016. These explanations of repair functions were called “physiological” (Maynard Smith, 1978). 2 0 obj
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For example, artificial selection studies have shown that it is possible that shifts in flowering time in herbaceous plant species that have been observed in nature (Parmesan and Yohe, 2003) may be due, in part, to evolutionary change (Burgess et al., 2007). Understanding the forces maintaining sex and recombination is considered one of the most challenging problems in evolutionary theory (Michod and Levin, 1988). Now there are a variety of rat and mouse lines selectively bred to differ in various responses to ethanol, including drinking preference, tolerance and withdrawal severity.42 One of the features of selective breeding is that selecting for one trait leads to the development of correlated pleiotropic differences in many other traits. Shared genetic control and molecular mechanisms of DNA recombination and DNA repair across life (see Meiotic Mutants as an Analytical Tool in Recombination Studies: Overlapping of DNA Repair, Recombination, and Segregation Systems and Molecular Mechanisms of Recombination) indicate their common evolutionary origin and functional overlap in extant organisms. From eqn [1] we can see that if the strength of selection (S) is experimentally determined and the response to selection (R) is observed, we can estimate the realized heritability (h2) of the trait of interest. %PDF-1.5
Artificial selection experiments suggest that almost every population has enough stored genetic variability to ensure response to direct selection for changed recombination frequency (see Selection for Changed Recombination, Genetic Modifiers of Recombination, and Intraspecific Variation for the Rate of Recombination). <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>>
Only their approximate number and putative interactions could be estimated from statistical analyses of selected lines and of F1, F2, and backcross progeny. endobj
The selected individuals are interbred with the expectation that, if the trait is heritable, its phenotypic mean will differ in the offspring of the subsequent generation.