Hybrid Zone Recognition
All hybrids produced may be equality low-fitness,  conferring a broad disadvantage. In other cases, selection may favor multiple and varying phenotypes  such as in the case of a mosaic hybrid zone. In cases where an allele is indirectly selected, its frequency increases due to a different linked allele experiencing selection linkage disequilibrium.
The condition of the hybrids under selection can play a role in post-zygotic isolation, as hybrid inviability a hybrid unable to mature into a fit adult and sterility the inability to produce offspring entirely prohibit gene flow between populations. Some initial divergence in mate preference must be present for reinforcement to occur. The evidence for reinforcement comes from observations in nature, comparative studies, and laboratory experiments.
Original Research ARTICLE
Reinforcement can be shown to be occurring or to have occurred in the past by measuring the strength of prezygotic isolation in a sympatric population in comparison to an allopatric population of the same species. Reinforcement's ubiquity is unknown,  but the patterns of reproductive character displacement are found across numerous taxa and is considered to be a common occurrence in nature. Assortive mating is expected to increase among sympatric populations experiencing reinforcement. Laboratory studies that explicitly test for reinforcement are limited,  : with many of the experiments having been conducted on Drosophila fruit flies.
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. Rice and Ellen E. Hostert contend that they do not truly model reinforcement, as gene flow is completely restricted between two populations. Various alternative explanations for the patterns observed in nature have been proposed.
Ecology can also play a role in the observed patterns—called ecological character displacement. Natural selection may drive the reduction of an overlap of niches between species instead of acting to reduce hybridization  : Though one experiment in stickleback fish that explicitly tested this hypotheses found no evidence. Species interactions can also result in reproductive character displacement in both mate preference or mating signal. Hoskin and Megan Higgie give five criteria for reinforcement to be distinguished between ecological and ethological influences:. Results will be most informative in a well-resolved biogeographic setting where the relationship and history among populations is known.
It is possible that the pattern of enhanced isolation could simply be a temporary outcome of secondary contact where two allopatric species already have a varying range of prezygotic isolation: with some exhibiting more than others. It is possible that the process of sympatric speciation itself may result in the observed patterns of reinforcement. In a runaway process not unlike Fisherian runaway selection , selection against the low-fitness hybrids favors assortive mating, increasing mate discrimination rapidly.
A number of objections were put forth, mainly during the s, arguing that reinforcement is implausible. Concerns about hybrid fitness playing a role in reinforcement has led to objections based on the relationship between selection and recombination. Somehow, the populations must be maintained. In addition, specific alleles that have the selective advantage within the overlapped populations are only useful within that population.
Do changes in gene expression contribute to sexual isolation and reinforcement in the house mouse?
Recent studies suggest reinforcement can occur under a wider range of conditions than previously thought    : — and that the effect of gene flow can be overcome by selection. In conjunction with the fusion hypothesis, reinforcement can be thought of as a race against both fusion and extinction. From Wikipedia, the free encyclopedia. Not to be confused with Secondary contact. Darwin's finches by John Gould. Key topics. Introduction to evolution Evidence of evolution Common descent Evidence of common descent. Processes and outcomes.
Natural history. History of evolutionary theory. Fields and applications. Applications of evolution Biosocial criminology Ecological genetics Evolutionary aesthetics Evolutionary anthropology Evolutionary computation Evolutionary ecology Evolutionary economics Evolutionary epistemology Evolutionary ethics Evolutionary game theory Evolutionary linguistics Evolutionary medicine Evolutionary neuroscience Evolutionary physiology Evolutionary psychology Experimental evolution Phylogenetics Paleontology Selective breeding Speciation experiments Sociobiology Systematics Universal Darwinism.
Social implications. Evolution as fact and theory Social effects Creation—evolution controversy Objections to evolution Level of support. Main article: Evidence for speciation by reinforcement.
Genome-wide patterns of gene flow across a house mouse hybrid zone
See also: Laboratory experiments of speciation. Hood, Scott P. Egan, and Jeffrey L. Marshall, Michael L. Arnold, and Daniel J. Coyne ; H. Allen Orr , Speciation , Sinauer Associates, pp. Servedio; Mohamed A. Noor , "Reinforcement and other consequences of sympatry", Heredity , 83 5 : —, doi : Butlin and Carole M. Littlejohn Reproductive isolation: A critical review. Atchley and D. Frank , "Mating call and stage of speciation in the Microhyla olivacea-M. Genetics and the Origin of Species. Columbia University Press. In Otte, D. Speciation and its Consequences.
Sinauer Associates. In Harrison, R. Hybrid Zones and the Evolutionary Process. Oxford University Press. Hvala and Troy E. Wood Speciation: Introduction. Hoskin and Megan Higgie , "Speciation via species interactions: the divergence of mating traits within species", Ecology Letters , 13 4 : —, doi : Liou and Trevor D. Price , "Speciation by reinforcement of premating isolation", Evolution , 48 5 : —, doi : Servedio and Mark Kirkpatrick , "The effects of gene flow on reinforcement", Evolution , 51 6 : —, doi : Barton; Jerry A. Servedio , "Reinforcement and the genetics of nonrandom mating", Evolution , 54 1 : 21—29, doi : Cain, Viggo Andreasen, and Daniel J.
Howard , "Reinforcing selection is effective under a relatively broad set of conditions in a mosaic hybrid zone", Evolution , 53 5 : —, doi : As their battle for her draws her ever deeper into their world, Macy is forced on a journey of self-discovery that ultimately leads her to decide what in life is worth fighting for. Get A Copy. Kindle Edition , pages. More Details Other Editions 2.
Identification of a hybrid myocardial zone in the mammalian heart after birth
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I had a hard time believing that such an intelligent scientist would have such an easy time accepting the inner world of hybrids. Was she scorned by a previous lover? Is she just a bit on the prudish side? Their romance kind of blossomed without any notice…it just happened. The story itself is a quick look into the fringe world of science and it will definitely keep you on your toes until the end. View 1 comment. Jenny Koch rated it it was amazing May 04, Hemera rated it it was amazing Aug 09, Hildegard rated it really liked it Oct 23, Ashley Boone rated it it was amazing Jul 16, Clever Girl rated it really liked it Nov 29, Beiza added it Dec 20, Barbi Davis marked it as to-read Jun 12, Stephen Robertson marked it as to-read May 02, BookishDreamer marked it as to-read May 06, Ida marked it as to-read May 11, Toni marked it as to-read Oct 13, Amelia Jamison marked it as to-read Nov 07, Stacy Ittersagen marked it as to-read Nov 29, Jonathan Mcdaniel is currently reading it Jan 14, Phil marked it as to-read Feb 02,