Reinforcement (speciation)

Reinforcement assists speciation by selecting against hybrids upon the secondary contact of two separated populations of a species.

Reinforcement is a process of speciation where natural selection increases the reproductive isolation (further divided to pre-zygotic isolation and post-zygotic isolation) between two populations of species. This occurs as a result of selection acting against the production of hybrid individuals of low fitness. The idea was originally developed by Alfred Russel Wallace and is sometimes referred to as the Wallace effect. The modern concept of reinforcement originates from Theodosius Dobzhansky. He envisioned a species separated allopatrically, where during secondary contact the two populations mate, producing hybrids with lower fitness. Natural selection results from the hybrid's inability to produce viable offspring; thus members of one species who do not mate with members of the other have greater reproductive success. This favors the evolution of greater prezygotic isolation (differences in behavior or biology that inhibit formation of hybrid zygotes). Reinforcement is one of the few cases in which selection can favor an increase in prezygotic isolation, influencing the process of speciation directly.[1] This aspect has been particularly appealing among evolutionary biologists.[2]

The support for reinforcement has fluctuated since its inception, and terminological confusion and differences in usage over history have led to multiple meanings and complications. Various objections have been raised by evolutionary biologists as to the plausibility of its occurrence. Since the 1990s, data from theory, experiments, and nature have overcome many of the past objections, rendering reinforcement widely accepted,[3]: 354  though its prevalence in nature remains unknown.[4][5]

Numerous models have been developed to understand its operation in nature, most relying on several facets: genetics, population structures, influences of selection, and mating behaviors. Empirical support for reinforcement exists, both in the laboratory and in nature. Documented examples are found in a wide range of organisms: both vertebrates and invertebrates, fungi, and plants. The secondary contact of originally separated incipient species (the initial stage of speciation) is increasing due to human activities such as the introduction of invasive species or the modification of natural habitats.[6] This has implications for measures of biodiversity and may become more relevant in the future.[6]

  1. ^ Hannes Schuler, Glen R. Hood, Scott P. Egan, and Jeffrey L. Feder (2016), Meyers, Robert A (ed.), "Modes and Mechanisms of Speciation", Reviews in Cell Biology and Molecular Medicine, 2 (3): 60–93, doi:10.1002/3527600906, ISBN 9783527600908{{citation}}: CS1 maint: multiple names: authors list (link)
  2. ^ Jeremy L. Marshall, Michael L. Arnold, and Daniel J. Howard (2002), "Reinforcement: the road not taken", Trends in Ecology & Evolution, 17 (12): 558–563, doi:10.1016/S0169-5347(02)02636-8{{citation}}: CS1 maint: multiple names: authors list (link)
  3. ^ Jerry A. Coyne; H. Allen Orr (2004), Speciation, Sinauer Associates, pp. 1–545, ISBN 978-0-87893-091-3
  4. ^ Maria R. Servedio; Mohamed A. F. Noor (2003), "The Role of Reinforcement in Speciation: Theory and Data", Annual Review of Ecology, Evolution, and Systematics, 34: 339–364, doi:10.1146/annurev.ecolsys.34.011802.132412
  5. ^ Daniel Ortíz-Barrientos, Alicia Grealy, and Patrik Nosil (2009), "The Genetics and Ecology of Reinforcement: Implications for the Evolution of Prezygotic Isolation in Sympatry and Beyond", Annals of the New York Academy of Sciences, 1168: 156–182, doi:10.1111/j.1749-6632.2009.04919.x, PMID 19566707, S2CID 4598270{{citation}}: CS1 maint: multiple names: authors list (link)
  6. ^ a b Maria R. Servedio (2004), "The What and Why of Research on Reinforcement", PLOS Biology, 2 (12): 2032–2035, doi:10.1371/journal.pbio.0020420, PMC 535571, PMID 15597115

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