In This Article Expand or collapse the "in this article" section Reinforcement

  • Introduction
  • General Overviews
  • Journals
  • Sources of Ecological Selection
  • Alternative Explanations

Evolutionary Biology Reinforcement
Henry Arenas-Castro, Beth Brittain, Daniel R. Matute, Daniel Ortiz-Barrientos
  • LAST REVIEWED: 26 June 2019
  • LAST MODIFIED: 26 June 2019
  • DOI: 10.1093/obo/9780199941728-0120


Reinforcement, or the strengthening of reproductive isolation in response to hybridization costs, is a case in which natural selection directly contributes to the origin of new species. From its conception, reinforcement has enjoyed alternate periods of enthusiasm and rejection, in which powerful verbal arguments identified obstacles that were subsequently solved by novel theory. Empirical data has provided some of the strongest arguments for the plausibility of reinforcement and for its frequency in nature, indicating that it is likely to be a common aspect of species divergence and the completion of speciation.

General Overviews

General overviews on reinforcement lagged in the speciation literature for more than four decades after the formal introduction of the idea by Dobzhansky 1940. Noor 1999 and Servedio and Noor 2003 are comprehensive overviews, expanded by Ortiz-Barrientos, et al. 2009, that followed many theoretical and empirical studies initially stimulated by Butlin 1987. These general overviews provided the framework for most of the subsequent research on reinforcement. The Pfennig and Pfennig 2009 and Lenormand 2012 reviews offer alternative frameworks of this process. The Hopkins 2013 review is the most recently updated overview on reinforcement, with a focus on plants.

  • Butlin, R. K. 1987. Speciation by reinforcement. Trends in Ecology & Evolution 2:8–13.

    DOI: 10.1016/0169-5347(87)90193-5

    Butlin describes the history of the idea of reinforcement as well as theoretical considerations that raise doubts about its occurrence in nature. Although he does not deny the possibility of reinforcement, he gives it little support as an important mechanism in speciation.

  • Dobzhansky, T. 1940. Speciation as a stage in evolutionary divergence. American Naturalist 74:312–321.

    DOI: 10.1086/280899

    In this seminal paper, Dobzhansky stresses the importance of developing isolating mechanisms that prevent interbreeding for the formation and maintenance of species as distinct adaptive complexes. He argues that when hybridization jeopardizes the integrity of these complexes, selection should favor genetic factors that prevent interbreeding.

  • Hopkins, R. 2013. Reinforcement in plants. New Phytologist 197:1095–1103.

    DOI: 10.1111/nph.12119

    Hopkins provides a general overview of the use of the term reinforcement and delineates four criteria to determine whether reinforcement causes divergence. She also offers a detailed account of reinforcement studies in plants.

  • Lenormand, T. 2012. From local adaptation to speciation: Specialization and reinforcement. International Journal of Ecology 2012:1–11.

    DOI: 10.1155/2012/508458

    Lenormand argues for the integration of local adaptation into the core of speciation theory by proposing that selection against locally maladapted genotypes is a major force driving reinforcement of reproductive isolation. Reinforcement is treated as a positive feedback loop between locally adapted alleles and those causing increase premating isolation.

  • Noor, M. A. F. 1999. Reinforcement and other consequences of sympatry. Heredity 83:503–508.

    DOI: 10.1038/sj.hdy.6886320

    Noor reviews the theoretical and empirical data that challenge and support the role of reinforcement in speciation. He also presents a set of alternative mechanisms that can produce the same pattern of reinforcement: greater mating discrimination in sympatry than in allopatry.

  • Ortiz-Barrientos, D., A. Grealy, and P. 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

    Here, authors broaden the perspective of the research agenda of reinforcement to address new and long-standing questions on the genetic and ecological basis of speciation.

  • Pfennig, K. S., and D. W. Pfennig. 2009. Character displacement: Ecological and reproductive responses to a common evolutionary problem. Quarterly Review of Biology 84:253–276.

    DOI: 10.1086/605079

    Pfennig and Pfennig place reinforcement in the ecological and evolutionary framework of character displacement and explore its interaction with other forms of character displacement.

  • Servedio, M. R., and M. 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

    Servedio and Noor review the models and evidence for reinforcement and assess whether data match theoretical predictions. They propose a novel research program to fill major gaps in our understanding of reinforcement given the strong evidence that reinforcement occurs in nature under many conditions.

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