Ring Species and Speciation


A ring species is a monophyletic group whose range has expanded around a geographic barrier producing a ring‐shaped distribution. Populations that make up the ring should be contiguous and without barriers to gene flow except at one location where two reproductively isolated populations co‐occur. Ring species that meet this definition provide an opportunity for studying how speciation occurs through the gradual accrual of differences leading to reproductive isolation. However, few if any of the species that have a ring‐shaped distribution meet these requirements. The most studied species, greenish warbler Phylloscopus trochiloides and Ensatina eschscholtzii salamanders, fail to exhibit all of the characteristics of a strict ring species. However, the study of species with ring distributions has provided information about the processes that cause population divergence through time, and the use of new genomics and modelling tools could provide valuable insights into how geographic speciation, with or without adaptive divergence, could occur.

Key Concepts

  • Few organisms exhibit all of the requirements to be considered a true ring species.
  • Ring species are helpful tools that can be used to help elucidate evolutionary processes.
  • The preponderance of terrestrial and temperate ring species may be an ascertainment bias.
  • New methods in genomics and modelling will provide answers to questions about ring species formation and the processes of speciation.
  • Species from a wide range of taxa, other than birds and mammals, are now being examined as possible ring species.

Keywords: speciation; geographic variation; geographic speciation; Ensatina; greenish warbler; slipper spurge

Figure 1. Distribution of taxa identified by Stebbins , but with ranges based on molecular evidence (Wake, ).
Figure 2. Alternative models of ring species formation for song sparrows from Patten . In the models, song sparrows encounter the barrier and disperse around the barrier following the arrows. Differentiation around the ring is shown by differences in shading of the arrows and ecotones are shown with hash marks. The direction where birds originated before expansion is shown with small black arrows.
Figure 3. Diagrammatic representation of the origin of genetic incompatibility in a ring species. The ancestral population (purple) disperses southwards along both sides of a barrier. A mutation at the A locus occurs on one side of the barrier, whereas a mutation at the B locus occurs on the other side. The frequency of the mutant ‘a’ allele (blue colouration) and ‘b’ allele (red colouration) increases as populations disperse southward. Since ‘a’ and ‘b’ alleles are incompatible, sympatric populations fixed for them do not exchange genes (striped region).


Alcaide M, Scordato ESC, Price TD and Irwin DE (2014) Genomic divergence in a ring species complex. Nature 511: 83–85.

Allcock AL, Barratt I, Eléaume M, et al. (2011) Cryptic speciation and the circumpolarity debate: a case study on endemic Southern Ocean octopuses using the COI barcode of life. Deep Sea Research Part II: Topical Studies in Oceanography 58: 242–249.

Barrett RDH and Schluter D (2008) Adaptation from standing genetic variation. Trends in Ecology & Evolution 23: 38–44.

Bensch S, Grahn M, Muller N, et al. (2009) Genetic, morphological, and feather isotope variation of migratory willow warblers show gradual divergence in a ring. Molecular Ecology 18: 3087–3096.

Bonhomme F, Rivals E, Orth A, et al. (2007) Species‐wide distribution of highly polymorphic minisatellite markers suggests past and present genetic exchanges among house mouse subspecies. Genome Biology 8: R80.

Bowen BW, Bass AL, Rocha LA, et al. (2001) Phylogeography of the trumpetfishes (Aulostomus): ring species complex on a global scale. Evolution 55: 1029–1039.

Brain P (1989) Genetic races in a ring species, Acacia karroo. South African Journal of Science 85: 181–185.

Brown CW (1974) Hybridization among the subspecies of the plethodontid salamander Ensatina eschscholtzii. University of California Publications in Zoology 98: 9–20.

Cacho NI and Baum DA (2012) The Caribbean slipper spurge Euphorbia tithymaloides: the first example of a ring species in plants. Proceedings of the Royal Society B. DOI: 10.1098/rspb.2012.0498.

Cain AJ (1955) A revision of Trichoglossus haematodus and of the Australian platycercine parrots. Ibis 97: 432–479.

Coyne JA and Orr HA (2004) Speciation. Sunderland, MA: Sinauer Associates.

Devitt TJ, Baird SJE and Moritz C (2011) Asymmetric reproductive isolation between terminal forms of the salamander ring species Ensatina eschscholtzii revealed by fine‐scale genetic analysis of a hybrid zone. BMC Evolutionary Biology 11: 245.

Din W, Anand R, Boursot P, et al. (1996) Origin and radiation of the house mouse: clues from nuclear genes. Journal of Evolutionary Biology 9: 519–539.

Dressler R (1957) The Genus Pedilanthus (Euphorbiaceae). Contributions from the Gray Herbarium of Harvard University, vol. 182. Cambridge, MA: Harvard University Press.

Eastwood JR, Berg ML, Ribot RFH, et al. (2014) Phylogenetic analysis of beak and feather disease virus across a host ring‐species complex. Proceedings of the National Academy of Sciences of the United States of America 111: 14153–14158.

Gavrilets S, Li H and Vose MD (1998) Rapid speciation on holey adaptive landscapes. Proceedings of the Royal Society of London B 265: 1483–1489.

Highton R (1998) Is Ensatina a ring species? Herpetologica 54: 254–278.

Hoffmeister DF (1986) Mammals of Arizona. Tucson, AZ: University of Arizona Press and Arizona Game and Fish Department.

Irwin DE (2000) Song variation in an avian ring species. Evolution 54: 998–1010.

Irwin DE, Irwin JH and Price TD (2001) Ring species as bridges between microevolution and speciation. Genetica 112–113: 223–343.

Irwin DE (2002) Phylogeographic breaks without geographic barriers to gene flow. Evolution 56: 2383–2394.

Irwin DE and Irwin JH (2002) Circular overlaps: rare demonstrations of speciation. Auk 119: 596–602.

Irwin DE, Bensch S, Irwin JH and Price TD (2005) Speciation by distance in a ring species. Science 307: 414–416.

Jackman TR and Wake DB (1994) Evolutionary and historical analysis of protein variation in the blotched forms of salamanders of the Ensatina complex (Amphibia: Plethodontidae). Evolution 48: 876–897.

Jordan DS (1905) The origin of species through isolation. Science 22: 545–562.

Joseph L, Dolman G, Donnellan S, et al. (2008) Where and when does a ring start and end? Testing the ring‐species hypothesis in a species complex of Australian parrots. Proceedings of the Royal Society of London B 275: 2431–2440.

Kuchta SR, Parks DS, Mueller RL and Wake DB (2009) Closing the ring: historical biogeography of the salamander ring species Ensatina eschscholtzii. Journal of Biogeography 36: 982–995.

Liebers D, de Knijff P and Helbig AJ (2004) The herring gull complex is not a ring species. Proceedings of the Royal Society of London B 271: 893–901.

Martens J and Päckert M (2007) Ring species – Do they exist in birds? Zoologischer Anzeiger 246: 315–324.

Martins AB, de Aguiar MAM and Bar‐Yam Y (2013) Evolution and stability of ring species. Proceedings of the National Academy of Sciences of the United States of America 110: 5080–5084.

Mayr E (1963) Animal Species and Evolution, pp. 507–512. Cambridge, MA: Belknap Press.

McKnight ML (1995) Mitochondrial DNA phylogeography of Perognathus amplus and Perognathus longimembris (Rodentia: Heteromyidae): a possible mammalian ring species. Evolution 49: 816–826.

Monahan WB, Pereira RJ and Wake DB (2012) Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species. BMC Biology 10: 20.

Moritz C, Schneider CJ and Wake DB (1992) Evolutionary relationships within the Ensatina eschscholtzii complex confirm the ring species interpretation. Systematic Biology 41: 273–291.

Parks DS (2000) Phylogeography, Historical Distribution, Migration, and Species Boundaries in the Salamander Ensatina eschscholtzii as Measured with Mitochondrial DNA Sequences. Dissertation, University of California, Berkeley.

Patten MA, Rotenberry JT and Zuk M (2004) Habitat selection, acoustic adaptation, and the evolution of reproductive isolation. Evolution 58: 2144–2155.

Patten MA and Pruett CL (2009) The song sparrow as a ring species: patterns of geographic variation, a revision of subspecies, and implications for speciation. Systematics and Biodiversity 7: 33–62.

Patten MA (2010) Evolution and historical biogeography of a song sparrow ring in western North America. In P. Pontarotti (ed.) Evolutionary Biology–Concepts, Molecular and Morphological Evolution (pp. 329–342). Springer, Berlin.

Pereira RJ, Monahan WB and Wake DB (2011) Predictors for reproductive isolation in a ring species complex following genetic and ecological divergence. BMC Evolutionary Biology 11: 194.

Price TD, Helbig AJ and Richman AD (1997) Evolution of breeding distributions in the Old World leaf warblers (genus Phylloscopus). Evolution 51: 552–561.

Ribot RFH, Berg ML, Buchanan KL, et al. (2008) Does the ring species concept predict vocal variation in the crimson rosella, Platycercus elegans, complex? Animal Behaviour 77: 581–593.

Smyth JF, Patten MA and Pruett CL (2015) The evolutionary ecology of a species ring: a test of alternative models. Folia Zoologica 64: 233–244.

Stebbins RC (1949) Speciation in salamanders of the plethodontid genus Ensatina. University of California Publications in Zoology 48: 377–525.

Sternkopf V, Liebers‐Helbig D, Ritz MS, et al (2010) Introgressive hybridization and the evolutionary history of the herring gull complex revealed by mitochondrial and nuclear DNA. BMC Evolutionary Biology 10: 348.

Wake DB and Yanev KP (1986) Geographic variation in allozymes in a ‘ring species’, the plethodontid salamander Ensatina eschscholtzii of western North America. Evolution 40: 702–715.

Wake DB (1997) Incipient species formation in salamanders of the Ensatina complex. Proceedings of the National Academy of Sciences of the United States of America 94: 7761–7767.

Wake DB and Schneider CJ (1998) Taxonomy of the plethodontid salamander genus Ensatina. Herpetologica 54: 279–298.

Ward D (2011) Population differentiation in a purported ring species, Acacia karroo (Mimosoideae). Biological Journal of the Linnean Society 104: 748–755.

Watt JC (1983) Beetles (Coleoptera) of Auckland. Tane 29: 31–50.

Wink M, Kahl U and Heidrich P (1994) Genetic distinction of Larus argentatus, L. fuscus and L. cachinnans. Journal of Ornithology 135: 73–80.

Further Reading

Coyne JA and Orr HA (2004) Speciation. Sunderland, MA: Sinauer Associates.

Dobzhansky T (1937) Genetics and the Origin of Species. New York: Columbia University Press.

Mayr E (1970) Populations, Species and Evolution. Cambridge, MA: Belknap Press.

Price T (2008) Speciation in Birds. Greenwood Village, CO: Roberts and Company.

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Pruett, Christin L(Aug 2016) Ring Species and Speciation. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001751.pub4]