Speciation by Distance in a Ring Species

  title={Speciation by Distance in a Ring Species},
  author={Darren E. Irwin and Staffan Bensch and Jessica H. Irwin and Trevor D. Price},
  pages={414 - 416}
Ring species, which consist of two reproductively isolated forms connected by a chain of intergrading populations, have often been described as examples of speciation despite gene flow between populations, but this has never been demonstrated. We used amplified fragment length polymorphism (AFLP) markers to study gene flow in greenish warblers (Phylloscopus trochiloides). These genetic markers show distinct differences between two reproductively isolated forms but gradual change through the… 
Genomic divergence in a ring species complex
Genome-wide analyses show that, although spatial patterns of genetic variation are currently mostly as expected of a ring species, historical breaks in gene flow have existed at more than one location around the ring, and the two Siberian forms have occasionally interbred, casting doubt on the hypothesis that the greenish warbler should be viewed as a rare example of speciation by distance.
The role of sex separation in neutral speciation
It is shown that for a particular carrying capacity, speciation occurs under similar conditions, but the number of species generated is lower than in the hermaphroditic case, and the species–area curve has lower exponents, especially at intermediate scales.
Ring Species and Speciation
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.
Evolutionary genetics: A ring of species
A long-standing model illustrating how new species can arise through ‘circular overlap’, without interruption of gene flow through intervening populations, has now been confirmed among passerine birds (Irwin et al, 2005), and the new study of the Eurasian greenish warbler complex provides the most convincing case to date in support of the ring species model.
Where and when does a ring start and end? Testing the ring-species hypothesis in a species complex of Australian parrots
It is suggested that selection and drift now drive evolution in different populations within what has been considered the ring, and alternative models involving historical allopatry of populations are discussed.
Barriers to gene flow and ring species formation
This model simulates the evolution of ring species assuming that individuals become sexually isolated if the genetic distance between them is above a certain threshold, and incorporates two forms of dispersal limitation: exogenous geographic barriers that limit the population range and endogenous barriers that result in genetic structuring within the populationrange.
The evolutionary ecology of a species ring: a test of alternative models
Song sparrows do fit some aspects of a classic ring species that formed via expansion around a barrier; however, admixture rather than complete reproductive isolation occurred when populations met at the terminus of the ring in southern California.
Diploid versus haploid models of neutral speciation
This work discusses the implementation of two schemes of dominance to analyze the effects of diploidy: a complete dominance model in which one allele dominates over the other and a perfect codominant model inwhich heterozygous genotypes give rise to a third phenotype.
Reproductive isolation and patterns of genetic differentiation in a cryptic butterfly species complex
Comparisons of genetic divergence across western Eurasia in an extensive data set of mitochondrial and nuclear DNA sequences with behavioural data on inter‐ and intraspecific reproductive isolation in courtship experiments suggest that additional hidden diversity is unlikely to occur in Europe.
Cryptic speciation in a Holarctic passerine revealed by genetic and bioacoustic analyses
It is indicated that the two forms are reproductively isolated to a high degree where they co‐occur and are therefore separate species, and it is suggested that sexual selection played a larger role than habitat divergence in generating reproductive isolation.


Speciation in a ring
This work reconstructs the pathway to speciation between two reproductively isolated forms of greenish warbler and shows how gradual divergence in a trait involved in mate choice leads to theformation of new species.
  • D. Irwin
  • Biology, Environmental Science
    Evolution; international journal of organic evolution
  • 2000
It is suggested that parallel south-to-north ecological gradients have caused a greater intensity ofSexual selection on song in northern populations and that the stochastic effects of sexual selection have led to divergence in song structure.
Speciation along environmental gradients
It is shown that along an environmental gradient, evolutionary branching can occur much more easily than in non-spatial models, and this facilitation is most pronounced for gradients of intermediate slope.
Rapid parapatric speciation on holey adaptive landscapes
It is demonstrated that rapid speciation on the time–scale of hundreds of generations is plausible without the need for extreme founder events, complete geographic isolation, the existence of distinct adaptive peaks or selection for local adaptation, and the plausibility of speciation is enhanced by population subdivision.
A role for ecotones in generating rainforest biodiversity
Results suggest that natural selection may play an important role in generating rainforest biodiversity and that ecotone habitats may be a source of evolutionary novelty.
Evolution of ecological differences in the Old World leaf warblers
A phylogeny is used for eight sympatric species of warbler in the genusPhylloscopus, based on their mitochondrial DNA sequences, to remove the effects of historical legacy, and finds strong support for adaptive interpretations of among-species variation in habitat selection, prey-size choice and feeding method.
A test of alternative models of diversification in tropical rainforests: ecological gradients vs. rainforest refugia.
It is indicated that natural selection operating across ecological gradients can be more important than geographic isolation in similar habitats in generating phenotypic diversity and selection is sufficiently strong to overcome the homogenizing effects of gene flow, a necessary first step toward speciation in continuously distributed populations.
Dark habitats and bright birds illustrate the role of the environment in species divergence
This study shows that variation in the physical environment can cause species divergence, and this will occur whether perceptual systems are variable or relatively constant.
Instability of the sexual continuum
  • A. Noest
  • Physics
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 1997
Maynard Smith and Szathmary have posed the problem of demonstrating the conjectured instability of a continuum of sexual types with finite interbreeding. Here, I propose a model in which one can
Examination of the effects of body mass and habitat structure on variation in song structure of 30 taxa of Phylloscopus and Hippolais warblers found that species occupying closed habitats avoided the use of rapidly modulated signals and had song structures that minimized reverberation.