---
_id: '4321'
abstract:
- lang: eng
  text: 'The fire-bellied toads Bombina bombina and B. variegata differ extensively
    in biochemistry, morphology, and behavior. We use a survey of five diagnostic
    enzyme loci across the hybrid zone near Cracow in Southern Poland to estimate
    the dispersal rate, selection pressures, and numbers of loci which maintain this
    zone. The enzyme clines coincide closely with each other and with morphological
    and mitochondrial DNA clines. Although the zone lies on a broad transition between
    environments suitable for bombina and variegata, the close concordance of diverse
    characters, together with increased aberrations and mortality in hybrids, suggest
    that the zone is maintained largely by selection against hybrids. There are strong
    “linkage disequilibria” between each pair of (unlinked) enzyme loci (R̄ = 0.129
    [2-unit support limits: 0.119–0.139]). These are probably caused by gene flow
    into the zone, and they give an estimate of dispersal (σ = 890 [790–940] m gen−½).
    The clines are sharply stepped, with most of the change occurring within 6.15
    (5.45–6.45) km, but with long tails of introgression on either side. This implies
    that the effective selection pressure on each enzyme marker (due largely to disequilibrium
    with other loci) is s* = 0.17 (0.159–0.181) at the center but that the selection
    acting directly on the enzyme loci is weak or zero (se < 0.0038). The stepped
    pattern implies a barrier to gene flow of 220 (48–415) km. This would substantially
    delay neutral introgression but would have little effect on advantageous alleles;
    the two taxa need not evolve independently. Strong selection is needed to maintain
    such a barrier: hybrid populations must have their mean fitness reduced by a factor
    of 0.65 (0.60–0.77). This selection must be spread over a large number of loci
    to account for the concordant patterns and the observed cline widths (N = 300
    [80–2,000]).'
acknowledgement: 'We are grateful to J. Mitton and W. P. Hall for their suggestions
  and help with earlier versions of the statistical analysis. The manuscript was much
  improved by the helpful comments of Dorothy Currie, Gunther Gollmann, Godfrey Hewitt,
  Julian MacLean, and Jim Mallet. Thanks are also due to Tina Tsang for her careful
  typing. This work was supported by  the Exchange Agreement between the Polish Academy
  of Sciences and the Royal Society, and by grants from the Polish Academy of Sciences
  (project MR-II/6), the Royal Society, the Nuffield Foundation, and the  Science
  and Engineering Research Council. '
article_processing_charge: No
article_type: original
author:
- first_name: Jacek
  full_name: Szymura, Jacek
  last_name: Szymura
- first_name: Nicholas H
  full_name: Barton, Nicholas H
  id: 4880FE40-F248-11E8-B48F-1D18A9856A87
  last_name: Barton
  orcid: 0000-0002-8548-5240
citation:
  ama: Szymura J, Barton NH. Genetic analysis of a hybrid zone between the fire-bellied
    toads Bombina bombina and B. variegata, near Cracow in Southern Poland. <i>Evolution;
    International Journal of Organic Evolution</i>. 1986;40:1141-1159. doi:<a href="https://doi.org/10.1111/j.1558-5646.1986.tb05740.x">10.1111/j.1558-5646.1986.tb05740.x</a>
  apa: Szymura, J., &#38; Barton, N. H. (1986). Genetic analysis of a hybrid zone
    between the fire-bellied toads Bombina bombina and B. variegata, near Cracow in
    Southern Poland. <i>Evolution; International Journal of Organic Evolution</i>.
    Society for the Study of Evolution. <a href="https://doi.org/10.1111/j.1558-5646.1986.tb05740.x">https://doi.org/10.1111/j.1558-5646.1986.tb05740.x</a>
  chicago: Szymura, Jacek, and Nicholas H Barton. “Genetic Analysis of a Hybrid Zone
    between the Fire-Bellied Toads Bombina Bombina and B. Variegata, near Cracow in
    Southern Poland.” <i>Evolution; International Journal of Organic Evolution</i>.
    Society for the Study of Evolution, 1986. <a href="https://doi.org/10.1111/j.1558-5646.1986.tb05740.x">https://doi.org/10.1111/j.1558-5646.1986.tb05740.x</a>.
  ieee: J. Szymura and N. H. Barton, “Genetic analysis of a hybrid zone between the
    fire-bellied toads Bombina bombina and B. variegata, near Cracow in Southern Poland,”
    <i>Evolution; International Journal of Organic Evolution</i>, vol. 40. Society
    for the Study of Evolution, pp. 1141–1159, 1986.
  ista: Szymura J, Barton NH. 1986. Genetic analysis of a hybrid zone between the
    fire-bellied toads Bombina bombina and B. variegata, near Cracow in Southern Poland.
    Evolution; International Journal of Organic Evolution. 40, 1141–1159.
  mla: Szymura, Jacek, and Nicholas H. Barton. “Genetic Analysis of a Hybrid Zone
    between the Fire-Bellied Toads Bombina Bombina and B. Variegata, near Cracow in
    Southern Poland.” <i>Evolution; International Journal of Organic Evolution</i>,
    vol. 40, Society for the Study of Evolution, 1986, pp. 1141–59, doi:<a href="https://doi.org/10.1111/j.1558-5646.1986.tb05740.x">10.1111/j.1558-5646.1986.tb05740.x</a>.
  short: J. Szymura, N.H. Barton, Evolution; International Journal of Organic Evolution
    40 (1986) 1141–1159.
date_created: 2018-12-11T12:08:14Z
date_published: 1986-01-01T00:00:00Z
date_updated: 2022-01-31T15:31:37Z
day: '01'
doi: 10.1111/j.1558-5646.1986.tb05740.x
extern: '1'
intvolume: '        40'
language:
- iso: eng
month: '01'
oa_version: None
page: 1141 - 1159
publication: Evolution; International Journal of Organic Evolution
publication_identifier:
  eissn:
  - 1558-5646
  issn:
  - 0014-3820
publication_status: published
publisher: Society for the Study of Evolution
publist_id: '1724'
quality_controlled: '1'
status: public
title: Genetic analysis of a hybrid zone between the fire-bellied toads Bombina bombina
  and B. variegata, near Cracow in Southern Poland
type: journal_article
user_id: ea97e931-d5af-11eb-85d4-e6957dddbf17
volume: 40
year: '1986'
...