Frequency- and density-dependent sexual selection in natural populations of Galician Littorina saxatilis Olivi

  • Emilio Rolán-Alvarez
  • Kerstin Johannesson
  • Anette Ekendahl
Conference paper
Part of the Developments in Hydrobiology book series (DIHY, volume 111)


Galician exposed shore populations of the direct developing periwinkle Littorina saxatilis are strikingly polymorphic, with an ornamented and banded upper shore form and a smooth and unhanded lower shore form. Intermediates between the two pure forms occur in a narrow mid shore zone together with the parental forms. We have previously shown that the two pure forms share the same gene pool but that mating between them is non-random. This is due to a non-random microdistribution in the zone of overlap, and also to assortative mating. In this study we present data which show that intermediate (hybrid) females mate less often than pure females in micropatches dominated by either of the pure forms, but not in micropatches in which the two pure forms are equally common. Thus, sexual fitness in intermediate females depends on the frequency of both pure morphs. Furthermore, sexual selection against intermediate females also varies with the densities of snails within each micro patch. The biological mechanisms which may explain this particular reduction of female hybrid fitness are discussed.

Assortative mating between the pure morphs is sometimes almost complete, while both morphs do not mate the intermediates assortatively. In the light of this, sexual selection against intermediate females may contribute considerably to restrict gene flow between the pure forms.

Key words

reproductive isolation mating components assortative mating sexual selection fitness estimate 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Allen, J. A., 1988. Frequency-dependent selection by predators. Phil. Trans, r. Soc., Lond. B 319: 485–503.CrossRefGoogle Scholar
  2. Antonovics, J. & P. Kareiva, 1988. Frequency-dependent selection and competition: empirical approaches. Phil. Trans. r. Soc., Lond. B 319: 601–613.CrossRefGoogle Scholar
  3. Butlin, R., 1987. Speciation by reinforcement. Trends in Ecology and Evolution 2: 8–13.PubMedCrossRefGoogle Scholar
  4. Butlin, R., 1989. Reinforcement of premating isolation. In D. Otte & J. A. Endler (eds), Speciation and its consequences. Sinauer, Sunderland, MA USA: 158–179.Google Scholar
  5. Christiansen, F. B., 1988. Frequency dependence and competition. Phil. Trans. r. Soc., Lond. B 319: 587–600.CrossRefGoogle Scholar
  6. Clarke, B. C., F. R. S. Shelton, P. R. Mani & G. S. Mani, 1988. Frequencydependent selection, metrical characters and molecular evolution. Phil. Trans. r. Soc., Lond. B 319: 631–640.CrossRefGoogle Scholar
  7. Cook, L. M., 1971. Coefficients of natural selection. Hutchinson University library, London.Google Scholar
  8. Coyne, J. A., 1992. Genetics and speciation. Nature 355: 511–515.PubMedCrossRefGoogle Scholar
  9. Endler, J. A., 1986. Natural selection in the wild. Princenton University Press, Princenton.Google Scholar
  10. Erlandsson, J. & K. Johannesson, (in press). Sexual selection on female size in a marine snail, Littorina littorea (L.). J. exp. mar. Biol. Ecol.Google Scholar
  11. Gilbert, D. G. & W. T. Starmer, 1985. Statistics of sexual isolation. Evolution 39: 1380–1383.CrossRefGoogle Scholar
  12. Johannesson, K., B. Johannesson & E. Rolán-Alvarez, 1993. Morphological differentiation and genetic cohesiveness over a microenvironmental gradient in the marine snail Littorina saxatilis. Evolution 47: 1770–1787.CrossRefGoogle Scholar
  13. Johannesson, K., E. Rolán-Alvarez & A. Ekendahl, (in press). Incipient reproductive isolation between two sympatric morphs of the intertidal snail Littorina saxatilis. Evolution.Google Scholar
  14. Knoppien, P., 1985. Rare male mating advantage: a review. Biol. Rev. 60: 81–117.CrossRefGoogle Scholar
  15. Marin, I., 1991. Sexual isolation in Drosophila, I. Theoretical models for multiple-choice experiments. J. theor. Biol. 152: 271–284.Google Scholar
  16. Merrel, D. J. 1950. Measurement of sexual isolation and selective mating. Evolution 4: 326–331.CrossRefGoogle Scholar
  17. O’Donald, P., 1980. Genetic models of sexual selection. Cambridge University Press, London.Google Scholar
  18. O’Donald, P. & M. E. N. Majerus, 1988. Frequency-dependent sexual selection. Phil. Trans. r. Soc., Lond. B 319: 571–586.CrossRefGoogle Scholar
  19. Partridge, L., 1988. The rare-male effect: what is its evolutionary significance? Phil. Trans. r. Soc., Lond. B 319: 525–539.CrossRefGoogle Scholar
  20. Rolán-Alvarez, E. 1993. Estructura genética y selección sexual en poblaciones naturales de dos especies gemelas del género Littorina. Ph. D. Thesis, University of Santiago, Spain.Google Scholar
  21. Santos, M., R. Tarrio, C. Zapata & G. Alvarez. 1986. Sexual selection on chromosomal polymorphism in Drosophila subobscura. Heredity 57: 161–169.CrossRefGoogle Scholar
  22. Saur, M. 1990. Mate discrimination in Littorina littorea (L.) and L. saxatilis (Olivi) (Mollusca: Prosobranchia). Hydrobiologia 193(Dev. Hydrobiol. 56): 261–270.CrossRefGoogle Scholar
  23. Spieth, H. T. & J. M. Ringo, 1983. Mating behavior and sexual isolation in Drosophila. In M. Ashburner, H. L. Carson & J. N. Thompson (eds), The genetics and biology of Drosophila, 3c. Academic Press, London: 224–284.Google Scholar
  24. Sundberg, P. 1988. Microgeographic variation in shell characters of L. saxatilis Olivi-a question mainly of size? Biol. J. linn. Soc. 35: 169–184.CrossRefGoogle Scholar
  25. Zaykin, D. V. & A. I. Pudovkin, 1993. Two programs to estimate significance of x2 values using pseudo-probability tests. J. Hered. 84: 152.Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1995

Authors and Affiliations

  • Emilio Rolán-Alvarez
    • 1
  • Kerstin Johannesson
    • 2
  • Anette Ekendahl
    • 2
  1. 1.Unidad de Genética, Biológicas Módulo A 201Universidad Autónoma de Madrid (Cantoblanco)MadridSpain
  2. 2.Tjärnö Marine Biological LaboratoryStrömstadSweden

Personalised recommendations