Environmental Biology of Fishes

, Volume 88, Issue 2, pp 201–206 | Cite as

Equal fecundity in asexual and sexual mollies (Poecilia)

  • Ingo Schlupp
  • Angelika Taebel-Hellwig
  • Michael Tobler


The evolution and maintenance of sexual reproduction is still one of the major unresolved problems in evolutionary biology. Sexual reproduction is fraught with a number of costs as compared to asexual reproduction. For example, sexuals have to produce males, which–given a 1:1 sex ratio—results in a two-fold advantage for asexuals that do not produce males. Consequently, asexuals will outperform and replace sexuals over time assuming everything else is equal. Nonetheless, a few cases of closely related asexuals and sexuals have been documented to coexist stably in natural systems. We investigated the presence of a two-fold cost in a unique system of three closely related fish species: the asexual Amazon Molly (Poecilia formosa), and two sexual species, Sailfin Molly (P. latipinna) and Atlantic Molly (P. mexicana). Amazon Molly reproduce gynogenetically (by sperm dependent parthenogenesis) and always coexist with one of the sexual species, which serves as sperm donor. In the laboratory, we compared reproductive output between P. formosa and P. mexicana as well as P. formosa and P. latipinna. We found no differences in the fecundity in either comparison of a sexual and the asexual species. Under the assumption of a 1:1 sex ratio, the asexual Amazon Molly should consequently have a full two-fold advantage and be able to outcompete sexuals over time. Hence, the coexistence of the species pairs in nature presents a paradox still to be solved.


Poeciliid Asexual Recombination Fecundity 



We are grateful to the Aquarium Team in Hamburg for fish care, J. Parzefall for helpful discussions. Financial support was provided by the DFG (Schl 344-10-1,2) and the University of Oklahoma (to IS) as well as the Basler Foundation for Biological Research, the Janggen-Poehn-Foundation, the Roche Research Foundation, and the Wolfermann-Nägeli-Foundation (to MT). Texas Parks & Wildlife kindly issued a collection permit (SPR-0305-045). Experiments at the University of Oklahoma were conducted under IACUC AUS R05-014. M. Plath and R. Riesch kindly commented on an earlier version of the manuscript.


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Ingo Schlupp
    • 1
    • 3
  • Angelika Taebel-Hellwig
    • 1
  • Michael Tobler
    • 2
  1. 1.Universität Hamburg, Zoologisches Institut und Zoologisches MuseumHamburgGermany
  2. 2.Departments of Biology and Wildlife and Fisheries SciencesTexas A&M UniversityCollege StationTXUSA
  3. 3.Department of ZoologyUniversity of OklahomaNormanUSA

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