, Volume 546, Issue 1, pp 29–45 | Cite as

Speciation and Selection without Sex

  • C. William BirkyJr.Email author
  • Cynthia Wolf
  • Heather Maughan
  • Linnea Herbertson
  • Elena Henry


More than 100 females of the obligately asexual bdelloid rotifers were isolated from nature and their mitochondrial cox1 genes (encoding cytochrome oxidase subunit 1) were sequenced. Phylogenetic analysis of the sequences showed that most of the isolates fall into 21 clades that show two characteristics of species: they are reciprocally monophyletic and have sequence diversities similar to that of species in other organisms. These clades have been evolving independently in spite of being effectively sympatric, indicating that they are adapted to different ecological niches. In support of this, at least some of the clades differ in morphology, food utilization, and temperature tolerance. We conclude that the bdelloid rotifers have undergone substantial speciation in the absence of sexual reproduction. We also used these sequences to test the prediction that asexual organisms should be subject to relaxed natural selection and hence will accumulate detrimental mutations. In contrast to this prediction, several estimates of the ratio Ka/Ks for the cox1 gene showed that this gene is subject to strong selection in the bdelloid rotifers.


cladogenesis speciation asexual reproduction bdelloid rotifer natural selection 


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Copyright information

© Springer 2005

Authors and Affiliations

  • C. William BirkyJr.
    • 1
    Email author
  • Cynthia Wolf
    • 2
    • 3
  • Heather Maughan
    • 4
    • 5
  • Linnea Herbertson
    • 6
    • 7
  • Elena Henry
    • 8
    • 9
  1. 1.Department of Ecology and Evolutionary Biology and Graduate Interdisciplinary Program in GeneticsThe Universityof Arizona, Biological Sciences WestTucsonUSA
  2. 2.Department of Molecular and Cellular BiologyThe University of Arizona,Biological Sciences WestTucsonUSA
  3. 3.Program in Genetic CounselingThe University of Texas Graduate School of Biomedical SciencesHoustonUSA
  4. 4.Graduate Interdisciplinary Program in GeneticsThe University of Arizona, Biological Sciences WestTucsonUSA
  5. 5.Department of Ecology and Evolutionary BiologyThe University of Arizona, Biological Sciences WestTucsonUSA
  6. 6.Department of Ecology and Evolutionary BiologyThe University of Arizona,Biological Sciences WestTucsonUSA
  7. 7.Aqauria, Inc. Moorpark93021
  8. 8.Department of Molecular and Cellular BiologyThe University of Arizona,Biological Sciences WestTucsonUSA
  9. 9.Elena HenrySierra VistaUSA

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