Authors: NORMARK, BENJAMIN B.¹; JUDSON, OLIVIA P.²; MORAN, NANCY A.³

Source: Biological Journal of the Linnean Society, Volume 79, Number 1, May 2003 , pp. 69-84(16)

Publisher: Wiley-Blackwell

Abstract:

Ancient asexuals - organisms that have lived without sex for millions of years - offer unique opportunities for discriminating among the various theories of the maintenance of sex. The last few years have seen molecular studies of a number of putative ancient asexual lineages, including bdelloid rotifers, Darwinulid ostracods, and mycorrhizal fungi. To help make sense of the diverse findings of such studies, we present a review and classification of the predicted effects of loss of sex on the eukaryotic genome. These include: (1) direct effects on the genetic structure of individuals and populations; (2) direct effects on the mutation rate due to the loss of the sexual phase; (3) decay of genes specific to sex and recombination; (4) effects of the cessation of sexual selection; (5) dis-adaptation due to the reduced efficiency of selection; and (6) adaptations to asexuality. We discuss the utility of the various predictions for detecting ancient asexuality, for testing hypotheses of the reversibility of a transition to asexuality, and for discriminating between theories of sex. In addition, we review the current status of putative ancient asexuals. © 2003 The Linnean Society of London. Biological Journal of the Linnean Society 2003, 79, 69-84.

Keywords: adaptation; bdelloid rotifers; Darwinulid ostracods; eukaryotic genome; molecular studies; mycorrhizal fungi; selection; sex

Document Type: Research article

DOI: http://dx.doi.org/10.1046/j.1095-8312.2003.00182.x

Affiliations: 1: Department of Entomology, University of Massachusetts, Amherst, MA 01003, USA 2: Department of Biological Sciences, Imperial College, Exhibition Road, London, UK 3: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA

Publication date: 2003-05-01

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