Reevolution of sexuality breaks Dollo's law

^†Institut für Zoologie, Technische Universität Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany; and
^§College of Environmental Science and Forestry, State University of New York, 1 Forestry 16 Drive, Syracuse, NY 13210

Edited by John C. Avise, University of California, Irvine, CA, and approved March 8, 2007 (received for review January 3, 2007)

Abstract

The dominance of sexual reproduction is still an unresolved enigma in evolutionary biology. Strong advantages of sex have to exist, because only a few parthenogenetic taxa persist over evolutionary timescales. Oribatid mites (Acari) include outstanding exceptions to the rule that parthenogenetically reproducing taxa are of recent origin and doomed to extinction. In addition to the existence of large parthenogenetic clusters in oribatid mites, phylogenetic analyses of this study and model-based reconstruction of ancestral states of reproduction imply that Crotoniidae have reevolved sexuality from parthenogenetic ancestors within one of those clusters. This reversal in reproductive mode is unique in the animal kingdom and violates Dollo's law that complex ancestral states can never be reacquired. The reevolution of sexuality requires that ancestral genes for male production are maintained over evolutionary time. This maintenance likely is true for oribatid mites because spanandric males exist in various species, although mechanisms that enable the storage of genetically ancestral traits are unclear. Our findings present oribatid mites as a unique model system to explore the evolutionary significance of parthenogenetic and sexual reproduction.

Footnotes

^‡To whom correspondence should be addressed. E-mail: katjadomes{at}gmx.de
Author contributions: R.A.N. designed research; K.D. performed research; R.A.N. contributed new reagents/analytic tools; K.D. analyzed data; and K.D., R.A.N., M.M., and S.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS direct submission.
Data deposition footnote: The sequences reported in this paper have been deposited in the National Center for Biotechnology Information databank, www.ncbi.nlm.nih.gov (accession nos. AF022027, AF022036, AF022040, AY573591, AY632776, AY632825, AY632837, AY632851, AY632861, DQ090773, DQ090776, DQ090777, DQ090779–83, DQ090786, DQ090789, DQ090793–DQ090802, EF081297–EF081339, EF091416–EF091429, EF093763, EF093770, and EF093781).
This article contains supporting information online at www.pnas.org/cgi/content/full/0700034104/DC1.
Abbreviations:

ML,

maximum likelihood;

MP,

maximum parsimony;

NJ,

neighbor joining.