Extensive outcrossing and androdioecy in a vertebrate species that otherwise reproduces as a self-fertilizing hermaphrodite

doi:10.1073/pnas.0603847103

Extensive outcrossing and androdioecy in a vertebrate species that otherwise reproduces as a self-fertilizing hermaphrodite

*Department of Genetics, University of Georgia, Athens, GA 30602;
^‡Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697;
^§Brevard County Environmentally Endangered Lands Program, Melbourne, FL 32940; and
^¶Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

Contributed by John C. Avise, May 11, 2006
↵ ^†M.M. and A.T. contributed equally to this work.

Abstract

The mangrove killifish (Kryptolebias marmoratus) is the only vertebrate known to be capable of self-fertilization. Its gonad is typically an ovotestis that simultaneously produces eggs and sperm, and fertilization is internal. Although most populations of this species consist primarily or exclusively of hermaphroditic individuals, gonochoristic males occur at ≈20% frequency in a natural population at Twin Cays, Belize. Here we use a battery of 36 microsatellite loci to document a striking genetic pattern (high intraspecimen heterozygosities and low within-population linkage disequilibria) that differs qualitatively from the highly homozygous (or “clonal”) genetic architecture characteristic of killifish populations previously studied in Florida, where males are much rarer. These findings document that outcrossing (probably between gonochoristic males and hermaphrodites) is common at the Belize site, and, more importantly, they demonstrate the dramatic impact that functional androdioecy can have on the population genetic architecture of this reproductively unique vertebrate species.

Footnotes

^‖To whom correspondence should be addressed. E-mail: javise{at}uci.edu
Author contributions: B.J.T. and J.C.A. designed research; M.M., A.T., and D.S.T. performed research; A.T. analyzed data; and J.C.A. wrote the paper.
Conflict of interest statement: No conflicts declared.
Abbreviations:

Abbreviations:

FIS,

fixation indices;

HWE,

Hardy-Weinberg equilibrium;

LD,

linkage disequilibrium;

T,

outcrossing;

S,

selfing.