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A TEST OF THE SPONTANEOUS HETEROSIS HYPOTHESIS FOR UNISEXUAL VERTEBRATES
Author(s) -
Wetherington Jeffrey D.,
Kotora Karen E.,
Vrijenhoek Robert C.
Publication year - 1987
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1987.tb05848.x
Subject(s) - biology , heterosis , hybrid , ploidy , natural selection , evolutionary biology , sympatric speciation , loss of heterozygosity , poeciliidae , sexual reproduction , zoology , genetics , ecology , allele , botany , gene , selection (genetic algorithm) , fish <actinopterygii> , fishery , artificial intelligence , computer science
The coupling between clonal modes of reproduction and hybridization in unisexual vertebrates has led to the hypothesis that heterosis accounts for their ecological success (the “spontaneous heterosis” hypothesis). High levels of genic heterozygosity characteristic of unisexual‐hybrid vertebrates are believed to result in enhanced growth, survivorship, and fertility relative to their sexual ancestors. To test this hypothesis, we synthesized 33 new unisexual‐hybrid strains of fishes in the genus Poeciliopsis (Atheriniformes: Poeciliidae). On average, the synthetic unisexuals had lower survivorship and a higher incidence of birth defects than either of the sexual ancestors or two natural strains of unisexuals. However, a subset of these synthetic unisexuals exhibited characteristics within the range of the sexual ancestors and natural unisexual strains. These results support the alternative hypothesis that the ecological success of natural unisexuals results from selection of the most fit clones from a broad spectrum of genotypes that arose via multiple hybrid events. We propose that the coupling between unisexuality and hybridization in the vertebrates exists because hybridization is a dysgenic process that can disrupt normal gametogenesis and thus lead to clonal reproduction.