Destabilizing Hybridization, General-Purpose Genotypes and Geographic Parthenogenesis

Abstract

The ecological and genetic correlates of parthenogenesis are clarified by focusing upon two of the major challenges that confront a newly arisen parthenogen: the genetic disruption that results from backcrosses with sexual relatives, and the evolution of a highly generalized genotype. Both of these factors have been ignored in previous theories of the evolution of reproductive systems. Yet, the geographic ranges, ecological characteristics, elevated ploidy levels, and hybrid origins of many parthenogens, as well as the widespread suppression of recombination in automicts, are consistent with expectations derived from the destabilizing hybridization and general-purpose genotype hypotheses. Whereas the support for these hypotheses is broad, much of the evidence is circumstantial; experimental tests would allow an evaluation of the proposed hypotheses and the more traditional alternatives based on differential colonization, competitive, and coevolutionary abilities. An appreciation of the stringent requirements for a successful transition to parthenogenesis may help to explain its uneven phylogenetic distribution. The relevance of parthenogenesis to the biological control of pest species also requires attention.