SELFISH GENETIC ELEMENTS AND THEIR ROLE IN EVOLUTION - THE EVOLUTION OF SEX AND SOME OF WHAT THAT ENTAILS

An individual is often considered (sometimes implicitly) to be the pro duct of a well functioning mutualism between its constituent genes. Th is however need not be so. One consequence of sexual reproduction is t hat costly competition within an individual between genes that are eff ectively allelic can provide the conditions for the spread of suppress ors of such competition. The spread of both these ultracompetitive all eles (alias selfish genetic elements) and their suppressors is evidenc e of a 'conflict of interests' within the genome. That this conflict i s a potentially important force in the evolution of genetic systems is illustrated by consideration of the problem of the evolution of sexes (alias mating types). One hypothesis holds that sexes are the result of selection on nuclear genes to coordinate the inheritance of cytopla smic genomes (usually this means the enforcement of uniparental inheri tance) so as to prevent competition between unrelated cytoplasmic geno mes. This hypothesis is tested against five comparative predictions an d shown to receive considerable empirical support.