Ecology and evolution of sex in aphids

Many theories attempt to explain why sexual reproduction has invaded life so thoroughly. Some are plausible, but there remains a need for evolutionary biologists to identify the main factor(s) accounting for the maintenance of sex in diverse, real organisms. An increasing focus of studies on the evolution of sex concerns cyclical parthenogens and aphids in particular, which conveniently show coexistence of sexual and asexual reproductive modes. Recent research has shown a major short-term advantage of sex in aphids to be purely ecological: the production of cold-resistant eggs. However, this is unlikely to be the only force acting to maintain sex in aphids. In the past five years, theoretical developments and the accumulation of ecological and molecular data have greatly advanced understanding of the genetic and evolutionary consequences of reproductive modes in aphids and their distributions in nature, and they have provided tools that promise to make aphids important organisms with which to examine general advantages of sex.