Aphids and Telescoping Generations

Aphid adult and nymphs (Photo credit: humbleseed.com)

If you could imagine an organism that gives birth to offspring that are already pregnant with a third generation, it would look something like a small, green, herbaceous insect. We call them aphids. As one of the world's worst agricultural pests, species of this group of insects exhibit a variety of peculiar reproductive strategies, including this phenomenon of telescoping generations. In many species, all of the overwintered eggs that hatch in the spring result in females, which then reproduce asexually to render generation after generation of genetically-identical female aphids (cyclical parthenogenesis). When autumn arrives, the females give live birth to both male and female offspring, lacking wings and often mouthparts. And upon sexual reproduction of these progeny, the females, rather than giving live birth (vivipary), lay eggs (ovipary) which overwinter and renew the cycle.

Because of the agricultural significance of this insect, scientists have sequenced the genome of one particular species, the Pea Aphid. Read the journal article here.