Teenagers can procreate. Terrified by this prospect, their parents often seek to exert whatever control they can over their children's sex lives. From a teenager's perspective it's all rather annoying having old farts incessantly minding your business. But before sighing heavily and rolling your eyes at mom's intrusions, spare a thought for the Japanese climbing fern. Compared to them you've got it easy.
Fully grown ferns are called gametophytes, and they can be males, females or hermaphrodites if there are no other breeders around to help out. But, of course, self-fertilization is the very incarnation of inbreeding, a situation to be avoided whenever possible.
So, when little fernlings are growing, older females in the neighborhood can secrete a chemical called gibberellin, which causes the surrounding youth to turn into males. Thus the grown-ups control the gender balance to maintain a healthy genetic diversity [source: Zastrow].
Of late, the word "community" has become a buzzword for all that is positive and necessary in 21st century life — perhaps the sex life of climbing ferns demonstrates that community involvement might have its limits!