I never stopped to think about this, but I was reading the September 2009 edition of and came across an article on plant sex, in particular, orchid sex. It’s easy for our brains to understand how mammals reproduce, because it’s similar to how we reproduce. Plants, however, it’s a whole different ball game. They’re stationary, so how do they do it?! Are there even male and female plants?
“Hoping to observe some of this plant sex, I went in search of one of the most ingenious and diabolical of orchids; the Ophyrs (some botanists call it the prostitute orchid). I’d been eager to lay eyes on this orchid and meet its hapless pollinator ever since reading about its reproductive strategy, which involves what my field guide referred to as sexual deception and pseudocopulation. In the case of this particular Ophyrs, that animal is a relative of the bumblebee. The orchid offers no nectar or pollen reward; rather it seduces male bees with the promise of bee sex and then insures its pollination by frustrating precisely the desire it has excited. The orchid accomplishes its sexual deception by mimicking the appearance, scent, and even the tactile experience of a female bee …
When it comes to getting an orchid pollinated, sexual deception has an uneven success rate, but when it does work, it works like this: the real male bee alights on the beelike-labellum and attempts to mate, or in the words of one botanical reference, begins performing movements which look like an abnormally vigorous and prolonged attempt at copulation. In the midsts of these fruitless exertions, the bee jostles the orchid’s column (a structure that houses both the male and female sexual organs), and two yellow sacs packed with pollen (called the pollinia) are struck to his back with a quick-drying glue-like substance. Frustration mounts, until eventually it dawns on the bee that he has been had. He abruptly flies off, pollinia firmly attached, in frantic search of more authentic female companionship.
There was something poignant about the bee I spotted, flying around madly with what looked like a chubby pair of yellow oxygen tanks strapped to his back. He’d been deluded by the promise of sex – bee sex – when in fact all that was on offer was plant sex, and unbeknownst to the bee, now searching for a second, more satisfactory liaison, he was right in the middle of that act. Botanists have been known to refer to pollen-carrying bees as ‘flying penises.’
Why haven’t all orchids stuck with the more straightforward pollination strategies based on nectar rewards? And how in the world did their sexual practices get so elaborate? As for the hoodwinked pollinators, what, if anything, do they gain? If the answer is nothing but frustration, then why wouldn’t natural selection eventually weed out insects so foolhardy as to spend their time mating with nature’s version of the inflatable love doll? John Alcock, an evolutionary biology offers an explanation. When botanists experimented by adding a nectar reward to a normally nectarless orchid, they found that the pollinators hung around longer, happily visiting other blooms on the same and nearby plants. This does not suit the orchid’s interests, however, since inbreeding results in lower quality seeds. By comparison, outcrossing, or mixing one’s genes with distant mates, increases vigor and variation in one’s offspring, maximizing fitness. The sexual frustration of a deluded bee turns out to be an essential part of the orchid’s reproductive strategy. Determined not to make the same mistake again, the bee travels some distance and, if things work out for the orchid, ends up pseudocopulating (leaving his package of pollen) with an orchid a ways off. That distant orchid is likely to look and smell ever so slightly different from the first, and some botanists believe these subtle variations from plant to plant are part of the orchid’s strategy to prevent bees from learning not to fall for a flower.
The tongue orchid (Cryptostylis) lures its pollinator by deploying a scent closely resembling the pheromone of the female wasp (lissopimpla excelsa). The male wasp alights on the tonguelike labellum, tail first and commences to copulate with the flower, probing its interior with the tip of his abdoment until it bumps into the sticky pollinia, which attach themselves to the insect’s posterior like a pair of yellow tails. Having to play pin the tail on the pollinator is only the beginning of the wasp’s humiliation. For with the tongue orchid we have passed beyond pseudocupulation into a realm even more perverse: more often than not, the wasp in the throes of his misguided sexual exertions, actually ejaculates onto the flower. Sure this represents the height of maladaptive behavior, and natural selection could be expected to deal harshly with a creature foolish enough to squander its genes having sex with a flower. But as with so much else in thie bizarre world of orchid sex, the matter is not quite so simple. It appears that in some insect species, such as Lissopimpla excelsa, females can reproduce with or without sperm from a male. With it, they produce the usual ratio of male and female offspring, without sperm, they produce only male offspring. How convenient – for the tongue orchid, that is. By inducing wasps to waste their sperm on its flowers, tongue orchids are decreasing the amount of sperm available to female wasps, thereby assuring themselves an even larger population of pollinators. Not only that, but the overabundance of male wasps increases competition for females, which makes the desperate wasps less picky in their choice of mates and that much more likely to fall for a flower.”
– Michael Pollan
