Television sure seems obsessed with a post-apocalyptic planet -- and you can't throw a remote without hitting a zombie these days. I admit that it's certainly hard not to be intrigued. What would it be like if most of humanity were gone? What would life on Earth be like if zombies ran the roost?
Well, from the perspective of the living environment a zombie-dominated world may not be so bad.
As far as I can tell, zombies take no interest in nature -- they just look for humans to eat. That is bad for Homo sapiens, but seems like a pretty good deal for the rest of Earth's species. On The Walking Dead, the birds are chirping with so much gusto that you can just tell they like how things have turned out.
Plants can't sing about it, but I'd wager that most of them would also be pleased about a zombie apocalypse. Zombies don't mow the lawn or douse it with herbicides. They don't cut down trees to build houses or to make charcoal. Contrary to the central plot of the Plants vs. Zombies video games, these two classes of beings probably have little to fight about. In fact, even in the current non-zombie times there are plants that have a lot in common with the undead.
One of these plant species, skunk cabbage, is the subject of the latest episode of the "Plants Are Cool, Too!" video series. Skunk cabbage, known to science as Symplocarpus foetidus, uses two chemicals called cadaverine and putrescine to emulate the odor of rotting flesh. Whereas many flowers draw in insect pollinators with flowery scents that might make for an attractive perfume, those of skunk cabbage are meant to bring in insects that prefer something meatier.
If you've ever witnessed maggots on an animal carcass, you already know much of the story. Those maggots will grow up to be adult flies who will do what their moms did for them: find a dead critter (or other suitably gross pile of decaying organic matter) and lay eggs in it. As the eggs hatch, the young fly larvae (maggots) are born into their food source. Skunk cabbage uses this insect life cycle to its advantage, hoping to fool an insect looking for a brood site into stopping in to check out its flowers.
This mechanism for attracting pollinators is called sapromyophily. It is defined by the plant's ability to deceive insects by mimicking dead and decaying things, including carcasses, animal feces, and (perhaps someday) wandering zombies.
Rather than being an exception, skunk cabbage is one of a number of sapromyophilous species worldwide, occurring in at least four different plant families. In other words, sapromyophily is a fairly common way that insects looking to lay eggs are being tricked into visiting stinky flowers -- and thus moving pollen around.
Some of the most impressive plant reproductive structures on the planet are zombie-esque in their malodorousness. Rafflesia arnoldii is a species of Indonesian rainforests with the largest flowers known to science. Individual flowers can be as wide as three feet across and weigh 15 pounds... and every bit of them smells like a rotting water buffalo.
Another species, the titan arum or corpse flower, has become famous in many circles for the size and stench of its flowering structure. The large floral shoot (or inflorescence) can be as tall as 10-12 feet (3.5 meters) and weigh as much as 175 pounds. This plant is impressively foul-smelling and tends to draw a crowd: More than 7,000 people visited a specimen at the University of Connecticut when it bloomed a few years ago.
Numerous other species are of a similar ilk. Some not only smell like dead meat, but look a lot like it -- with red, purple, and white markings that resemble muscle tissue -- and, occasionally, some even bear dense hairs that look surprisingly mammal-like. Sure, a flower may not look exactly like animal flesh, but the reproductive pay-off of fooling a few wayward insects into picking up or depositing pollen is worth the investment of getting close enough to pass for so much carrion.
Of course, the whole deal depends on there being actual decaying things in the world for insects to use successfully. Without real places for flies to lay eggs, for example, the flowers of terrible scent have nothing to aspire to. You can't mimic something that doesn't exist.
Or can you?
Maybe skunk cabbage, rafflesia, and the corpse flower are anticipating the future that TV tells us is right around corner. If we do end up with a planet crawling with zombies, the flies will have a field day.
So will all of those sapromyophilous flowers.
Perhaps it's been their plan all along.