Man-Eaters of the Plant World

The adaptive advantages of sexual trickery

by Claire McKeever, guest writer; illustrations by Maleeka Marsden

The media thirsts for scandals, constantly sniffing out the latest scheming politician or adulterous celebrity. We have a fervid fascination with what such lewd acts represent—acts we would, of course, never dream of committing ourselves. From our earliest playground years, we are taught to play nice with our fellow human beings. We share snacks, we tell the truth, and we keep our promises. Yet the allure of an affair reveals that some fundamental element of our character opposes our ingrained moral constraints. From a biological vantage point, many of our social courtesies indeed contradict the driving forces of natural history. On one hand, we believe in “survival of the fittest,” but on the other, societal rules and norms undermine this conviction to uphold the sportsmanship of the game. Nature provides an array of cases to show that playing fair doesn’t always give you the greatest advantage.

Take the orchid, for example; here is a species  that doesn’t let concerns about courtesy hold it back. Fossil evidence indicates that the family Orchidiceae started blooming 84 million years ago, and phylogenetic structures suggest that orchid ancestors may have first bloomed as long as 100 million years ago. Several of these species outlived the dinosaurs during the mass extinction of natural life 65 million years ago, and survivors have proliferated today to include more than 22,000 species—four times as many species as mammals, and at least twice as many as birds. They boast a robust constitution as well, thriving in virtually all climates. Orchids reside above the Arctic Circle to the north, on Macquerie Island near Antarctica, and at every latitude in between. The sensuous curves of the orchid’s blossoms make them enchanting, elegant, exotic; one glance leaves no question as to why they have long symbolized delicate beauty, perfection, and refinement. They are the aristocrats of the plant world and they flourish with the glory accorded to their privileged class. Many tropical orchid species are epiphytes, or “air plants,” that entwine around host species and recline high in the canopy of rainforests, close to sunlight and away from the bustle of the forest floor. Their wily lithophyte (“rock plant”) relatives take root on the surface of rock where lesser plants fail to gain a foothold.

Taken out of their natural habitat, however, orchids are immensely fragile and require constant tending. To what, then, can we attribute the uncontested domination of the orchid among flowering plants? In truth, they have ascended through the ranks using brazen trickery. Let’s take a look at the Five Tongue Orchid species (genus Ophrys) native to Oceania. In unique ways, each organism imitates the female Orchid Dupe wasp (Lissopimpla excelsa), thus beguiling the male wasp into attempting to mate with it. In the process, the wasp picks up pollen from the flower and carries it to its next deceptor. Tongue Orchid variations appear different to the human eye, but to a wasp their hues are indistinguishable from those of their female cohorts. Some flowers lay claim to parts that feel like female wasps, such as faux versions of the “love handles” that the male wasp holds onto during copulation. Several also emit a scent to mimic female wasp pheromones. Other orchid species entice pollinators with sweet scents or brightly colored flowers that create the ruse of nonexistent nectar.

All such adaptations give orchids a creative biological advantage. The plants are hermaphroditic, possessing both male and female reproductive structures. Without reliable pollinators, they risk self-pollinating, which results in a dramatic decrease in genetic variation and poses a serious threat to the species’ ability to adapt to environmental changes. When pollinators find that their lust is unrequited, they quickly lose interest. By playing hard-to-get, the orchid ensures that the pollinator will leave before it has time to re-deposit pollen onto the flower itself. Orchids take further advantage of the blind throes of lust into which the insects plunge themselves—because wasps will travel farther to mate than to forage, orchids expand their feasible habitat by fooling the naive insects into following them on a passionate pursuit. The poor wasps gain very little from this arrangement; but in the grand scheme of the natural world, it is better to have pollinated and lost than to have never pollinated at all.

Anne Gaskett, a graduate student and researcher at Macquarie University in Sydney, has studied these seductress orchid species extensively. In her research, she has found that “over generations the insects learn to avoid having sex with orchids, and this means only the most persuasive orchids reproduce, which drives the acceleration of orchid subterfuge.” Not only are the orchids unfaithful lovers; they are also masterful deceptors who benefit by continuously finding new ways to dupe their hapless pollinators. Suffice it to say that the plant world would have no qualms with Tiger Woods or Bill Clinton.

What right do we have to impose a system of moral balance on an unforgiving and unpredictable natural world? Human heroes are lauded for their sincerity and honesty, but such merits convey no advantage without the cushion of a dutifully enforced code of virtues. Perhaps Thomas Hobbes’s “Leviathan” government, by constraining our bestial impulses, in fact constructs a society that stunts the natural progression of our species. With impending nuclear proliferation, an increasing crime rate, and an unstable global economy, it might prove to be the orchids among us who ultimately reign victorious. For their disingenuousness and guile, Mother Nature rewards Orchidiceae with unprecedented evolutionary success among the flowering plants. And a 100-million-year-long family history is a hard track record to dispute.

Man-Eaters of the Plant World

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