The Beauty and The Beast

Mediterranean orchid photo by A. Scrugli, in Biology LettersOrchid flowers are amazing. Science journalist and top blogger Carl Zimmer recently wrote a blog on orchids, “Orchid Hacks,” commenting on a paper by Florian Schistl in the Journal of Evolutionary Biology that showed how orchids “hack” into the mate-recognition systems of male wasps. However, there is more than one way to “hack” a bug.

The orchid flowers that Zimmer discussed mimic the appearence of wasps, but exaggerate the physical features that male wasps key on. The deceptive flowers also release pheromones that mimic the female wasp pheromones, and once the flower is fertilized, the orchids mimic the chemical produced by fertilized wasp eggs, repelling male wasps. Darwin would not have been surprised, for he wrote a book, now freely online, which was all about the complex machinelike contrivances of orchid flowers, and how they could all be derived by coopting the parts of simpler ancestral flowers. It was a direct rebuttal of Paleyian thinking, unfortunately completely missed in the oh-so-careful literature searches of Behe and other ID advocates, and it goes unmentioned in their attempts to resurrect the Design argument from biological complexity. Orchids, and Darwin’s book on orchids, also played a key role in Stephen Jay Gould’s essay, “The Panda’s Thumb”, which we have named this blog after. For more on the role that beautiful orchids have played in the design-vs-natural selection debate, please see my EvoWiki page on orchids.

Dead-horse arum, Peter Boyce/NatureNot all examples of quirky evolution and jury-rigging are beautiful, however. Another famous case of flowers “hacking” the brains of insects involves an entirely different strategy. As reported in the staid academic journal Functional Ecology a few months ago:

In central Corsica, Helicodiceros muscivorus (Schott ex. K. Koch) produces a protogynous inflorescence that resembles the anal area of a dead mammal and produces a foetid scent during the few hours after sunrise.

The common name of this lovely flower is the dead-horse arum. You get one guess as to what it smells like. I’ll leave it up to the reader to determine if the flower (left) really looks “like the south end of a horse that died going north,” as botanist Roger Seymour put it, but any way you shake it, the arum’s adaptations are just as amazing as any orchids. The dead-horse arum produces chemicals “strikingly similar” to a those emitted by a rotting carcass. As if the looks and the smell weren’t enough, the flower generates its own heat to help disperse the smell. Apparently, carrion-eating blowflies can’t tell the difference between food and flower and are attracted to the flower like, well, like flies to meat. When the blowflies enter the flower, slanted spines prevent exit, and the flies are trapped overnight, spreading their pollen to the mature female florets inside the flower. The next day, the male florets mature, the flies pick up more pollen, the spines wither, and the flies are released to spread their pollen to other nefarious arums. As botanist Bill Hansson puts it, “The flower has the perfect system.” Undoubtedly he has anosmia.