Orchid Deception: Is It Evolution?
Orchids comprise the most exotic and diverse group of flowering plants. Some 30,000 species strong, this group contains members with unusual sex organs. Some have organs that look and smell like the female of the insect species that pollinate them. They seduce the males without giving them a reward of nectar for their stopover. How could such a strategy of deceptive seduction evolve?
Heidi Ledford explored this question in Nature last week.1 About a third of orchids seduce pollinators without giving them nectar. The orchids that deliver nectar typically have better reproductive success, at least in terms of numbers of offspring. Darwin thought that the insect pollinators would eventually learn the trick and avoid the flowers, driving them extinct. Ledford explained how evolutionary theorists believe, however, that “dishonesty gives them the evolutionary edge.”
This might work, for instance, by reducing inbreeding. A pollen-dusted but disgusted visitor may fly to more distant plants, where they are less likely to visit the orchid’s kinfolk. An evolutionary biologist explained, “To be deceptive means that the orchids have less sex, but the sex is better because it’s not with a close relative.” From the insect’s point of view, though, how do biologists answer Darwin’s enigma? Why don’t male bees catch onto the trick? Some suggest that young males are profligate, not picky, among the scarce females. One researcher puts himself into the bee brain, saying, “Hey, I will go for anything that looks like a female because I can’t afford not to.”
Does this explanation hold up? Does it explain the origin of the elaborate reproductive organs of the flowers, and their amazing ability to mimic the pheromones of female insects? Further digging in the article shows problems. Researchers mentioned in the article are looking for evidence of “sympatric speciation,” a controversial idea that has lacked firm evidence despite decades of investigation.2 Evidence that this has actually occurred in the case of orchids is only tentative at best.
Additionally, today’s oddball orchids may represent degenerates of more complex ancestors. Ledford comments that “plants produce hundreds of volatile compounds to repel predators and microbes”; one of the pheromone mimics, in fact, a complex chemical concoction, consists of “14 different compounds that are also common components of the waxy cuticle that protects the surface of many plants.” Elaborating on how this might have happened, she said,
They showed that the same combination of compounds is present in the volatile sex pheromone that a female bee uses to attract a mate, and that a blend of these chemicals could make bees mate with dummy flowers. The finding also revealed how sexual deception could have evolved in this species by gradual modification of systems the plant was already using to make its own compounds. Each tweak in the ratio of compounds that increased pollinator visitation would have given the orchid a reproductive advantage.
Yet it seems hardly a law of nature that some species would opt for deception, luring pollinators without a reward, while others would stick with the standard strategy of rewarding visitors with nectar. The former get less sex with better quality while the latter get more sex (and more offspring) yet with risk of inbreeding. Plausible as this sounds, the same theory is being used to explain opposite strategies among very similar plants. This seems hardly a deterministic explanation.
The most promising evidence for the evolutionary view in Ledford’s article was that a certain Australian species appears to have invented its pollinator’s pheromone from scratch:
The team found evidence to back this idea [that plants attract pollinators by adjusting their chemical bouquet] in the orchid blooms of Australia. They repeated the experiment [matching plant compounds with pollinator odor receptors] on the orchid Chiloglottis trapeziformis, which tricks the male thynnine wasp (Neozeleboria cryptoides). Analysis of C. trapeziformis scent revealed a surprise – rather than adapting existing mechanisms, the orchid was producing an entirely different chemical compound they named chiloglottone, which is also a pheromone made by female wasps. They also found that another Ophrys species, O. speculum, concocts a different wasp pheromone by developing several novel compounds. In this case, the orchid mimic worked so well that, when offered a choice between a female or an orchid, male wasps courted the orchid.
The article did not elaborate, however, on how the botanists knew that the ability to produce these compounds was not already present in the ancestor. Some species produce the chiloglottone, while others do not. To call a compound “novel” would require knowledge of the genetic history of today’s species. It would require knowing whether the haves evolved from the have-nots rather than vice versa.
Nevertheless, the plants and their pollinators show remarkable specificity today. Insect pollinators such as wasps and bees are often picky about the flowers they visit, and the flowers often show exotic adaptations to succeed in attracting the right insects. The article left the question of sympatric speciation unresolved. Ledford did not address, furthermore, the larger questions of how these flowers and insects arose in the first place.
1Heidi Ledford, “News Feature: Plant biology: The flower of seduction,” Nature 445, 816-817 (22 February 2007) | doi:10.1038/445816a. 2Sympatric speciation (as opposed to allopatric speciation) suggests that species can split into two without members becoming geographically isolated. See 01/15/2003.
Nothing in this article contradicts the view that today’s highly-specialized exotic plants and their pollinators represent degenerations of original complex ancestors. By degenerations, we mean that they contain less genetic information than the parents. If the parents already possessed the genetic information and machinery to produce hundreds of volatile compounds, it is plausible to presume that they eventually lost the information that was not needed for survival in specialized environments. This is not evolution in the macroevolutionary sense – the sense needed for propping up the Charlie idol.
Think of a well-equipped soldier landing in Iraq with all-purpose gear and deciding he can shuck his snow parka. He is now better adapted to his new desert environment. Does that mean he is more highly evolved? Of course not. As with the case of blind cave fish (02/16/2007), natural selection (a conservative process) eliminates the excess baggage and only retains and exaggerates what aids survival. None of this requires new genetic information. The Darwinians cannot make a case here that orchids and wasps evolved from bacteria.
That being said, this article shows that the study of microevolutionary adaptations is a legitimate area for research. Learning more about how orchids and bees have become adapted to their unique ecosystems can help explore the processes of horizontal change over time. It’s interesting, also, that even the evolutionary biologists themselves admitted that these adaptations could occur rapidly. One researcher was quoted saying, “We think that speciation can occur fairly quickly in that system. The plants need only to change their odour bouquet to attract a new pollinator.” These horizontal sorting-out adaptations do not require millions of years.
Keep in mind, furthermore, that the concept of “species” is artificial and controversial. The simplistic high-school definition that a species is a group of organisms able to produce fertile offspring has problems when investigated in detail; what about asexual organisms? What about fossils? Philosophers debate over to what extent the word species represents something real in nature instead of an artificial construct we impose on nature. And for those who think the scientific-sounding word species is more intellectual than the Genesis word kind, we remind them that species comes from the Latin word for kind. We add that the father of taxonomy, Carolus Linnaeus, was motivated to classify living things in order to explore the limits of the Genesis “kinds”. As a footnote, his method of classifying plants was by their reproductive organs. Not all botanists have agreed with his criteria for classifying species; nevertheless, Linnaeus considered the pistils and stamens of flowers exquisitely designed structures for both function and beauty.
Orchids surely are among the most beautiful, prosperous, diverse life forms adorning our world. It’s no wonder they are flowers of choice for corsages on that special date. Yes, they have diversified into a splendid array of fascinating varieties. Calling this evolution, however, risks confusing the larger issues with Darwinian materialism (see 02/25/2007 commentary) that reduces sex to selfish strategizing and nihilism (05/01/2002, 02/14/2007). Evolutionists are in no position to claim they understand the origin of sex (e.g., 05/16/2004, 05/12/2004) in all its bewildering complexity and diverse manifestations. If materialism cannot deal with the origin of sex, much less can it address questions of human mores and aesthetics. Why we find orchids beautiful, and why we should be honest and faithful to our soulmates, are not questions for Darwin.
It’s forever important to reason properly and avoid logical pitfalls. Confusing microevolutionary adaptive sorting with macroevolutionary innovation is the fallacy of equivocation. Envisioning plants strategizing for reproductive success, and being capable of dishonesty and deception, is the fallacy of personification. And taking observable evidence from the present and stretching it to absurd lengths into the unobservable past is the fallacy of extrapolation. Be reasonable (adj., not exceeding the limit prescribed by reason; not excessive). After that requirement is met, reward your soul: take time to smell the orchids.