Flowers of asexually-reproducing plants (EvoWiki)

See the bottom of the article for updates reflecting responses to this page.

Clarifying the Argument
"Some flowering plants, like some dandelions (Taraxacum), reproduce parthenogenetically. However, dandelions and others continue to produce flowers, even though they do not need to attract pollinators in order to reproduce, making those flowers vestigial."

Let's examine the claim here:
 * 1) Dandelions reproduce asexually;
 * 2) Dandelions produce flowers, even though the flowers are not necessary for reproduction;
 * 3) Therefore, dandelion flowers are vestigial, meaning that the ancestors of dandelions used to reproduce sexually, but the species no longer does so.

The flower is not vestigial but indispensable
The first issue is, why do you argue that the dandelion flower is redundant? Perhaps you're unaware that the dandelion flower becomes the dandelion clock which propagates the seeds and the genus? Perhaps you've never noticed that the dandelion flower becomes the seeds which schoolchildren love to blow all over the schoolyard? Perhaps you'd never concluded that the genus could not survive without the flower?

So let's make one thing clear. The dandelion flower is not vestigial. It's indispensable.

Aesthetic engineering
But just for the sake of argument, let's assume you didn't make a mistake any third grader in the school-yard would correct you on when they blew the dandelion seeds all over the grass. Let's make-believe that the dandelion flower is not indispensable for reproduction. This takes us down a whole other line of thought.


 * 1) Why do you assume that the ancestors of dandelions used to reproduce sexually?  Can you identify which other flower was the sexually-reproducing ancestor of the dandelion?  If so, what was it?  If not, then why do you claim that there was one?
 * 2) Isn't the real reason you conclude that the flowers are vestigial because you can't grok the possibility that a trait might exist for a purely aesthetic purpose?  That you can't admit the possibility that flowers might exist not only because they are useful, but because they are beautiful?
 * 3) If indeed an organism exhibits traits which are not useful, but beautiful, wouldn't that be superoptimal rather than suboptimal?  Wouldn't it be evidence that things are the way they are not only because it allows them to reproduce, but because somebody wants them to be beautiful?
 * 4) And if we were to find a dandelion reproducing asexually but still producing colorful flowers for no apparent reason, might we not conclude that the flowers are not vestigial, but actually intentionally designed to be beautiful?
 * 5) And if we were to find an inordinate number of objects designed around aesthetic considerations, such as the Golden ratio, might we not reasonably conclude that they were designed not only to reproduce, but to be beautiful?
 * 6) Or how would you explain the fact that organisms such as the dandelion exhibit signs of aesthetic engineering without any identifiable survival value?  Ah yes, you'd call it "vestigial" without any evidence of a dandelion-ancestor that reproduced sexually but then lost that ability.  Very scientific of you;
 * 7) Which leaves us with our final question: Why in the world would dandelions lose the capacity for sexual reproduction, with its many advantages for survival and adaptivity?

Usefulness
And lest anybody make the hasty argument, "Dandelions!? Beautiful!?  They're a gardener's nightmare!" Consider: The leaves are more nutritious than anything you can buy. They're higher in beta-carotene than carrots. The iron and calcium content is phenomenal, greater than spinach. You also get vitamins B-1, B-2, B-5, B-6, B-12, C, E, P, and D, biotin, inositol, potassium, phosphorus, magnesium, and zinc by using a tasty, free vegetable that grows on virtually every lawn. The root contains the sugar inulin, plus many medicinal substances.

One other interesting fact about dandelions: they were imported into the Midwest of the United States from Europe in order to provide food for bees before the other flowers were out. The dandelions don't need the bees, but the bees sure need the dandelions.

First update
The following text was added to the evowiki article within hours of the time this article was posted on 12/29/2005.  "produce flowers with non-functional stamens and anthers,"

The stamen and anther in the dandelion are fully functional. The dandelion self-pollinates, meaning that the flower still produces pollen and still pollinates by the use of its stamen and anther -- it simply pollinates itself. Self-pollination holds some advantages over mere budding and cloning, because it allows for some degree of genetic variation in the population. 

Second update
The following text was changed on the evowiki article within minutes of the time this article posted the last update. 

"self-fertilizing ovaries, along with bright yellow petals that remain attractive to pollinators such as bees, making the opened dandelion flower redundant."

The opened flower is not redundant, the open flower produces the seeds. If the flower did not open, the seeds would not be produced, nor would they be exposed to the wind, allowing the wind to carry the seeds. The open flower remains extremely valuable for the reproduction of the dandelion.

Further, the ovaries are not redundant, but necessary for reproduction, so we're all wondering why you mentioned them there.

All you're really saying is the beauty of the dandelion is redundant. But as discussed above, beauty is only redundant if you deny that it was designed to be beautiful.

Third update
"Another example of an asexually-reproducing flower is the genus Myrmecodia, aka "Ant Plants," of Southeast Asia and Papau New Guinea. These epiphytic plants have swollen, hollow stems which house colonies of the carnivorous ant Iridomyrmex, and reap an enormous, multi-layered bounty, in that Myrmecodia benefits from protection against herbivores, feeds off of the ants' wastes, and receives extra carbon dioxide from the ants' exhalation. However, Iridomyrmex and other ants coat themselves with an antibiotic secretion called myrmicacin in order to protect themselves from fungal and bacterial disease outbreaks. Much to Myrmecodia's detriment, myrmicacin also kills pollen grains. In order to prevent their ant symbiotes from sterilizing them, the small, white flowers do not open, and the pollen grows directly from the stamen and into the style of the anther, and the seeds grow into clones of the parent."

The primary argument above remains valid. If a plant has beauty without function, one may reasonably conclude that it was designed to be beautiful. On the other hand, one may only conclude the flower is vestigial with evidence of an ancestor of the plant that used the flower for a different purpose. And even if one were to find one, it would still only be evidence of deevolution, because the plant has lost the ability to reproduce sexually.

Fourth update
"Flowering plants use flowers to attract pollinators such as bees. That way, the pollinators carry pollen from one flower to the next and make sexual reproduction possible. But some flowering plants, like the common dandelion (Taraxacum officinale), reproduce asexually. However, the dandelion continues to produce flowers with self-fertilizing ovaries, along with bright yellow petals that remain attractive to pollinators, making the opened dandelion flower redundant."

The statement, "Flowering plants use flowers to attract pollinators such as bees . " is false. Both flowers listed on the page are examples in which flowers do not use flowers to attract pollinators. But our author assumes, without evidence, that all flowers used to use their flowers to attract pollinators. Why does he assume this? That's certainly a broad claim with no evidence to support this. He assumes it, of course, because he cannot admit that flowers might be intended to be beautiful, rather than simply useful for reproduction. He is Manufacturing facts from a theory, one of the saddest logical fallacies of all.

Fifth update
"When one glances at the plant family Crassulaceae, one would get the impression that reproducing through seed is wholely redundant, as the vast majority of the members of this family can reproduce through the production of new plants via stem and or leaf fragments. The popular houseplant, the jade plant (Crassula ovata), easily demonstrates the family's clonal ability. The crassulids of the genus Kalanchoe, in particular, demonstrate a whole spectrum of regenerative ability, from species that will only produce clones through cuttings, to those species that spontaneously develop plantlets on the tips of their leaves.  Ironically, many species of Kalanchoe are monocarps, and die soon after blooming."

The author is apparently unaware that self-pollination is not redundant, but quite useful, because it allows variation among the descendants that mere cloning does not permit.

Related References

 * Flowers of asexually-reproducing plants EvoWiki