A fascinating study was published last week in Current Biology about the relationship between the hawkmoth and the Coyote Tobacco plant, Nicotiana attenuata. N. attenuata is wild flowering plant found in the west, related but not the same as the cigarette tobacco plant grown in the south. (You may recognize it as a relative of the Nictiana plant that is a favorite perennial in New England gardens). The plant has developed - as many flowering plants have - a symbiotic relationship with its pollinator, the Hawkmoth. The moth picks up and disperses the plants pollen. The the benefit to the moth is that it frequently lays its eggs on the plant's leaves. When the eggs hatch, its larvae (the caterpillars) have their first meal - the plant itself.
This is obviously not a mutually beneficial relationship. Too many caterpillars and the tobacco plant population would begin to drop, and possibly disappear. The plant faces a choice: adapt or die.
Scientists has recently observed a startling adaptation taking place. The plant normally flowers in the evening hours during Hawkmoth high flight times. Recently, however, the tobacco plant has begun to flower during the morning, attracting a new and different pollinator: a hummingbird that has no interest in devouring its provider of nectar.
This is evolution at work. The plant has a choice in a figurative sense. It doesn't have a working brain capable of strategizing a plan for its own survival. There is something more primitive at work. Something elegant in its simplicity, and powerful in its determination: natural selection.
Natural selection, one of Darwin's main ideas in his theory of evolution is commonly thought of as "survival of the fittest". It refers to the fact that there is a great deal of variation within a population or organisms, in this case the tobacco plants. Most of the plants flowered at night and had a higher likelihood of being eaten by Hawkmoth larvae. A few plants, flowered earlier in the day. The earlier flowering plants survived, thrived, and passed their genetic code on to the subsequent generation of plants. They're the ones who had higher survival rates. The balance shifted between night flowering plants and morning flowering plants shifted towards to morning plants.
Interestingly though, the night flowering plants remain. Scientists hypothesize that the moths, which fly over a much larger territory, are superior pollinator and capable of spreading the plant's pollen to plants further away than the hummingbirds are able to.
Regardless - more and more of the tobacco plants began to flower in the early morning hours. This adaptation gave the population of tobacco plants the opportunity to recover and stablilize, ultimately strengthening this new trait that aids their survival. The species has changed. It has adapted to thwart a negative force in its environment.
It has evolved.
8 comments:
dear mr.e:
I find it amazing that the flowers are able to change their habits, even when they don't have a brain that is able to strategize. It seems so poetic in a way, that this beautiful flower changes its course in life, just like we do. I think I might one day refer to this action in my writing one day. Reading this article made me raise the question, if the Hawkmoth isn't pollunating the tobacco plant as often anymore then what as a result of that, is changing too?
~Kayce Mae
Well, I came on now partially to respond to a new post, if there was one up, but I guess I'll just respond to this one:
I think it is really cool that the plant 'chose' the pollenator that wouldn't devour it's leaves when it was young, but I wonder; there are still tobacco plants that flower at night, and the moths can fly far to reach them; maybe what is happening here is species diversion, not just change?
Peter
I find it not only amazing but impressive that a plant can evolve and change into a morning-flowering plant when it is beginning to show signs of extinction. And dispite not having a brain, it shows that the plant almost realized that it was on the path of destruction and that it needed to adapt in order to survive.
- Maya
There's something I don't quite understand about this: a species takes on a new characteristic through evolution if it is advantageous to its spread and reproduction. While it does make sense that not being destroyed by caterpillar=longer life=more time to reproduce, a plant must pollinate in order to spread its genes. If the new plants are served by a worse pollenator then before, how is this change spreading so rapidly? Does the longer lifespan balance out the less effecient pollination, or even outweigh it?
by the way...
WOW
than* before
sorry for the billions of comments but i had to add this:
i didn't consider the dayflowering plants only diversifying from the nightflowering plants instead of replacing them, as peter said. if they can cooexist, than that basically answers my question.
These tabacco plants are simply one example of the many thousands of Darwin's theory of "Survival of the fittest." Darwin's theory explains why there are so many varieties of organisms in the world. When a change in an organism's envieonment threatens its ability to survive, the organisms that have mutations that help them to survive live and pass on their DNA to their offspring, creating a new variety of that organism that is better adapted to their new environment. This article makes me wonder, along with Kayce, what are the moths doing to adapt now their their food supply is diminished?
Lydia K.
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