Dr. Florian Schiestl from the University of Zurich found that within the arum family there has been a one way evolutionary mimicking of scents that attract pollinators. Specifically in this case, arum plants secrete scent chemicals that attract scarab beetles to pollinate them. In many such plant-insect interactions the ordinary hypothesis is that these interactions develop through coevolution due to the mutualism involved. The concept is fairly straightforward: the insect derives benefit from the plant via nutrients or other resources, and the plant benefits from the service of protection or spreading the species' seeds or pollen. This interaction benefits both species and they adapt to each other to maximize benefit gained, resulting in coevolutionary development.
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| Member of the arum family (Araceae). Image Source: Wikipedia |
Dr. Schiestl found that within the scarab beetle known to pollinate arum plants there were many of the chemical signals found in the plants. Finding that they were the same scent compounds used to attract the scarabs, he and his colleagues used phylogenetic reconstruction and searched for the evolutionary origin of these compounds. It was discovered that the ancestors to the modern scarab beetles had been using these same scent chemicals since the Jurassic period, and also that these ancestral beetles did not pollinate the arum plants. From this, he concluded that the arum plants themselves simply mimicked the scarab scents and evolved to fit this niche by taking advantage of the scarabs, who have not adapted to the plants at all.
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| Rainbow Scarab Beetle. Image Source: http://www.projectnoah.org/spottings/7935873/fullscreen |
These findings are remarkable and contradict the current prevailing belief that coevolution is the major factor that induces and shapes mutualistic relationships. Dr. Schiestl noted that coevolution "might well be less common than we thought," and this discovery warrants further research into the evolutionary development of mutualisms.
Primary Literature Source: Florian P. Schiestl, and Stefan Dötterl. The Evolution of Floral Scent and Olfactory Preferences in Pollinators: Coevolution or Pre-Existing Bias? Evolution. International Journal of Organic Evolution. March 12, 2012. doi: 10.1111/j.1558-5646.20
Source link: http://www.mediadesk.uzh.ch/articles/2012/pflanzen-imitierten-duft-von-bestaeubenden-kaefern_en.html
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Fascinating. I am curious as to what sort of selection pressure led to the development of a scent like that of the scarab beetle rather than another potential pollinator.
ReplyDeleteThis is a very interesting finding indeed. I think coevolution theory mainly pertains to relationships that have been very very old. This may be an example of a relationship that has not disrupted the scarab's lifecycle enough to induce evolutionary change on their part. It's very likely that this relationship is still very young, evolutionarily speaking.
ReplyDelete-Tom Xia
This is pretty cool. It seems that there are many plants which "trick" insects into coming to pollinate. We learned in Insect Bio last semester that there is a plant that mimics a certain wasp's female body shape, attracting male to mate with it and thus pick up and spread its pollen to other flowers.
ReplyDelete-Jesse Passman
Im curious how these findings differ evolutionarily from examples like this one that you mention, Jesse. Since there are already several relationships where, as you say, plants trick insects with colors or fragrances into pollinating them, I wonder what is unique about the relationship between scarab beetles and arum plants that makes this study so surprising.
DeleteIn insect bio last semester we learned about several other cases of biased relationships that seemed to favor one organism over another. However, many of these relationships had underlying mechanisms to maintain the interaction, such as a shift in favor of a certain sex ratio. As Tom mentioned, I'd also be interested in seeing how this relationship will play out in the future; the scarab beetle will almost certainly have to evolve an adaptation to the arum species' mimicry sooner or later, as it will contribute to increased reproductive failure in the scarab beetles.
ReplyDeleteI dont understand why you write "contradict the current prevailing belief" as its obvious that this case isn't a mutualism but commensalism, no? As for ophrys orchids, the insect is fooled but its isnt a classic case with angiosperms.
ReplyDeleteI wonder though why those beetle chemicals havent changed though, as it seems that any variation would be benefical. Maybe the arum selection pressure is just close to zero.