Thursday, February 5, 2015

Evolution of Herbivorous Insects



Researchers at the University of Arizona examined how evolution has affected the transition of non-plant diet insects to herbivores. This is an interesting topic to geneticists because herbivorous insect species make up half of all known insect species, but only one-third evolved from a non-plant diet. Benjamin Goldman-Huertas, lead author of the paper, explained how the transition to herbivory happened infrequently, but when it did, led to intense speciation. The reason for this infrequent switch is due to plants' defense system of tough outer skin and indigestible or toxic tissues. This explains why most plant-eating insects are parasites which use the plant they feed on to lay their eggs and leave their larvae. In their study, they used the Drosophila melanogaster, fruit fly, and it's close relative fly species the Scaptomyza flava to test the hypothesis that this transition needed drastic changes in behavior, which then required remodeling of the genetic and neurological processes of those behaviors. The Scaptomyza flava do not waste their time flying around rotting fruit like fruit flies; instead females seek out healthy plants, drink the plant juice, and then lay their eggs which then, as larvae, eat their way through the leaves leaving and possibly killing the plant.

Goldman-Huertas worked with John Hildebrand, a Regents' Professor in the UA's Department of Neuroscience, to measure electrical responses in the insects' antennae generated by olfactory receptors when the insects were presented with different scents. The smell of yeast, which grows on rotting fruit, is a huge attractant to Drosophila melanogaster, but left the Scaptomyza flava without a response. Conversely, only the Scaptomyza flava responded to the scent of freshly cut grass. They found a group of olfactory receptor genes that had undergone a disproportionate amount of sequence change suggesting Darwinian evolution has changed the function of these genes.

Overall, I found this article intriguing due to the work with the Drosophila melanogaster which is the species of fly we are currently using in lab. Also, it is interesting to note how, through evolution, the function of individual genes may change. The importance of this is highlighted in the end of the article as well, since it explains how gaining of this knowledge could help to stop the negative impacts of the Scaptomyza flava on canola in Europe and mustard plants in New Zealand. Furthermore, this could go on to explain how and why the Anopheles mosquitoes that spread malaria started feeding on humans and could lead to possible methods of increased prevention.



Original Article: http://www.sciencedaily.com/releases/2015/01/150129170402.htm

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