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Four orders of insects deal with toxic plants the same way


From “Same Adaptations Evolve Across Different Insects” (Science Daily, July 24, 2012), we learn,

A study published online July 23 in the Proceedings of the National Academy of Sciences finds that in the case of insects that developed resistance to a powerful plant toxin, the same adaptations have occurred independently, in separate species in different places and times.

The paper examines 18 insect species across four orders — beetles, butterflies and moths, flies, and true bugs — that all feed on plants containing powerful toxins called cardenolides.

“This is truly a remarkable level of evolutionary repeatability and suggests that evolving resistance to the plant toxin had very few effective options,” said Agrawal.

The standard gene for the sodium pump is essentially the same in all insects, and even mammals carry the gene in a relatively unmodified form. The sodium pump thus originated from a common ancestor hundreds of millions of years ago and is central to the functioning of most animals. Out of that background, insects from different orders over the last 300 million years specialized on plants with cardenolides and evolved resistance independently, and in numerous cases, through exactly the same gene change.

Here’s the journal reference:

S. Dobler, S. Dalla, V. Wagschal, A. A. Agrawal. Community-wide convergent evolution in insect adaptation to toxic cardenolides by substitutions in the Na,K-ATPase. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1202111109

We usually don’t provide the reference because you can get it from the linked story. What’s interesting is that the story doesn’t once use the term “convergent evolution” but the paper does.

Note: The photo is of a Monarch butterfly caterpillar. (Credit: Ellen Woods)


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