Evolution in a toxic world

How life responds to chemical threats

Convergent at the molecular level – again

Monarch butterfly larvae on a plains milkweed.Earlier I highlighted convergent molecular evolution as demonstrated through research on tetrodotoxin resistance. Now it’s resistance to a common plant toxicant – the cardenolides produced by foxgloves, milkweeds and the African Stropanthus, a source of poison for arrows.  A new study by Susanne Dobler and colleagues demonstrates that over a dozen species spanning four different insect orders have all come about their resistance to cardenolides through the alteration of a common amino acid.  Noting that at least one similar case of convergent molecular evolution has occurred in contemporary time (in response to cyclodiene pesticides) the authors write, “The extent of convergence in molecular evolution thus does not depend on the type of selection or the available time frame. Rather, the likely soft selection caused by prolonged coevolutionary interaction between cardenolide-containing plants and herbivores has resulted in similar molecular convergence as the intense selection by some, but not all pesticides.”

For more see: “Community-wide convergent evolution in insect adapation…” PNAS, July 23, 2012. And additional post, Evolution Over and Over and Over again.


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