Milkweed evolves 'mind-blowing' tactic to fight monarchs

Milkweed has found a new strategy in its epic evolutionary battle with monarch butterflies: upgrading its toxins to outmaneuver the monarch's resistance. In a new study, published in the Proceedings of the National Academy of Sciences, researchers find that adding a small structural element containing nitrogen and sulfur to milkweed's toxins circumvents monarchs' ability to block them. The research sheds light on an underappreciated evolutionary tactic for plants: that not only can they increase their levels of toxicity, they can also structurally innovate to create new classes or subclasses of toxins.