Milkweed’s Evolutionary Approach To Caterpillars: Counter Appetite With Fast Repair

July 24, 2008

The adage that your enemies know your weaknesses best is especially true in the case of plants and predators that have co-evolved: As the predators evolve new strategies for attack, plants counter with their own unique defenses.

Milkweed is the latest example of this response, according to Cornell research suggesting that plant may be shifting away from elaborate defenses against specialized caterpillars toward a more energy-efficient approach. Genetic analysis reveals an evolutionary trend for milkweed plants away from resisting predators to putting more effort into repairing themselves faster than caterpillars — particularly the monarch butterfly caterpillar — can eat them.

"An important question with co-evolution is where does it end?" said Anurag Agrawal, Cornell associate professor of ecology and evolutionary biology and lead author of a paper in the current issue of the Proceedings of the National Academy of Sciences. "One answer is when it becomes too costly. Some plants seem to have shifted away from resisting herbivory [plant eating] and have taken that same energy and used it to repair themselves."

A monarch butterfly caterpillar gets ready to devour a milkweed leaf. Before feeding, the caterpillar disarms the plant’s natural defense system by cutting the milkweed’s veins that deliver a toxic and sticky latex. (Credit: Anurag Agrawal)

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Posted in Nature, Science and Technology