Study Confirms Classic Theory on the Origins of Biodiversity

A team of researchers at Cornell University lead by Anurag Agrawal have conducted a series of studies on applying phylogenetic approaches to study the history of life and the co-evolution of plants and insects and how their interactions lead to greater diversification of both groups. One of the studies featured in the series and published in the Proceedings of the National Academy of Sciences is on how milkweeds diversify to follow the 1964 theory of adaptive radiation by scientists Paul Ehrlich and Peter Raven. It is a process when species rapidly multiply and diversify for a time as they colonize new resources and then level off.

The report said that, "As milkweeds developed prickly, hairy leaves, highly toxic chemicals (cardenolides) and gooey white latex that gums up a predator's mouth, the monarch butterfly caterpillars evolved to become immune to the toxins, learned to cut the veins in the leaves to drain the latex before they ate them and shaved off leaf hairs with adopted mouth." However, instead of the milkweeds continuing to adapt and develop more defenses against the caterpillars, the plant has increased its ability to grow leaves back quickly – a phenomenon that slightly deviates from the principle.

With this discovery the team is aiming for more studies on plant/ insect interaction. "It's still a mystery why there are 300 times more herbivorous insects than bird species, but now we are able to implicate traits of both plants and insects that have given rise to so many species," said Agrawal. "The interaction between plants and insects has been part of their adaptive radiation."

See the report at:http://www.news.cornell.edu/stories/Sept09/AgrawalMilkweed.html