The process, thought to apply to any number of intimately interacting species, was articulated 34 years ago by Dr. Paul Ehrlich at Stanford University and Dr. Peter Raven at the Missouri Botanical Garden and explains a living world that seems to evolve to ever-greater diversity. It is particularly nice because, in recent years, the theory of co-evolution had fallen on hard times, in large part because of a study published in 1993 in Science by Dr. Conrad C. Labandeira, paleobiologist at the National Museum of Natural History at the Smithsonian Institution, and Dr. Jack Sepkoski, a paleobiologist at the University of Chicago. The two researchers found that in the fossil record, the numbers of insect families, which are large groups of many insect species, did not increase with the appearance of flowering plants, suggesting that insect diversity was not associated with the diversification of the plants they ate. The earlier study, he said, looked at insect families, while the current study looks at the numbers of insect species. Labandeira said that his continuing study of fossil species would probably corroborate the new findings.
Some questions remain about the species-rich beetles.
As Dr. May Berenbaum, evolutionary ecologist at the University of Illinois at Urbana-Champaign notes, it remains a mystery why beetles diversified so much more wildly than other insects or even mammals whose mainstay is also the shoots, roots, leaves, flowers or seeds of these plants. Perhaps the most surprising result was the discovery that while some beetles developed many new species that could eat the evolving new plant species, other beetles were remarkably conservative in their eating habits. At the base of the beetle family tree, Farrell found a number of ancient lineages of leaf beetles, snout beetles and long-horned beetles that still eat the primitive gymnosperms that they ate 200 million years old when dinosaurs ruled the earth. Farrell said these ancient associations are the oldest plant-insect antagonisms known. In Argentina, where beetles still eat Araucaria, an ancient lineage of gymnosperms, scientists have even turned up fossil Araucaria plants chewed up by ancestors of these beetles.