Chemical ecology: A look back and forward from pioneers in the field

During a workshop in Warren Hall April 14 as part of the Iscol Environmental Lecture Series, from left, Theodore Hullar, professor and director of the Cornell Center for the Environment, speaks with Iscol lecturers and Cornell professors Jerrold Meinwald and Thomas Eisner. Robert Barker/University Photography

By Roger Segelken

Chemical ecology, the result of a 40-year collaboration that produced many scientific breakthroughs in the field that wasn't even named when they began, has posed even more questions for the next generation of investigators, said Jerrold Meinwald and Thomas Eisner, keynote speakers April 13 in the Jill and Ken Iscol Distinguished Environmental Lecture series on campus.

The passing-of-the-torch talks in Statler Auditorium by Eisner and Meinwald, the Jacob Gould Schurman Professor of Chemical Ecology and the Goldwin Smith Professor of Chemistry and Chemical Biology, respectively, were bracketed by presentations from two younger scientists who have accepted the challenge, after learning their chemical-ecology essentials at Cornell. May R. Berenbaum, University of Illinois professor of insect entomology, opened the two-day series, which was presented by the Cornell Center for the Environment, April 13 with a discussion of phytochemicals that keep most -- but, significantly, not all -- insects from eating plants. And Ian T. Baldwin, director of the Max Plank Institute for Chemical Ecology, wrapped up the annual lectureship, following a brainstorming workshop among other chemical ecologists from Cornell and the Boyce Thompson Institute the afternoon of April 14, by highlighting the genetic basis of plants' resistance to insects.

Both Berenbaum and Baldwin earned their Ph.D.s at Cornell when the Eisner-Meinwald collaboration was growing a new science and an excited Eisner would periodically send a smidgen of unidentified goop, found oozing from an oddly acting plant or insect, across campus for Meinwald to analyze.

Berenbaum based her talk on her own latest, curious chemical of interest, the (almost) totally effective, plant-based insect repellents called furanocoumarins. That class of phytochemicals, she said, keeps parsnips safe from all nibbling bugs except one that has evolved its own countermeasures, and also gives celery-pickers itchy skin. The plant chemical, which is activated by ultraviolet light, got an anonymous young woman into the medical literature -- after a sunny poolside game of rolling limes between her thighs -- with the newly named malady, "Club Med Photodermatitis."

But Berenbaum, who is better known on Illinois' Urbana-Champaign campus for hosting the Insect Fear Film Festival of science-mangling movies, had to agree that chemical fact is stranger than fiction after hearing the elder scientists' recitation of their bizarre discoveries.

·There was the "femme fatale firefly," a chemically challenged lightning bug that knows the Morse Code-like signal of its own species and flashes back to attract a mate. But since neither she nor he can make the defensive chemical their species needs to deter predators, the femme fatale imitates the flickering signal of another firefly species that can. When a male of that chemically gifted species responds, she doesn't mate but instead eats him to get the defensive chemical for herself and her offspring.

·Or the millipede that scientists thought was making its own camphor because it reeked of mothballs, until the Eisner-Meinwald team proved the active chemical was, in fact, one that is rarely found in natural organisms -- but is essential for dynamite.

·And of course the bombardier beetle, described by Eisner as the flagship insect of chemical ecology, that posed a tactical puzzle: How can a bug spray boiling-hot, 100-degree-Celsius liquid without cooking itself? The answer, again, is clever chemistry. Two compounds, stored separately at the rear of the beetle, combine at the last split second for a chemical reaction that creates tremendous heat to scare off predators.

While recounting their impressive list of scientific accomplishments, Meinwald, 73, repeatedly commended the next generation of chemical-ecology problems to those with 40 years to spare. One such is the question of human pheromones, which Meinwald said have been hypothesized from behavioral studies but have yet to meet the tougher test of chemistry.

Eisner, who will be 71 in June, said he is frequently asked: How thoroughly has nature been explored, chemically? He said he answers "indirectly," by pointing out that millions of organisms on Earth have yet to be identified, much less explored in detail by science. "We are looking for a bacterium on Mars, while standing on thousands of unknown microorganisms beneath our feet," he said.

So much work remains to be done, Eisner said, addressing one of the practical applications of his basic science. Chemical ecology's adjunct, chemical prospecting, can draw attention to plant and animal genes responsible for making potentially useful compounds for mankind, and those genes can help engineers to make more of the material without depleting nature. "Biotechnology teaches us how to play with genes," he said, "but it doesn't tell us which genes are worth playing with."

Referring to legal contracts he brokered between nations with unexplored natural resources and pharmaceutical companies that want to do chemical prospecting, Eisner said that chemical ecology's "material goals are not pure, but they are important" if they lead to conservation of biodiversity.

More importantly, he said, "chemical ecology will flourish because it can help explain nature. Chemical bonds are the fundamental ones in nature," said the scientist who developed long-distance friendships with school children who saw his work depicted on television and wrote him letters. "Ultimately [chemical ecology] will endure," he said, flashing a photo of a curious child on the Statler Auditorium screen, "because it is interesting."