Insect sex

	European corn borers

Insects can evolve new sex pheromone systems in a single leap rather than the more sluggish step by step process of evolution. The findings will probably be no great shakes to modern farmers using pheromone traps at least for the next few millennia, but the research does reveal just how fast and effective evolution can be.

Wendell Roelofs and colleagues at Cornell University in Geneva, New York, have unlocked the evolutionary secret as to how insects evolve into new species. The team was investigating ways of preventing European corn borers (Ostrinia nubilalis) from mating, multiplying, and devastating crops. They uncovered a previously undetected gene, the delta-14, that can regulate the attractant chemicals produced in the sex-pheromone glands of the female borer. It seems that this gene can be switched on quickly and change the fingerprint of pheromones the females use to attract a mate.

Wendell Roelofs

According to Roelofs and his colleagues, insects can evolve new pheromone systems in leaps rather than in minute stages. "This is one way that insects become new species," explains Roelofs, working with Alejandro Rooney of Mississippi State University. Roelofs points out that female insects attract males with specialized pheromones, which he compares to radio frequencies. At major events with thousands of people, for instance, police might communicate on channel one, emergency medical personnel on channel two, and administrators on channel three. "With male and female borers, it's the same thing," he claims. "Certain species communicate on channel one, others on channel two, others on channel three. But, when a female has a mutated [switched on] delta-14 gene, it changes her channel from three to five." Only one in 200 males will be able to respond to her new channel selection and mate with her. Eventually, the pheromone communication system will stabilize and essentially this new population becomes isolated from the parent species, a new species has evolved.

	European corn borers

"We have shown a mechanism for how pheromone blends could have evolved in the past," Roelofs told Reactive Reports, "Although we suggest that it might be possible to change to a new blend, I would not want to give the impression that this is something that can be done easily since it happened once with the corn borers a million years ago."

Farmers and horticulturalists have used pheromones to trap unwitting pest species for twenty years. Indeed, agricultural researchers have identified pheromones in over 1,000 species of insects and have exploited chemical communication to lure pest males into deadly traps or to otherwise disrupt the mating process.

Roelofs and Rooney's results suggest that insect populations might have the ability to circumvent the pheromones on which such traps are based. "Based on the difficulty of generating even small changes in pheromone blends in the lab, we thought that such resistance could not develop because natural pressure would prevent the species from gradually shifting to a different blend," explains Roelofs. The presence of this kind of gene, capable of sudden activation, might provide a mechanism for resistance to occur. Roelofs, however, is cautious of scaring farmers about devastated crops, "I would not want to suggest that the use of pheromones for insect control is in trouble because this could happen again. It is really a long stretch to think it would happen quickly in a field. Again, the real interesting thing is that it did happen in the past to form the new species, Asian corn borer."

DOI: 10.1073/pnas.152445399^*

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