A new scent is enough to spark the evolution of a new moth species — and it can start with just a single genetic mutation.
Since the 1970’s, scientists have known that European corn borer moths are split between two groups. Each has a different molecular configuration of ECB, a pheromone emitted by females to attract males. The different groups are biologically capable of interbreeding — in captivity, given no other choices, they do — but in the wild, they stick to their kind.
This sort of division is called reproductive isolation, and it’s an early step in the separation of one species into two. And while the importance of pheromonal differences to moths is understood, the underlying genetic mechanisms were not known.
In a paper published in the July 1 Nature, Max Planck Institute geneticists cross-bred captive representatives of the two corn-borer groups. By comparing the gene profiles of offspring to parents, they were able to trace the pheromonal differences back to changes in the DNA sequence of a single gene called pgFAR. Exactly why such small changes should make the corn borers so picky is a mystery, but they clearly do.
“This is the first functional characterization of a gene” that produces reproductive isolation in moths, wrote the researchers. Moreover, a scan of other insect genomes showed pgFAR to be present only in Lepidoptera, the insect order containing moths and butterflies. Mutations to pgFAR have helped “generate the great diversity of pheromones used in moths, permitting the coexistence of thousands of species,” they wrote.
The findings could help design synthetic pheromones for use in disrupting breeding in corn borers, which outside the world of evolutionary biology are a common farm pest. Of course, with speciation so easily stimulated, such schemes may well lead to the evolution of new species.
Image: Corn borers mating./Jean-Marc Lassance.
Citation: “Allelic variation in a fatty-acyl reductase gene causes divergence in moth sex pheromones.” By Jean-Marc Lassance, Astrid T. Groot, Marjorie A. Lienard, Binu Antony, Christin Borgwardt, Fredrik Andersson, Erik Hedenstrom, David G. Heckel & Christer Lofstedt. Nature, Vol. 466, No. 7302, July 1, 2010.