People seem to be obsessed by pheromones; even though they don’t influence our behaviour much, they still dream of some magic bullet that would offer them a lot of sex. In other mammals and many insects, this might be the case. Moth pheromones guide males towards the females, even on the darkest of nights.

Pheromone recognition systems appear very specific, and they are thought to be important in the evolution of mating barriers and in the emergence of new species. When conspecific males and females recognize each other by their common highly specific ‘language’, mutants employing slightly different signals are likely to have lower fitness. They most probably die without breeding, or, in some rare cases, they may find and mate with a mutant partner, generating a new line that would eventually turn into a new species. These new individuals would inherit the mutant communication system and could spread it, forming a new species.

The European corn borer (Ostrinia nubilalis) is a moth species with two types of females and two corresponding types of males: one type emits the “E” pheromone and the other, the “Z” pheromone. Hybrids between the two types are perfectly viable, but the two types very rarely cross in nature and apparently this confirms the pheromones’ theory of difference. However, a team from the Institut National de la Recherche Agronomique, from the Centre National de la Recherche Scientifique and from the University of Toulouse revealed that while pheromones are probably employed for meeting, they are of no use for mating per se.

When the team made crosses and backcrosses between the moth’s two pheromone types, they obtained individuals having the same pheromone type but genetically different from the ‘pure’ races, and also individuals with a very similar genetic background to ‘pure’ races, but employing different pheromones.

The former should have mated with the pure-race individuals emitting the same pheromones, but they didn’t. The latter should have a biased mating success with pure-race individuals, but this did not occur. It appeared that genetic similarity counted more rather than pheromone type. Thus, pheromones seem to be not as important in speciation as previously thought, at least in moths, because other recognition systems interfere as strong mating barriers.

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Posted by Jonathan in Biochemistry, Biology

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