Attractive scent in insects as important as good looks: study

An attractive scent is just as important as good looks when it comes to choosing a mate – at least among stick insect populations, according to a new study.

It could explain why, when looks are deceiving, the insects are still able to show a preference for mates from the same species – a key to evolutionary success, according to the study by scientists at the University of Sheffield and Royal Holloway, University of London.

The findings, published in the journal Nature Ecology and Evolution, are part of an 18-year research programme, in which scientists examined stick insect populations in California to try to understand better what drives new species formation.

In evolutionary terms, the ability to avoid mixing genes with other species is important to preserve differences between species and evolve characteristics that are advantageous to survival. Natural selection plays a large part in this.

For example, if an insect population has developed an effective camouflage that prevents birds from eating them, a new population of non-camouflaged individuals moving into the area might not last long, and so would be only a minor threat to the gene pool.

The teams at Sheffield and Royal Holloway, studied more than 100 populations of stick insects, including 11 separate species, over nearly two decades, to try to find some answers to this evolutionary puzzle of how new species form.

"Species formation generally takes place over huge timescales and it's very difficult to observe directly – mainly we just get snapshots of what's happening at a particular moment in time," said Patrik Nosil from the Department of Animal and Plant Sciences at the University of Sheffield.