The trick behind magic traits revealed!

In a recent paper in Ecology Letters, Sergey Gavrilets and I revealed the trick behind magic traits: they can evolve!

Magic traits have been visited already in this blog, so I will only briefly introduce them here. Essentially, they are traits that are involved in both divergent selection and mate choice. Their involvement in mate choice can help a population to diverge into separate, reproductively isolated populations in response to divergent selection, and so they can greatly facilitate the process of ecological speciation. Initially it was thought that magic traits should be rare, and for this reason, models using them were considered not to be general. However, a study found that, surprisingly, they are not rare after all. We tried to find out why.

The book where magic traits were defined

We built a large-scale individual-based model of ecological speciation. In our model, individuals can be viewed as an assemblage of many traits. Each trait can be used for discrimination during courtship. These traits can be related to morphology, color, behavior, etc., but they all fall into two categories: under divergent natural selection or neutral. Initially, females choose their mate randomly; subsequently, they can evolve a preference for any trait or combination of traits. We found that females evolve almost exclusively preferences for traits under divergent selection. This conclusion is robust to different ecological scenarios: niche invasion, adaptive radiation, and secondary contact.

This study suggests that we can expect to find magic traits in most cases of ecological speciation. Also, we can speculate that if we don't find magic traits, it might be because the effect size of the magic traits on survival or mate choice is small (i.e. they are “squib traits”), or because conditions changed such that the once-magic trait lost one of its functions (becoming “muggle traits”). Others speculate even more and interpret this as how women choose men they want to sleep with! That opens up all sorts of interesting pick-up line possibilities; further research is needed, however.

To get to the root of all this, go read the paper, and the F1000 recommendation.

Full reference of the paper:
Thibert-Plante, X. and Gavrilets, S. (2013). Evolution of mate choice and the so called magic traits in ecological speciation, Ecology Letters.