Intralocus tactical conflict in JEB

The latest issue of the Journal of Evolutionary Biology features an article by Kyana Pike, Joe Tomkins and myself on a topic that I am fascinated about — the evolutionary conflict between different male phenotypes. In some species, alternative male phenotypes are linked to different tactics for securing matings, where large male morphs express weapons used to defend females or territories (like the thick legs of bulb mites or the forceps of earwigs displayed on the left), whereas small male morphs have reduced weaponry and sneak copulations. In these systems, theory predicts that the evolution of male dimorphism is facilitated if morphs are genetically uncoupled and free to evolve towards their phenotypic optima; however there is little evidence for male morphs responding independently to selection.

One way of investigating the potential for independent or correlated evolution between male morphs is by using quantitative genetics to estimate the heritability and the intrasexual genetic correlations (between male morphs) of dimorphic and monomorphic traits, and comparing them. We did that with two different model systems, and found two contrasting patterns: earwigs exhibited low intrasexual genetic correlations for the dimorphic trait, suggesting that the conflict between male phenotypes is moving towards a resolution. Meanwhile, bulb mites exhibited high and significant intrasexual genetic correlations for most traits, suggesting that morphs in the species may be limited in evolving to their optima. It is surprising, however, that intrasexual dimorphism can evolve to be so evident in this system, despite such strong genetic constraints.

Another very cool aspect of this project is that it emerged from a short project in the unit 'Evolutionary Biology', here at the University of Western Australia. The lead author, Kyana, was at the time doing her honours at UWA with magpies, but Joe and I 'highjacked' her talent and hard work to our bulb mite project, and the result was this beautiful paper!