Griffin et al. (2020a)

Griffin MJ, Holwell GI, Symonds MRE (2020a) Sex ratio and female allocation to harems in a polygynous bark beetle. Austral Entomology 59: 149-155 PDF

What’s the paper about?

The invasive bark beetle Ips grandicollis has the unusual mating system of ‘harem polygyny’, where several females are associated (and mate) with a single male. In this paper we explored what factors determine the size of the harem. For one thing, we found that harems are larger in areas where population density is higher (i.e. in recently felled plantations), but that females change the way they allocate themselves among harems as the number of males available declines. At first, when males are plentiful to choose from they allocate themselves evenly among the males, but as colonisation progresses, females cease to do this and essentially just join whoever.

What’s the story behind it?

This is the second paper out of Melissa’s PhD project (after the excoriating review of ‘harem polygyny’ in insects published in 2019). It makes use of a study system I’ve worked on since the mid 2000s – Ips bark beetles. These lovely little brown torpedoes make a good system for studying this mating system because you can manipulate their environment. That said, you can’t actually easily manipulate, or observe, the harems in flagrante (so to speak), and so it took a while for Melissa to hit upon some successful ways of working on them (including deciding to travel to Queensland to do the field research). However, in the end the hard work bore fruit (unlike the bark beetle whose hard work bore pine logs).

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