Symonds and Gitau-Clarke (2016)

Symonds MRE, Gitau-Clarke CW (2016) The evolution of aggregation pheromone diversity in bark beetles. Advances in Insect Physiology 50 195-234

What’s it about? A review of what is known about the aggregation pheromone composition from scolytine bark beetles (the type that typically aggregate and burrow into the phloem underneath the bark of coniferous trees – the ones that kill loads of pine trees in North America, of which we have only one, comparatively benign, species in Australia). We look at the relationship between pheromone composition and phylogeny and identify that, while there tends to be considerable diversity, even between closely-related species, there are interesting patterns in terms of use of particular chemical compounds. Some compounds are highly conserved on the phylogeny (i.e. once they evolve, they tend to be consistently used), while others appear to be switched-on and switched-off relatively freely depending on the species. These patterns suggest interesting mechanisms in regard to how species-specific pheromone blends evolve.

What’s the story behind it? Catherine Gitau was always someone I knew I should work with, because she was the only other person actively working on the bark beetle Ips grandicollis in Australia. I’d kept on wanting to meet her at conferences etc, but always just missed her (“oh she was here earlier, she had to go and catch a plane”). Eventually, she emailed me out of the blue when she moved (temporarily) to a country town near Melbourne with her husband. I was just taking on my honours student Alison, who was working on bark beetles, and thought this was an excellent opportunity to forge a collaboration. At the very same time I had an email from Claus Tittiger and Gary Blomquist (bark beetle research godfathers) who were putting together volume 50 of Advances in Insect Physiology, a book series/cum journal, and wanted me to contribute a chapter of the evolution of aggregation pheromones in bark beetles. Funnily enough, I had been thinking for some time of updating and expanding my earlier analysis of bark beetle  pheromone evolution, using better methods, phylogeny and more complete data – so this provided a great opportunity. Since Catherine had also recently published a review of bark beetle pheromones it seemed like the perfect opportunity to write something together. We were given a year deadline to write the paper, and in classic academic tradition we left it to the last month to do it all (in terms of turnaround, this paper is probably the quickest one I’ve ever written). But it turned out really nicely, and actually the whole process was a lot smoother, both in terms of writing and journal handling, than most of my papers. It was nicely also to revisit the little critters who started my interest in pheromone evolution.

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