My lab has recently started a new initiative called JournalPub! (I believe the exclamation mark is essential). The idea is that this is a weekly event and anyone interested goes to the pub to read and discuss a classic or important paper. So far its been focussing on the Heliconius literature, although it needn’t be restricted to that. The difference from a typical journal club is that there is no expectation to attend if you dont want to read the paper, and that you dont have to read anything before turning up. Oh, and there is beer available at the bar. A further development is that we hope to write a short post about each paper on this blog, to start to generate an annotated list of some interesting or important Heliconius literature.
So I went for the first time last night and we discussed this paper:
I am quite familiar with the paper already, since it was fairly recently published when I started my graduate studies with Jim in 1993. He had spent over a year living in Peru with a battered LandCruiser, translocating butterflies across a hybrid zone in order to measure selection in the wild. The essence of the experiment is that butterflies were translocated, marked and released. Controls were moved to a population in which they had the same wing pattern as the local butterflies, while experimentals were moved a similar distance but into a population with a very different wing pattern. So-called Native Controls were locally marked and released back into their own population. A likelihood approach (calculated manually in those days) was used to fit two parameters – a probability of establishment and a subsequent probability of survival. The Experimentals had a greatly reduced probability of establishment as compared to controls, but subsequent survival was similar for both. This suggests an initial strong burst of predation soon after release. Possibly the birds are likely to attack novel patterns at first but there are only a few predators in the local area and they soon learn the novel pattern also.
The paper also discussed alternative explanations for thre reduced survival of experimentals – notably some other form of local adaptation unrelated to wing pattern. Translocation distance had no effect on survival arguing against this explanation although it is hard to rule out completely. The authors say in the discussion that ‘..it would be perverse to assume that selection due to predation is unimportant.’ – thats perhaps over-egging the pudding a bit, but perhaps a little bit of frustration with reviewers was showing through at this point.
The paper was important, as it still stands as perhaps the best experimental demonstration of mimicry selection in the wild and provides an explanation for the stability of narrow wing pattern hybrid zones in Heliconius.
When things were going badly in the field, I was always inspired by Jim’s story of this experiment – having spent six months collecting data he was disillusioned and depressed about the lack of significant results. Nick Barton, like the messiah of evolutionary biology, came down to visit. On a pocket calculator he worked out a likelihood model and showed that the experiment was significant. Time for a bottle of Cusquenya?