KR Ashman, KB McNamara, MRE Symonds (2016) Experimental evolution reveals that population density does not affect moth signalling behaviour and antennal morphology. Evolutionary Ecology 30: 1009-1021
What’s it about?
We tested the prediction that environmental density should select for optimal strategies in terms of investment in structures and behaviours associated with mate attraction and location. Using experimental evolution lines of the pantry moth, Plodia interpunctella, that had been reared for 35 generations at either high or low density, we examined whether there had been any genetic-based changes in male antennae morphology (prediction: males from high-density lines should have smaller antennae, as they would have less difficulty finding mates) and female pheromone calling behaviour (females from high-density lines should call less intensively, for the same reason). We actually found no difference between individuals from the different lines, which is interesting because previous analyses have detected similar differences in moths reared immediately in one generation under these conditions – suggesting that any differences observable between densities is an environmental plastic response, not an evolutionary one.
What’s the story behind it?
I have had interests for some years in moth antennal evolution (a collaboration I started with Mark Elgar), and in 2014 I advertised for an honours student to look at variation in antennal size and calling behaviour in moths in relation to population density, the latter following on, in part, from the paper on female signalling strategies in moths that I wrote with Kate Umbers and Hanna Kokko. Kita was the lucky honours student who took on the project. However, in a serendipitous event – in January of 2015, about a month before Kita was due to start, I received an email from an old friend, Kath McNamara at the University of Western Australia, that said something along the lines of “hey I’ve got these experimental lines of moths that I’m trying to find interesting questions to test with, would you have an honours student who might be interested in doing something with them”. The fit with what Kita and I were planning to do was perfect, and now we could do the project with a whole production line of moths, and in a way that was much more interesting (we weren’t really expecting to be able to do experimental evolution in a 9 month project). Well, Kita did a fantastic job. She was almost the perfect honours student. She did all the grunt work without complaint (well, OK, she allowed herself the occasional martyr’s sigh), produced a great thesis, and then has written up a paper which got accepted with only minor revisions in pretty quick time! On top of that, she remembered my birthday from me having mentioned it once about 4 months earlier, and bought me a present – so all told, she’s very much in my good books.