Does Sexual Selection Accelerate or Slow Speciation in Arctic Shorebirds?

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Sexual selection has often been assumed to promote speciation, as it is typically associated with one sex being particularly selective about their mate, which enhances reproductive isolation (Lande, 1981). However recent research by D'Urban-Jackson et al. (2017), found that in shorebirds, the higher levels of sexual selection found in polygamous mating systems were associated with reduced levels of reproductive isolation. The authors suggest this is due to a more direct effect of polygamy on gene flow - by mating and moving on and mating again, an individual can mix its genes into multiple populations every season. Ecological factors are also associated with both mating system and gene flow, and these have confounded previous investigations (including that of D'urban Jackson et al., 2017). The planned research will compare population structure in ~10 phylogenetically controlled species of Arctic Shorebird, with almost identical breeding ranges and habitats, but with varying levels of sexual selection present. For the first time the role of sexual selection in reproductive isolation will be investigated in the absence of ecological confounds. Reproductive isolation will be analysed using high-throughput genomics, with support from CASE partner the Beijing Genomics Institute. This planned analysis will require multiple Arctic field seasons as well as collaboration (with support from ÉLVONAL), and sample collection is not expected to be complete until towards the end of the PhD. More immediate plans are: 1) to analyse the effect of mating system on sex-biased gene expression, for the first time using wild birds (see Harrison et al., 2015 for such an analysis in semi-domesticated birds). And 2) to analyse temporal genetic diversity changes for the first time in an Arctic bird, the Ringed Plover (see Boessenkool et al., 2010, for a similar methodology in penguins). The planned studies have a clear relation to the National Envrionment Research Council aims, as understanding the factors underlying reproductive isolation can help conservationists predict which species are most at risk of extinction. This is particularly applicable given the Arctic location of the birds studied, where many species are already in rapid decline and where the effects of climate change are felt most keenly (reviewed in Meltofte, 2007). Boessenkool, S., Star, B., Seddon, P. J., & Waters, J. M. (2010). Temporal genetic samples indicate small effective population size of the endangered yellow-eyed penguin. Conservation Genetics, 11(2), 539-546.D'Urban Jackson, J., Dos Remedios, N., Maher, K. H., Zefania, S., Haig, S., Oyler-McCance, S., ... & Kupper, C. (2017). Polygamy slows down population divergence in shorebirds. Evolution, 71(5), 1313-1326.Harrison, P. W., Wright, A. E., Zimmer, F., Dean, R., Montgomery, S. H., Pointer, M. A., & Mank, J. E. (2015). Sexual selection drives evolution and rapid turnover of male gene expression. Proceedings of the National Academy of Sciences, 112(14), 4393-4398.Lande, R. (1981). Models of speciation by sexual selection on polygenic traits. Proceedings of the National Academy of Sciences, 78(6), 3721-3725.Meltofte, H. (Ed.). (2007). Effects of climate variation on the breeding ecology of Arctic shorebirds. Museum Tusculanum Press.