I am interested in how underlying genetic and epigenetic architecture can influence or potentially constrain the evolution of complex traits. I am currently investigating the mechanism underlying sex allocation behaviour in the parasitoid wasp Nasonia vitripennis.
The study of sex allocation has produced some of the best and most elegant tests of evolutionary theory to date (Reviewed by West 2009 and Charnov 1982) and our knowledge of how natural selection shapes sex allocation is very well-developed. Nasonia vitripennis has become something of a model species for the study of sex ratio at the phenotypic level and with genomic resources now available (Werren et al. 2010) is an ideal system to study mechanistic constraints on evolution.
Female wasps allocate offspring sex in line with Local Mate Competition (LMC) theory (Hamilton 1967), altering the sex ratio of their brood(s) in line with the level of LMC their sons will experience. Female-biased sex ratios are produced when one or few females lay eggs on a patch but as the number of females contributing offspring to a patch increases, more male-biased sex ratios are favoured. Since Hamilton’s original LMC model, sex allocation research has filled in many of the gaps relating to the cues females use to allocate sex and has explained a large part of the variation in sex ratios produced (Werren 1980, 1984, Shuker et al. 2004a, 2004b, 2005). However, this is only one part of the evolutionary story. More recent sex allocation research has begun to unravel the mechanisms underlying this behaviour using quantitative genetic approaches and RNA-seq technologies (Pannebakker et al. 2008, 2011, 2013) but we are still a long way from understanding how sex allocation is genetically controlled.
I am currently using technologies such as RNA-seq, GWAS and DNA methylation inhibition (Cook et al. 2015) to delve deeper into how genetic and epigenetic mechanisms regulate this fascinating behaviour.
2013- Present NERC Post-doc, University of St Andrews, UK.
2012-2013 BBSRC Post-doc, University of Dundee, UK.
2008-2011 PhD. “Population genetics of the farmland sawfly Dolerus aeneus“, The James Hutton Institute, UK.
2002-2007 BSc. (Hons) Zoology, University of Dundee, UK.
Cook, N., Trivedi, U., Pannebakker, B.A., Blaxter, M., Ritchie, M.G., Tauber, E., Sneddon, T. and Shuker, D.M. (2015) Oviposition but not sex allocation is associated with transcriptomic changes in females of the parasitoid wasp Nasonia vitripennis. G3: Genes| Genomes| Genetics, 5: 2885-2892.
Baker, K., Dhillon, T., Colas, I., Cook, N., Milne, I., Cardle, L., Bayer, M. & Flavell, A. (2015) Chromatin state analysis of the barley epigenome reveals a higher order structure defined by H3K27me1 and H3K27me3 abundance. The Plant Journal, DOI: 10.111/tpj.12963.
Cook, N., Pannebakker, B.A., Tauber, E. & Shuker, D.M. (2015) DNA methylation and sex allocation in the parasitoid wasp Nasonia vitripennis. The American Naturalist, 186: 513-518.
Whitehorn, P.R., Cook, N., Blackburn, C.V., Gill, S.M., Green, J. & Shuker, D.M. (2015) Neonicotinoids disrupt adaptive facultative sex allocation in a beneficial insect. Proceedings of the Royal Society, Series B, 282: 20150389.
Shuker, D.M. & Cook, N. (2014) Evolution: conflict by the sexes, for the sexes. Current Biology, 24(23): pR1135-pR1137.
Baker, K., Bayer M., Cook, N., Dreißig, S., Dhillon, T., Russell, J.R., Hedley, P.E., Morris, J., Ramsay, L., Colas, I., Waugh, R., Steffenson, B., Milne, I., Stephen, G., Marshall, D. & Flavell, A.J. (2014) The low recombining pericentromeric region of barley restricts gene diversity and evolution but not gene expression. The Plant Journal, 79: 981-992.
Cook, N., Hubbard, S.F., Karley, A.J. & Russell, J.R. (2013) Genetic diversity and Complementary Sex Determination (CSD) in Dolerus aeneus (Hymenoptera, Symphyta): implications for the conservation of an ecologically-important sawfly. Conservation Genetics 4(6): 1125-1133.
Cook, N., Aziz, N., Hedley, P.E., Morris, J., Milne, L., Karley, A.J., Hubbard, S.F. & Russell, J. R. (2011) Transcriptome sequencing of an ecologically important graminivorous sawfly: a resource for marker development. Conservation Genetics Resources 4: 789-795.
Charnov, E.L. (1982) The theory of sex allocation. Princeton University Press.
Cook, N. (2015) Am. Nat. DOI: 10.1086/682950.
Hamilton, W.D. (1967) Science 156, 477-488.
Pannebakker, B.A. et al. (2008) Evolution 62, 1921-1935.
Pannebakker, B.A. et al. (2011) J. Evol. Biol. 24, 12-22.
Pannebakker, B.A. et al. (2013) PloS one 8, e68608.
Shuker, D.M. et al. (2004a) PNAS 101, 10363-10367.
Shuker, D.M. et al. (2004b) Evol. Ecol. Res. 6, 473-480.
Shuker, D.M. et al. (2005) Am. Nat. 166, 301-316.
Werren, J.H. (1980) Science 208, 1157-1159.
Werren, J.H. (1984) Neth. J. Zool. 34, 123-143.
Werren, J.H. et al. (2010) Science 327, 343-348.
West, S.A. (2009) Sex Allocation. Princeton University Press.