Sex allocation is the allocation of resources to male versus female reproduction. This single body of theory unifies questions such as: (a) When and how should individuals adjust the sex of their offspring in response to environmental conditions? (b) When and in what direction are individuals selected to change sex? We have a very good understanding of the selective forces that influence sex allocation, and so work in this area offers excellent opportunities to address general questions in evolutionary biology, such as the constraints on adaptation or usefulness of different approaches.

Recent and ongoing projects

• Precision of sex ratio adjustment in the parasitoid wasp Nasonia vitripennis
• Sex change in reef fish and other animals
• Sex ratios in malaria parasites (Plasmodium) and other parasitic protozoa
• Differences in precision of sex ratio adjustment across animal taxa, especially insects, birds, and mammals

Selected Relevant Publications

• West, S.A. (2009) Sex Allocation. Princeton University Press (Monographs in Population Biology Series).
• Wild, G. & West, S.A. (2009) Genomic imprinting and sex allocation. American Naturalist 173, E1-E14.
• Burton-Chellew, M.N., Koevoets, T., Grillenberger, B.K, Sykes, E.M., Underwood, S.L., Bijlsma, K., Gadau, J., van de Zande, L., Beukeboom, L.W., West, S.A. & Shuker, D.M. (2008) Facultative sex ratio adjustment in natural populations of wasps: cues of local mate competition and the precision of adaptation. American Naturalist 172, 393-404.
• Pannebakker, B.A., Halligan, D.L., Reynolds, K.T., Ballantyne, G.A., Shuker, D.M., Barton, N. & West, S.A. (2008) Effects of spontaneous mutation accumulation on sex ratio traits in a parasitoid. Evolution 62, 1921-1935.
• Gardner, A., Hardy, I.C.W., Taylor, P.D. & West. S.A. (2007) Spiteful soldier production in polyembryonic parasitoid wasps. American Naturalist 169, 519-533.
  
• Wild, G. & West, S.A. (2007) A sex allocation theory for vertebrates: combining local resource competition and condition-dependent allocation. American Naturalist 170, E112-E128.
  
• Griffin, A.S., Sheldon, B.C. & West, S.A. (2005) Cooperative breeders adjust offspring sex ratios to produce helpful helpers. American Naturalist 166, 628-632. {PDF}
  
• Shuker, D.M., Pen, I., Duncan, A.B., Reece, S.E. & West, S.A. (2005) Sex ratios under asymmetrical local mate competition: theory and a test with parasitoid wasps. American Naturalist 166, 301-316.
• West, S.A., Shuker, D.M. & Sheldon, B.C. (2005) Sex ratio adjustment when relatives interact: a test of constraints on adaptation. Evolution 59, 1211-1228. {PDF}
• Allsop, D.J. & West, S.A. (2004) Sex ratio evolution in sex changing animals. Evolution, 58, 1019-1027. {PDF}
  
• Sheldon, B.C & West, S.A. (2004) Maternal Dominance, maternal condition, and offspring sex ratio in ungulate mammals. American Naturalist, 163, 40-54. {PDF}  {Supplementary Info}  {Media}
  
• Shuker, D.M. & West, S.A. (2004) Information constraints and the precision of adaptation. Proceedings of the National Academy of Science, USA, 101, 10363-10367. {PDF}   {Current Biology Commentary}
  
• West, S.A. & Sheldon, B.C. (2002) Constraints in the evolution of sex ratio adjustment. Science, 295, 1685-1688. {PDF} {PDF of TREE commentary} {Supplementary Information} 
• West, S.A., Reece, S.E. & Read, A.F. (2001) The evolution of gametocyte sex ratios in malaria and related apicomplexan (protozoan) parasites. Trends in Parasitology, 17, 525-531. {PDF}
• West, S.A., Herre, E.A. & Sheldon, B.C. (2000) The benefits of allocating sex. Science, 290, 288-290. {PDF}
• West, S.A. & Herre, E.A. (1998) Stabilizing selection and variance in fig wasp sex ratios. Evolution, 52, 475-485. {PDF}