The past several decades have seen a proliferation of research on sperm competition, stemming from the fundamental insight that the processes of sexual selection identified by Darwin (mating competition and mate choice) will often extend beyond the point of copulation. In species where females mate with multiple males (or have the potential to do so), we can expect adaptations in males to either engage in or avoid sperm competition and hence maximize their fertilization success; adaptations in females to ensure sperm from only preferred males fertilize their eggs (cryptic female choice); and adaptations in both sexes to the fact that the reproductive interests of males and females will frequently diverge (sexual conflict). Our research embraces all of these aspects, using a combination of theory and experiments.
Current theoretical effort focuses on predicting how males should respond to variation in female quality and sperm competition level by altering investment in ejaculates, sperm number and sperm viability. Current empirical projects include studying nuptial gifts, strategic mating effort, and phenotypic plasticity of sperm traits in scorpionflies; the genetics and evolution of sperm morphological and production traits in simultaneously hermaphroditic flatworms; and phenotypic plasticity and evolution of sperm traits resulting from extra-pair paternity in wild populations of socially monogamous birds.
Cryptic female choice in grasshoppers:
Sperm competition in birds:
Ramm, S.A. & Stockley, P. (2014) Sequential male mate choice under sperm competition risk. Behavioral Ecology | DOI
Engqvist, L., Cordes, N., Schwenniger, J., Bakhtina, S. & Schmoll, T. (2014) Female remating behaviour in a lekking moth. Ethology | DOI
Cordes, N., Yiğit, A., Engqvist, L. & Schmoll, T. (2013) Differential sperm expenditure reveals a possible role for post-copulatory sexual selection in a lekking moth. Ecology and Evolution 3: 503-511.
Reinhold, K. & Ramm, S.A. (2013) Male control of sperm transfer dynamics in a spermatophore-donating bushcricket. Behavioral Ecology and Sociobiology 67: 395–398.