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Population density effects on gamete traits and fertilisation dynamics under varying sperm environments in mussels
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  • Craig Sherman,
  • Vincent Careau,
  • Clelia Gasparini,
  • Kim Weston,
  • Jonathan Evans
Craig Sherman
Deakin University Faculty of Science Engineering and Built Environment

Corresponding Author:[email protected]

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Vincent Careau
University of Ottawa
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Clelia Gasparini
University of Padova
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Kim Weston
Deakin University Faculty of Science Engineering and Built Environment
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Jonathan Evans
The University of Western Australia
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Abstract

Gamete traits can vary widely among species, populations and individuals, influencing fertilisation dynamics and overall reproductive fitness. Sexual selection can play an important role in determining the evolution of gamete traits with local environmental conditions determining the strength and direction of sexual selection. Here we test for signatures of post-mating selection on gamete traits in relation to population density, and possible interactive effects of population density and sperm concentration on sperm motility and fertilisation rates among natural populations of mussels. Our study shows that males from high density populations produce smaller sperm compared with males from low density populations, but we detected no effect of population origin on egg size. Our results also reveal that females from low density populations tended to exhibit lower fertilisation rates across a range of sperm concentrations, although this became less important as sperm concentration increased. Variances in fertilisation success were higher for females than males and the effect of gamete compatibility between males and females increases as sperm concentrations increase. These results suggest that local population density can influence gamete traits and fertilisation dynamics but also highlight the importance of phenotypic plasticity in governing sperm-egg interactions in a highly dynamic selective environment.
30 Oct 2023Submitted to Ecology and Evolution
31 Oct 2023Assigned to Editor
31 Oct 2023Submission Checks Completed
03 Nov 2023Reviewer(s) Assigned