Sexual Selection and Sperm Competition Dynamics
Summary
Sexual selection and sperm competition represent key forces shaping reproductive strategies and trait evolution across the animal kingdom. Sexual selection arises whenever individuals vary in mating success due to trait differences, leading to the evolution of ornaments, weapons or behaviours that enhance access to mates. Following copulation, sperm competition occurs when ejaculates from multiple males compete to fertilise a given set of ova, driving adaptations in ejaculate allocation, sperm morphology and timing of mating. Together, these processes interact with female‐mediated mechanisms—such as cryptic female choice and reproductive tract architecture—to determine paternity outcomes. The dynamic interplay of pre- and postmating selection episodes underlies the extraordinary diversity in mating systems, gamete design and parental care strategies observed in nature. Understanding these interactions reveals how genetic compatibility, environmental context and sex-specific investment co-evolve to shape reproductive fitness.
Research from Nature Portfolio
Recent studies have used individual-based simulations to demonstrate that transient polymorphisms in parental care strategies can drive rapid shifts in sex roles, revealing that sexual selection often follows rather than leads patterns of maternal or paternal care. In avian systems, machine-learning analyses of sperm competition experiments indicate that insemination order and timing often exert greater influence on fertilisation success than intrinsic ejaculate quality, emphasising the nuanced interplay between male traits and female-mediated factors. Work on external fertilizers has uncovered that ovarian fluid modulates sperm motility and chemoattraction, enabling females to bias paternity post-mating by enhancing the performance of preferred sperm, and thereby extending the scope of cryptic female choice to taxa with external fertilisation.
Sexual Selection and Sperm Competition Dynamics publication trend
The graph below shows the total number of articles in sexual selection and sperm competition dynamics across all publications each year (not limited to Nature Index journals).
Technical terms
Anisogamy: The production of gametes of differing sizes by males and females, fundamental to sex-role differentiation.
Polyandry: A mating system in which a female mates with multiple males, often promoting sperm competition and genetic diversity.
Cryptic female choice: Post-mating mechanisms by which females bias the use of sperm from different males to influence paternity.
Sperm competition: The contest between sperm of two or more males to fertilise the eggs of a single female.
Operational sex ratio (OSR): The ratio of sexually competing males to fertilisable females at any given time, influencing mating dynamics.
References
- Transient polymorphisms in parental care strategies drive divergence of sex roles. Nature Communications (2023).
- Interplay between male quality and male-female compatibility across episodes of sexual selection. Science Advances (2023).
- Sex-specific assumptions and their importance in models of sexual selection. Trends in Ecology & Evolution (2023).
- Ranking parameters driving siring success during sperm competition in the North African houbara bustard. Communications Biology (2023).
- Polyandry in nature: a global analysis. Trends in Ecology & Evolution (2014).
- Ovarian fluid allows directional cryptic female choice despite external fertilization. Nature Communications (2016).
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