The Darwin-Bateman paradigm recognizes competition among males for access to multiple mates as the main driver of sexual selection. Increasingly, however, females are also being found to benefit from multiple mating so that polyandry can generate competition among females for access to multiple males, and impose sexual selection on female traits that influence their mating success. Polyandry ca...

An increasing body of literature considers the question of how mate choice is influenced by the social environment of the choosing individual (non-independent mate choice). For example, individuals may copy the mate choice of others. A very simple form of socially influenced mate choice, however, remained comparatively little investigated: choosing individuals may adjust their mate choice to th...

Observing sperm in competition has been limited by our ability to discriminate between males' sperm. Recent work has overcome this obstacle, while another study reports on seminal fluid with very specific spermicidal activity, suggesting discrimination is easy for some.

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Females of many animal species store sperm for taxon-specific periods of time, ranging from a few hours to years. Female sperm storage has important reproductive and evolutionary consequences, yet relatively little is known of its molecular basis. Here, we report the isolation of a loss-of-function mutation of the Drosophila melanogaster Acp29AB gene, which encodes a seminal fluid protein that ...

When females are sexually promiscuous, the intensity of sperm competition for males depends on how many partners females mate with. To maximize fitness, males should adjust their copulatory investment in relation to this intensity. However, fitness costs associated with sperm competition may not only depend on how many males a female has mated with, but also how related rival males are. Accordi...

Sperm competition occurs when the sperm of multiple males concurrently occupy the reproductive tract of a female and compete to fertilize an egg. We used a questionnaire to investigate psychological responses to the risk of sperm competition for 237 men in committed, sexual relationships. As predicted, a man who spends a greater (relative to a man who spends a lesser) proportion of time apart f...

Increasing evidence shows that spermatogenesis is costly. As a consequence, males should optimize the use of their sperm to maximize their reproductive outputs in their lifetime. However, experimental evidence on this prediction is largely lacking. Here, we examine how a male moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) responds to the presence of rivals or additional mates and how ...

The copulatory behaviour of male mammals is characterized by striking diversity in patterns of copulatory stimulation and ejaculation frequency. We conducted comparative analyses of rodents to investigate the potential influence of sperm competition in the evolution of copulatory behaviour. We found that increasing sperm competition is associated with faster rates of stimulation and earlier eja...