Many studies have demonstrated influences of climatic variation on a variety of ecological processes, however, its impact on the potent evolutionary force of sexual selection has largely been ignored. The intensity of sexual selection is a fundamental parameter in animal populations, which depends upon the degree of polygamy and will probably be influenced by the impact of local climatic variation upon 'environmental potential for polygamy'. Here, we provide evidence of a direct effect of local climatic variation on the intensity of sexual selection, by showing a clear correlation between local weather conditions and inter-annual changes in the degree of polygamy in a long-term study of colonially breeding grey seals (Halichoerus grypus). Our results show that changes in local weather conditions alter the annual proportion of males contributing to the effective population size (Ne) by up to 61%. Consequently, over the 'lifetime' of a cohort, a broader range of individuals will contribute genetically to the next generation if local weather conditions are variable. In the context of predicted future changes in climatic variation, these findings have broad implications for population genetics of socially structured animal systems through the major influence that the degree of polygamy has upon Ne.

Sperm are exposed to substantially different environments during their life history, such as seminal fluid or the female sexual tract, but remarkably little information is currently available about whether and how much sperm composition and function alters in these different environments. Here, we used the honeybee Apis mellifera and quantified differences in the abundance and activity of sperm proteins sampled either from ejaculates or from the female’s sperm storage organ. We find that stored and ejaculated sperm contain the same set of proteins but that the abundance of specific proteins differed substantially between ejaculated and stored sperm. Most proteins with a significant change in abundance are related to sperm energy metabolism. Enzymatic assays performed for a subset of these proteins indicate that specific protein activities differ between stored and ejaculated sperm and are typically higher in ejaculated compared to stored sperm. We provide evidence that the cellular machinery of sperm is plastic and differs between sperm within the ejaculate and within the female’s storage organ. Future work will be required to test whether these changes are a consequence of active adaptation or sperm senescence and whether they alter sperm performance indifferent chemical environments or impact on the cost of sperm storage by the female.However, these changes can be expected to influence sperm performance and therefore determine sperm viability or sperm competitiveness for storage or egg fertilization.

No abstract