We develop new theory for studying sex-differential selection across a complete life cycle and test our models with genotypic and reproductive success data from approximately 250,000 UK Biobank individuals. We uncover polygenic signals of sex-differential selection affecting survival, reproductive success, and overall fitness.

We measured the effects of prolonged evolution under enforced monogamy or polyandry on the evolution of respiration, activity levels, metabolism, and resistance in the fly Drosophila pseudoobscura. Polyandry flies were more active, and invested more in metabolites associated with increased endurance capacity and efficient energy metabolism and regulation, namely lipids and glycogen.

We examined the fate of experimentally immune-challenged worker honeybees that had been reintroduced to the hive. We find that they often leave the hive, both by ‘altruistically’ leaving under their own power, and by being dragged out by other workers. Using a chemical transfer experiment, we show that the latter response is mediated by chemicals present on the body surface of immune challenged workers.

We find evidence that the mitochondrial DNA carried by Drosophila larvae affects the fitness of other cohabiting larvae – a mitochondrial ‘indirect genetic effect’. This result implies that the effects of mitochondrial DNA on the phenotype of males (specifically, male larvae) may have evolutionary consequences, in contrast to the received wisdom that mtDNA inside males is ‘invisible to selection’ due to maternal inheritance of mtDNA.

We test whether variation in sexual selection can predict speciation and extinction rates across up to 5,812 species of passerine birds. Male‐biased sexual selection, and specifically sexual size dimorphism, predicted two of the three measures of speciation rates that we examined.