Differential stage-specific mortality as a mechanism for diversification

Individual variability in mortality is widespread in nature. The general rule is that larger organisms have a greater chance of survival than smaller conspecifics. There is growing evidence that differential mortality between developmental stages has important consequences for the ecology and evolution of populations and communities. However, we know little about how it can influence diversification. Using an eco-evolutionary model of diversification that considers individual variability in mortality, we show that commonly observed differences in mortality between juveniles and adults facilitate ecological diversification. We find that juvenile-biased mortality reduces the threshold of minimum resource productivity required for diversification. Diversification is hence less restricted when mortality is more biased towards juveniles than when all individuals experience the same mortality rate. This is because, by altering the population composition, juvenile-biased mortality increases the strength of intraspecific competition. Strong intraspecific competition in turn induces frequency-dependent selection, which drives ecological diversification. Our results demonstrate the strong influence that differential mortality between developmental stages has on diversification, and highlight the need for integrating developmental processes into the theoretical framework of diversification.