Generation Time in Stage-Structured Populations under Fluctuating Environments

A common measure of generation time is the average distance between two recruitment events along a genetic lineage. In populations with stage structure that live in a constant environment, this generation time can be computed from the elasticities of stable population growth to fecundities, and it is equivalent to another common measure of generation time: the average parental age of reproductive-value-weighted offspring. Here, we show three things. First, when the environment fluctuates, the average distance between two recruitment events along a genetic lineage is computed from the elasticities of the stochastic growth rate to fecundities. Second, under environmental stochasticity, this measure of generation time remains equivalent to the average parental age of reproductive-value-weighted offspring. Third, the generation time of a population in a fluctuating environment may deviate from the generation time the population would have in the average environment.

Automated summary

A common measure of generation time is the average distance between recruitment events along a genetic lineage. When the environment fluctuates, the calculation of generation time must take into account the elasticities of the stochastic growth rate to fecundities. Additionally, generation time in fluctuating environments may deviate from the average environment.