Seasonal and genotypic influences on life cycle synchronisation: further insights from annual squid

We consider a simple individual-based model which incorporates a two stage growth response for squid hatchlings in continual exposure to seasonal fluctuations of temperature. In the first stage of growth an individual increases rapidly in size at a temperature-dependent rate. After a fixed period of time, an abrupt transition occurs to a temperature-independent growth rate, which is maintained for the rest of the lifespan. In exposure to seasonally fluctuating temperatures such a growth mechanism is shown to directly induce phenotypic variability. By assuming that an individual’s developmental progress is related to the same phenotypic trait, we are able to consider the temporal dynamics generated. Stochastic simulations show that provided genotypic variability is low, synchronisation can be maintained only by recruitment to a single population occurring up to (at most) a few times of year.