Recently, the ecological research team from the College of Life Sciences at Beijing Normal University published their findings titled "Seasonal density-dependence can select for partial migrants in migratory species" in Ecological Monographs.

Some representative species with altered migration propensities.

The study reveals the strategy fitness in a seasonal environment and how density dependence in different seasons interacts with density independence to affect the population migratory strategy. Their work provides insights into how and why migration is rapidly changing in the face of environmental changes and also applies the framework for studying eco-evolutionary dynamics in a simplified seasonal structure, providing a way to further explore the rapid evolution of seasonal strategies in nature.

The abstract of the paper is as follows:

Whether, and which, individuals migrate or not is rapidly changing in many populations. Exactly how and why environmental change alters migration propensity is not well understood. We constructed density-dependent structured population models to explore conditions for the coexistence of migrants and residents. Our theoretical models were motivated by empirical data identified via a systematic literature review. We find that the equilibrium density in the season with the strongest density dependence of a strategy predicts whether the strategy will become dominant within the population. This equilibrium density represents strategy fitness in a seasonal environment and can be used to examine selection on migratory behavior. Whether partial migration can be maintained within a population depends on where in the annual cycle density dependence operates. Diversified bet-hedging, where parents produce a mix of migrants and residents, also maintains partial migration. Our study disentangles density-dependent and density-independent rates in a population with seasonal structure, potentially providing routes to explain the rapid change in migration strategies observed in many populations.

Full text link: https://doi.org/10.1002/ecm.70009