My group and I research how ecological and evolutionary processes interact to determine the fluctuations of populations. Within this context we focus on identifying the population consequences of variation in the expression of polymorphisms (genetic colour polymorphism in Eleonora's falcon [Laura Gangoso]) en polyphenisms (alternative male reproductive strategies [Tom van den Beuken, Flor Rhebergen] and dispersal polyphenism in bulb mites [Jacques Deere, Kat Stewart]) induced by e.g. environmental change or harvesting. To develop and test our hypotheses we use laboratory experiments on mites, statistical analysis of data and the construction and analysis of mathematical models. We recently applied our methods to field data on threatened populations of reef manta rays to analyse the population consequences of overfishing, and are also applying the models to the bioturbator Orchestia gammarellus in collaboration with Matty Berg (VU).