Ferrière and Le Galliard Invasion fitness and adaptive dynamics in spatial population models 1 INVASION FITNESS AND ADAPTIVE DYNAMICS IN SPATIAL POPULATION MODELS

Disentangling proximate and ultimate factors of dispersal, and assessing their relative effects require an appropriate measure of fitness. Yet there have been few theoretical attempts to coherently define fitness from demographic first principles, when space-related traits like dispersal are adaptive. In this chapter, we present the framework of adaptive dynamics and argue that invasion fitness is a robust concept accounting for ecological processes that operate at the individual level. The derivation of invasion fitness for spatial ecological scenarios is presented. Spatial invasion fitness involves the effect of neighbors on a focal individual, mediated by coefficients analogous to relatedness coefficients of population genetics. Spatial invasion fitness can be used to investigate the joint evolution of dispersal and altruism, two traits that both have a direct influence on, and whose evolution is strongly responsive to, the spatial distribution of individuals. Our deterministic predictions of dispersal and altruism evolution based on spatial invasion fitness are in good agreement with stochastic individual-based simulations of the mutation-selection process acting on these traits. Laboratoire « Fonctionnement et evolution des systèmes écologiques