This research line aims at understanding the fitness bases of cooperation and the consequences of cooperation for population dynamics through its effects on reproductive output, survival and dispersal. Understanding how cooperation evolves under the competition imposed by natural selection on individuals is a persistent problem in biology. Individuals cooperate at an apparent cost to themselves and to the benefit of the group. This poses an evolutionary problem because, while cooperative groups do better than non‐cooperative groups, each individual in a group benefits from acting selfishly and letting the others work. Selfishness leads to the collapse of cooperation; yet, cooperation is widespread from unicellular organisms to humans.
How is cooperation maintained? After several decades of research there are major answers, but also some important gaps in our knowledge. First, cooperation may be stable if it occurs between related individuals (kin selection). An additional and non‐exclusive explanation is that cooperation is selfish, by providing direct fitness benefits. To date the direct benefits of helping have been poorly investigated in non‐human societies. We are conducting experiments and using long‐term data from natural populations to determine the relative importance of direct and indirect benefits in the evolution of cooperation. Our study model is an endemic passerine bird from southern African passerine and this project will continue a long‐term field‐ based study which is unique for African birds. We will focus on the evolution of different cooperative behaviours – cooperative breeding, nest building and predator mobbing and on the relationship between cooperation, fitness, dispersal and long‐term population dynamics.

Living on islands is thought to lead to the evolution of specific behavioural, ecological and physiological adaptations, but with the exception of morphological evolution in island mammals, systematic tests of patterns of adaptation on islands have been scarce. Reduced pressure from predators and parasites and inflated population densities are expected to change drastically on islands. Whether insularity does indeed lead to a significant reduction in parasite pressure remains unknown. We are thus studying how host‐parasite interactions are affected by insularity and induce cascading effects on sexually selected traits. Moreover, host-parasite interactions are closely affected by animal endocrinology, which is also expected to vary in island species. Finally, we are integrating the study of host‐parasite interactions with physiology and the variability of sexual signals on islands. Our project is based on solid and complementary multidisciplinary approaches that will significantly improve our knowledge on the processes involved in the evolution of adaptations to insularity and on the evolution of ornamentation and reproductive strategies in general.