Diversity within Consequences of individual phenotypic variability on ecological and evolutionary dynamics

Individuals interacting with their environment form the building blocks of ecological systems. Although individual life history variation is increasingly considered when studying population dynamics, the role of phenotypic plasticity in life history merits more attention. This thesis investigates eco-evolutionary consequences of such individual plastic strategies in two universal interactions: acquisition of resources and responses to parasitism.
We studied the effect of plastic feeding strategies when juveniles and adults from a same population experience different feeding environments. Changing diets between life stage is known to generate complex dynamics through stage-specific competition. Our results revealed that stage-specific regulation on population dynamics can dampen the effects of plastic feeding strategies and limit intraspecific variation. On an evolutionary perspective, these stage-specific regulations can promote the evolution of both specialization and plasticity, but limits exploitation of the environmental variability by the population.
We also investigated stage-specific plastic medication strategies in response to infection. We based our model on the medication behaviour of Monarch butterflies (Danaus plexippus) using toxic milkweeds to fight infection. We showed that plastic behaviour increases the efficiency of using toxic plants for medication. Differential preference behaviours in infected and healthy individuals can even benefit the population through increased birth rate. In addition, evolution of a plastic medication response can eradicate the infection and occurs regardless of the level of parasite virulence or plant toxicity.
This thesis, by exploring different intraspecific processes at eco-evolutionary scales demonstrates the importance of incorporating individual life history variation when exploring eco-evolutionary processes.