Starving to grow: The ecology and evolution of growth curve plasticity

All organisms grow in size throughout their life. Some species display a largely constant growth curve, while the growth curve of other species is largely plastic and therefore strongly depends on environmental factors such as the resource availability. This thesis explores how the level of growth curve plasticity affects the ecological and evolutionary dynamics of a population. On the individual level, growth curve plasticity is tightly intertwined with the energy allocation schemes of an individual and the energetic trade-offs between growth, reproduction and maintenance. This is modeled using a simple dynamic energy budget model. Fluctuations in the environment accumulate in the size of individuals if growth is largely plastic. As a consequence, the level of growth curve plasticity strongly influences the size-structure of a population. This size-structure can therefore contain valuable information about the environmental limitations experienced by a population. The first part of this thesis explores how this information can be deduced from size measurements of individuals from natural populations such as North Sea fish stocks. The second part of this thesis uses size-structured models to show that the dynamics of a population is driven by limitations in either growth or reproduction. These two regimes show differences in the population structure, the occurrence and type of population dynamic cycles, the effects of harvesting and optimal fishing strategies. Overall, this thesis shows that the level of growth curve plasticity should be considered when exploring the dynamics of structured populations on any level of biological organization.

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