Abstract
In the dawn of global change, many ecosystems are facing increasing threat due to environmental stressors. Ecosystems may respond abruptly to gradual environmental changes, leading to significant shifts in their structure and function, known as regime shifts. Alternatively, they can face sudden and severe environmental changes, which can have fatal consequences for many species. Evolutionary dynamics play a crucial role in determining how species respond to these challenges and shape ecosystem dynamics. Understanding the underlying evolutionary processes is crucial for predicting how ecosystems will respond to these challenges. Eco-evolutionary models provide a powerful framework for studying these dynamics, offering insights into how species adapt, evolve, and interact within their changing environments. In this thesis, we study eco-evolutionary dynamics using well established mathematical models and frameworks in ecosystems facing environmental stress. Specifically, we explore the evolutionary outcomes of competitive species in an ecosystem exhibiting ecological regime shifts. Moreover, we investigate the adaptive capacities of an ecosystem facing abrupt environmental shifts.In chapter 1, we explore the impact of rapid trait evolution on ecosystem dynamics and stability in shallow lakes exhibiting alternative stable states. Using a competition model between floating and submerged macrophytes, and employing Adaptive Dynamics (AD) and Quantitative Genetics (QG) approaches, the results reveal complex evolutionary outcomes, including oscillations and evolutionary suicide, where the evolved trait lead to species extinction. This underscores the potential for evolution to destabilize ecosystems and leading spcecies to extinction. However, the research also highlights the stabilizing role of co-evolution, showing that it can prevent oscillations and delay evolutionary suicide, thereby promoting temporary stability, illustrating the nuanced impact of evolutionary processes on ecosystem dynamics.Chapter 2 introduces a mechanistic model describing the dynamics of dormancy and seed production in tree populations. The model accounts for sexual reproduction and environmental factors such as temperature and water availability. This chapter presents a simplification process that involves deriving a macroscopic model from a detailed mechanistic one, using a typical QG result that under weak selection the trait distribution closely resembles a Gaussian centered around the mean traits of the population. The macroscopic model captures the essential dynamics of the system, revealing how trees may respond to abrupt environmental changes through the evolution of mean traits.In chapter 3, we focus on the evolutionary dynamics of seed production and dormancy under climate change, using the macroscopic model derived in Chapter 2 and conducting numerical simulations. The primary questions addressed include the impact of environmental changes, particularly shifts in temperature and precipitation, on the evolutionary strategies of these traits. The study reveals that phenotypic plasticity in dormancy timing can hinder adaptation to temperature shifts, as it prevents reproduction. However, the results also emphasize the importance of the amplitude of precipitation shifts in driving adaptive responses. The co-evolution of seed production and dormancy is shown to enable adaptation to significant environmental shifts. This chapter underscores the complex interplay between temperature and precipitation shifts and highlights the necessity of considering co-evolution and phenotypic plasticity to understand and predict adaptive capacities.