Periodic Reporting for period 1 - DYNAMICTRIO (Feedback between population dynamics and evolution of interactions in a tri-trophic system)
Periodo di rendicontazione: 2022-10-01 al 2025-03-31
To understand how ecosystems survive in a changing world, we need to investigate the interplay between ecology (species interactions with each other and the environment) and evolution (how species adapt over time). While these processes are known to be connected, most studies fail to fully investigate the consequences of eco-evolutionary feedbacks for species survival and ecosystem resilience.
Theoretical studies suggest that evolutionary changes in species can stabilize ecosystems and improve recovery after disturbances. However, we lack empirical evidence to confirm these predictions. What is also not well understood is how the stability of an ecosystem influences the evolution of species that compose it. In short, we need more studies to figure out how ecosystem stability and evolutionary changes affect each other.
Moreover, most studies on eco-evolutionary dynamics focus on interactions between just two species. While this makes it easier to understand how evolution can affect species interactions, it is also a problem, since in nature, species rarely interact in isolation; there are often indirect effects from other species in the ecosystem. However, we still lack information on how evolution happens within more complex systems and how indirect effects can shape eco-evolutionary feedbacks.
In the DYNAMICTRIO project, we aim to fill these gaps. For that we study a simple ecosystem made up of plants (Brassica rapa), herbivores (the spider mite, Tetranychus urticae), and predators (Amblyseus swirskii). We use a combination of experimental real time evolution, phenotyping, characterization of genetic changes, mathematical modelling and simulations to understand:
1- How the dynamics of this ecosystem change with different levels of resources (productivity) and environmental stress.
2- How changes in the population dynamics of species and the stability of the ecosystem affect the evolution of these species, and vice versa.
3- How evolutionary changes in one species can impact both direct and indirect relationships between organisms, and how this affects the resilience of the entire ecosystem in different environments.
4- How eco-evolutionary changes at different levels (individual, populations and entire ecosystems) can influence the long-term survival and stability of ecosystems.
The main goal of DYNAMICTRIO is to understand how ecological and evolutionary changes feed into each other and how these feedbacks help ecosystems persist and adapt to change.
Theoretical studies suggest that evolutionary changes in species can stabilize ecosystems and improve recovery after disturbances. However, we lack empirical evidence to confirm these predictions. What is also not well understood is how the stability of an ecosystem influences the evolution of species that compose it. In short, we need more studies to figure out how ecosystem stability and evolutionary changes affect each other.
Moreover, most studies on eco-evolutionary dynamics focus on interactions between just two species. While this makes it easier to understand how evolution can affect species interactions, it is also a problem, since in nature, species rarely interact in isolation; there are often indirect effects from other species in the ecosystem. However, we still lack information on how evolution happens within more complex systems and how indirect effects can shape eco-evolutionary feedbacks.
In the DYNAMICTRIO project, we aim to fill these gaps. For that we study a simple ecosystem made up of plants (Brassica rapa), herbivores (the spider mite, Tetranychus urticae), and predators (Amblyseus swirskii). We use a combination of experimental real time evolution, phenotyping, characterization of genetic changes, mathematical modelling and simulations to understand:
1- How the dynamics of this ecosystem change with different levels of resources (productivity) and environmental stress.
2- How changes in the population dynamics of species and the stability of the ecosystem affect the evolution of these species, and vice versa.
3- How evolutionary changes in one species can impact both direct and indirect relationships between organisms, and how this affects the resilience of the entire ecosystem in different environments.
4- How eco-evolutionary changes at different levels (individual, populations and entire ecosystems) can influence the long-term survival and stability of ecosystems.
The main goal of DYNAMICTRIO is to understand how ecological and evolutionary changes feed into each other and how these feedbacks help ecosystems persist and adapt to change.
Creation of an ecosystem in a box
We have created small experimental ecosystems inside boxes to study evolution in a tri-trophic system. Each ecosystem contains 80 Brassica rapa plants, which complete their life cycle in 56 days, and can be infested with herbivores and predators. We’ve also developed methods to measure herbivore and predator populations with minimal disturbance.
Characterizing the tri-trophic system
We characterized each species of our ecosystem in isolation and how they interact. Specifically, we tracked growth, development, and reproduction for each species. We also studied how predatory mites hunt and feed on spider mites, including how their feeding rates change depending on the density and life stages of the prey. Finally, we estimated fitness costs associated with the different types of interactions, including the impact of spider mite herbivory on plant growth and seed production and changes in prey population size in the presence of different predator abundances.
Quantifying genetic variation in the response to multiple stresses in plants
We studied how different plant genotypes respond to herbivory and competition. We found that herbivory reduced seed production, and this effect was more pronounced under competition. However, some plants were more affected by herbivory and others by competition, which suggests that there is genetic variation on our plant populations to respond to different environmental pressures.
Developing a model to connect system stability and fitness
Along with colleagues from the University of St. Andrews, we are developing a theoretical model that combines kin selection theory and predator-prey dynamics. We have already described how the ecosystem behaves considering only ecological dynamics and we are currently working to include evolutionary dynamics.
Predicting stability in complex ecosystems
In collaboration with colleagues from Doñana’s Biological Station and the Faculty of Sciences of Lisbon, we applied the structural stability framework to better understand how herbivore competition and evolution shapes coexistence between species. In a step further, our aim is to apply this framework to our tri-trophic system. This will help us predict the long-term stability of our ecosystem, without needing to rely heavily on temporal experimental data.
We have created small experimental ecosystems inside boxes to study evolution in a tri-trophic system. Each ecosystem contains 80 Brassica rapa plants, which complete their life cycle in 56 days, and can be infested with herbivores and predators. We’ve also developed methods to measure herbivore and predator populations with minimal disturbance.
Characterizing the tri-trophic system
We characterized each species of our ecosystem in isolation and how they interact. Specifically, we tracked growth, development, and reproduction for each species. We also studied how predatory mites hunt and feed on spider mites, including how their feeding rates change depending on the density and life stages of the prey. Finally, we estimated fitness costs associated with the different types of interactions, including the impact of spider mite herbivory on plant growth and seed production and changes in prey population size in the presence of different predator abundances.
Quantifying genetic variation in the response to multiple stresses in plants
We studied how different plant genotypes respond to herbivory and competition. We found that herbivory reduced seed production, and this effect was more pronounced under competition. However, some plants were more affected by herbivory and others by competition, which suggests that there is genetic variation on our plant populations to respond to different environmental pressures.
Developing a model to connect system stability and fitness
Along with colleagues from the University of St. Andrews, we are developing a theoretical model that combines kin selection theory and predator-prey dynamics. We have already described how the ecosystem behaves considering only ecological dynamics and we are currently working to include evolutionary dynamics.
Predicting stability in complex ecosystems
In collaboration with colleagues from Doñana’s Biological Station and the Faculty of Sciences of Lisbon, we applied the structural stability framework to better understand how herbivore competition and evolution shapes coexistence between species. In a step further, our aim is to apply this framework to our tri-trophic system. This will help us predict the long-term stability of our ecosystem, without needing to rely heavily on temporal experimental data.
So far DYNAMICTRIO has produced two major achievements. The system that we developed to maintain our tri-trophic system can be used in other experimental evolution systems to encompass studies using more complex systems with plants and small invertebrates. Results from this project have also contributed to further our knowledge on how evolution in response to stressful environments (such as pollution) can shape coexistence between competing species.
- The "ecosystem in a box" model that we developed to harbour our ecosystems could be used in the future to study even more complex ecosystems. For example, it could be used understand how the soil microbiome is affected by the above-ground eco-evolutionary dynamics and can in turn affect those eco-evolutionary.
- To determine how to predict stability in our tri-trophic system, i.e. in more complex ecosystems, we started by applying the structural stability framework to simpler systems, with two interacting species. In collaboration with colleagues from the Faculty of Sciences of Lisbon and from the Doñana Biological Station we studied how two species of spider mites adapt to an environment with high levels of cadmium, a toxic metal. This is important because we often do not know much about how environmental changes, like pollution, affect the way species interact and live together over time. With our study, we found that when these spider mites evolved in a cadmium-rich environment, their growth rates changed, as well as how they competed. Interestingly, the two species could coexist in this new environment, but only after they both adapted to the stress of the pollution. This is an important result, because it shows that even in the absence of other species, environmental stressors like pollution can influence how species evolve and whether they can live together in the long term. This challenges the common belief that species can only coexist when they evolve in response to each other, not considering the role that environmental factors like pollution can play in shaping these interactions.
- The "ecosystem in a box" model that we developed to harbour our ecosystems could be used in the future to study even more complex ecosystems. For example, it could be used understand how the soil microbiome is affected by the above-ground eco-evolutionary dynamics and can in turn affect those eco-evolutionary.
- To determine how to predict stability in our tri-trophic system, i.e. in more complex ecosystems, we started by applying the structural stability framework to simpler systems, with two interacting species. In collaboration with colleagues from the Faculty of Sciences of Lisbon and from the Doñana Biological Station we studied how two species of spider mites adapt to an environment with high levels of cadmium, a toxic metal. This is important because we often do not know much about how environmental changes, like pollution, affect the way species interact and live together over time. With our study, we found that when these spider mites evolved in a cadmium-rich environment, their growth rates changed, as well as how they competed. Interestingly, the two species could coexist in this new environment, but only after they both adapted to the stress of the pollution. This is an important result, because it shows that even in the absence of other species, environmental stressors like pollution can influence how species evolve and whether they can live together in the long term. This challenges the common belief that species can only coexist when they evolve in response to each other, not considering the role that environmental factors like pollution can play in shaping these interactions.