Modeling the assembly and disassembly of complex ecological systems | 9am PT Tues, March 4, 2025

[Grigory Bronevetsky]

Modeling Talks

Modeling the assembly and disassembly of complex ecological systems Dr Miguel Lurgi, Swansea University Tues, March 4, 2025 | 9am PT Meet | Youtube Stream Hi all, The presentation will be via Meet and all questions will be addressed there. If you cannot attend live, the event will be recorded and can be found afterward at https://sites.google.com/modelingtalks.org/entry/modelling-the-assembly-and-disassembly-of-complex-ecological-systems More information on previous and future talks: https://sites.google.com/modelingtalks.org/entry/home Abstract: Understanding the factors that influence the persistence and stability of complex ecological networks is a central focus of ecology. Research into these factors has attempted to unveil the ecological processes and network structural constraints modulating ecosystem stability using modeling approaches. Mechanistic models of community assembly in turn play a fundamental role in obtaining a better understanding of the potential effects of different aspects of global change, such as habitat loss, warming, and invasions, on complex ecosystems. In parallel, attention has also been given to understanding the consequences of evolution within complex ecological settings, as the interplay between ecology and evolution has been recognised as fundamental to understand the formation of ecological communities. The development of eco-evolutionary theory and models would ultimately allow us to obtain a comprehensive understanding of the drivers of assembly and disassembly of natural communities. In this talk I will present a few modeling approaches we have developed over the last few years to better understand the drivers of assembly in species interactions networks. Using a spatially-explicit, individual-based model we explored how spatial dynamics and a mixture of interaction types affect the stability of complex food webs. This model is then put into practice to investigate the effects of habitat loss and fragmentation on the composition and stability of food webs. Our results show how different types of habitat loss affect ecosystem stability in different ways. These effects are mediated by changes in the strength of interactions between species. Switching to a mean-field approach to community dynamics, I will present our findings on how the synergistic effects of increases in temperature and invasions impact the structure and stability of complex food webs. In the last part of the talk, I will extend this type of network dynamics model into the evolutionary realm. Using a mutualistic population dynamical model incorporating evolutionary adaptation events, we relate ecological aspects of mutualistic community stability to the stability of evolutionary pathways that allow their persistence. This research illustrates the pivotal role of dynamical modeling in obtaining a better understanding of ecological community assembly and in developing tools to predict the potential effects of anthropogenic environmental change on complex ecosystems.   Bio: Miguel obtained his PhD in Terrestrial Ecology from the Autonomous University of Barcelona in 2014. He developed his doctoral research jointly at the Marine Sciences Institute (ICM-CSIC) and the Centre for Ecological Research and Forestry Applications (CREAF). After his PhD, Miguel completed his postdoctoral training at the University of Adelaide, Australia (2014-2016) and the Theoretical and Experimental Ecology Station of the CNRS, France (2016-2019). Since 2019 he leads the Computational Ecology Lab at Swansea University, UK where he is an Associate Professor. Miguel is interested in obtaining a better understanding of the ecological and evolutionary mechanisms behind the assembly of complex species interaction networks across spatial scales and ecosystem types. Further, he is interested in applying this knowledge to understand the impacts of different aspects of global change on complex ecosystems. To tackle these challenges, he studies a variety of systems at various scales, from microbial communities to continent-wide food webs. His research combines analyses of complex datasets of species distributions and interactions with the development of theoretical models of community assembly incorporating ecological and evolutionary processes. This approach ultimately seeks to contribute to the mechanistic understanding of large-scale biodiversity patterns and how they break in the face of environmental perturbations.

[Grigory Bronevetsky]

Video Recording: https://youtube.com/live/nc2jPNKW7C8

Slides: https://drive.google.com/file/d/15mpmc_jhcQUBvrNlOt9ksbEz8q6HRZUl/view?usp=sharing

Summary:

• Goal: model dynamics of ecological systems

  • Community assembly and disassembly

  • Drivers: warming, extinctions, invasions, over-exploitation

  • Approach: mixed approach of theoretical models and computational ecology

    • Differential equations

    • Network analysis

    • Spatial dynamics

    • Empirical data analysis

• Aims:

  • Understanding the effects of space and mixture of interaction types on complex interaction networks and their disassembly

  • Impact on food webs?

  • Impacts of habitat loss?

  • Approach: simulation of interaction webs

• Interaction types and community stability

  • Mutualistic interactions: benefit both entities (vs antagonistic)

  • Adding mutualistic interactions 

    • Improves total community abundance, 

    • Reduces quantitative generality (number of interaction partners each species has)

      • More mutualistic: stronger interactions with a few partners

      • More antagonistic: many weak interactions

  • Impact of habitat loss:

    • Feeding and mutualistic interaction networks

    • Stability decreases with habitat loss through its effect on interaction strengths

    • Losing a large amount of habitat significantly affects migration, with more random loss patterns causing individuals to migrate less because the paths connecting different regions become much longer and windier

• Synergistic effects of invasions and warming on food webs

  • Model: 

    • Differential equation that relates the rate of species growth and biomass loss

    • Separate components for species at different trophic levels (role in the food web as predators or prey)

  • Compare simulations before/after invasions

    • Species that can invade successfully have more connections and more food chains

    • Higher connectivity of food web network makes entire food webs more resilient to invasions (more different species have similar roles) but makes individual species more vulnerable (more food interactions to change/break)

  • Synergistic effects of invasions and warming

    • Temperature affects species depending on their body sizes

      • E.g.: small animals have faster metabolism, will be heavily accelerated by warming temperatures

    • Warmer networks lost more species and interactions

    • Invasions more impactful when cold ecosystems are warmed, rather than already warm ecosystems being warmed further

• Linking ecological and evolutionary stability on the assembly of mutualistic networks

  • Selection - competition - evolution - biodiversity

  • Model of species interactions between plants and their pollinators

    • Intra-level competition (pollinators-pollinators and plants-plants)

    • Inter-level mutualism (plants-pollinators)

  • Applied random mutations to links between species: swap, loss, creation of links

  • Varied levels of competition among species and each species growth

  • Networks that were most robust to perturbation will be resilient at a longer evolutionary time frames because they keep adapting via evolution