51³Ô¹Ï

Topic

Co-evolution of ecosystems and their environments: modeling the evolution of ecosystem-level responses to, and impacts on, environmental temperature

School of Earth and Ocean Sciences

Date & location

• Monday, June 9, 2025
• 9:00 A.M.
• Clearihue Building, Room B017

Examining Committee

Supervisory Committee

• Dr. Colin Goldblatt, School of Earth and Ocean Sciences, 51³Ô¹Ï (Co-Supervisor)
• Dr. Rana El-Sabaawi, Department of Biology, UVic (Co-Supervisor)
• Dr. Jay Cullen, School of Earth and Ocean Sciences, UVic (Member)
• Dr. Mark Lewis, Department of Biology, UVic (Outside Member)

External Examiner

• Dr. Rudy Arthur, Department of Computer Science, University of Exeter

Chair of Oral Examination

• Dr. Tim Hopper, School of Exercise Science, Physical and Health Education, UVic

Abstract

Over the course of the history of life on Earth, major changes in both the environment and the biota have occurred. Organisms have both adapted to the physical and biological components of their surroundings, and also affected them. Many species alive today engage in niche construction: their modifications to the environment feedback on their own evolution. Some species also affect the evolutionary pressures experienced by others. However, while organisms are known to affect both the environment and the evolution of their own and other species, a general understanding of how organismal impacts on the environment evolve, and how these impacts feedback on ecosystem characteristics, is still lacking. This is necessary for understanding Earth system evolution and the pressures that drive the evolution of macroecological patterns.

In this dissertation, I modify a model of ecology and evolution called the Tangled Nature (TaNa) model to investigate ecosystem-level responses to and impacts on temperature. I first characterize how ecosystem properties depend on temperature, and find that ecosystem survival probability, species richness, and ecological interaction strengths are strongly temperature dependent. The probability of ecosystems surviving depends on the ratio between birth and death rates, and species richness and interaction strengths depend on mutation rate.

Next, I couple the TaNa+T with a climate model and enable organisms to increase or reduce atmospheric carbon, thus affecting the climate, in the Tangled Nature + Climate (TaNC) model. I demonstrate and characterize ecosystem-level niche construction, showing that ecosystems in the TaNC evolve toward cooler temperatures where death rates are reduced, and this can feedback on, and reduce, species richness and abundance.

I then test the sensitivity of the TaNC to assumptions about how species respond to and affect the environment. I find that species with similar thermal optima of reproduction do not modify the climate to maximize reproduction. Instead, minimizing death rates guides the evolution of ecological impacts on the environment.

Finally, I probe into ecosystem-level inheritance by making species’ responses to and impacts on the environment heritable during speciation. Inheritance of species-environment interactions increases ecosystem extinction probability, but surviving ecosystems acquire larger species richness and abundance when thermal optima of reproduction are heritable.

Overall, this work illustrates general properties of ecosystem-environment coevolution, making an important contribution to the fields of Earth science and eco-evolutionary feedbacks. This also provides a tool that can be used in future research.