Stability and Dynamics of Resource Consumer Ecosystems
Natural ecosystems, ranging from microbiomes to forests, significantly influence humanity by affecting individual health and promoting the sustainable growth of whole society. Understanding the collective properties like diversity, stability, and diversity-stability relationships of a large complex...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Published: |
Massachusetts Institute of Technology
2024
|
| Online Access: | https://hdl.handle.net/1721.1/155901 https://orcid.org/0000-0003-2105-0894 |
| Summary: | Natural ecosystems, ranging from microbiomes to forests, significantly influence humanity by affecting individual health and promoting the sustainable growth of whole society. Understanding the collective properties like diversity, stability, and diversity-stability relationships of a large complex ecosystem having real-world structures has been a significant challenge, yet is important for better ecosystem management. In this thesis, we investigate stability and dynamics of resource-consumer ecosystems (ecosystems with two trophic levels). Beginning with geometric analyses of small systems, we uncovered a critical instability arising from a mismatch between resources that promote growth (defined as niches) and those predominantly consumed. This instability emerges when the discrepancy between consumption and growth exceeds the differences among nearest niches, indicating that species are more likely to encroach upon the niches of others rather than their own. After losing stability, the extent to which species encroach upon their neighbors’ niches can predict the diversity and sizes of attractor basins. We further develop a stability criterion with statistical properties of consumption and growth, employing random matrix theory. This criterion hinges on the correlation between growth-promoting resources and those primarily consumed, with the critical level of discrepancy being influenced by the ratio of species to resources. This result is consistent with the geometric interpretation, giving an analytic estimation of maximum niche overlaps. Additionally, we uncover fundamental symmetries in system stability, enhancing our stability criterion through geometric insights and extending its applicability to realistic situations. Later, by integrating mechanisms such as cross-feeding, toxin production, species autoregulation, etc., our expanded model framework accommodates scenarios where consumers outnumber resources, thereby refining our stability criterion. Notably, we identified a re-entrant stability phenomenon, where increased diversity within trophic levels initially destabilizes but subsequently stabilizes the community. This leads to the conclusion that the difference in diversity between trophic levels is crucial for ecosystem stability, with the least stable ecosystems being those with comparable numbers of species across levels. Our work establishes a mechanistic understanding of ecosystem instability through niche encroachment and shows that stability hinges on diversity differences across trophic levels rather than total diversity, therefore emphasizing the significance of mechanistic structures in predicting large ecosystem behaviors. |
|---|