1 / 21

Exploring Diversity and Stability Relationship in Ecosystems

This study delves into the intricate balance between diversity and stability in ecosystems. It analyzes how increased species diversity impacts ecosystem stability, examining concepts from MacArthur to May. By exploring mathematical models, ecological implications, and experimental results, it aims to reconcile conflicting theories and shed light on the complex interactions within ecosystems.

jkilgore
Download Presentation

Exploring Diversity and Stability Relationship in Ecosystems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Diversity and Stability By Ariana Strandburg-Peshkin

  2. Does Increased Diversity Lead to Increased Stability?

  3. What is stability? - MacArthur • Abundances of species staying relatively constant • Perturb one species --> Others relatively unaffected • The amount of choice which the energy has in following paths up through the food web

  4. Complexity & Stability - MacArthur It’s Intuitive! VS.

  5. Implications of MacArthur’s Stability Definition • Stability can be increased by… • Increasing the number of links • Increasing the number of species • Complexity --> Stability is implied in the definition • Evolution optimizes for maximum efficiency subject to a certain necessary stability

  6. Ecological Implications, if this is true… • Small number of species --> hard to fulfill stability requirement --> must diversify diet • Large number of species --> stability requirement easily fulfilled --> can specialize

  7. Along Comes Robert May… I know math. You’re all wrong! • In mathematical models, complexity tends to lead to instability

  8. Lotka-Volterra Models - May

  9. Lotka-Volterra Models - May

  10. Mathematical Models - May • Randomly-Constructed Community Matrices • Too rich web connectance --> instability • Too large average interaction strength --> instability

  11. Tilman’s Study • Effects of Nitrogen addition to soil • 207 plots of land, 9 different nutrient treatments • Sampled biomass every year • Major droughts in 1987 and 1988

  12. Tilman - Results • Species-rich plots more drought resistant

  13. Tilman - Results • Total biomass variability (c.v.) negatively correlated with SR (both drought and non-drought)

  14. Tilman - Results • Biomass of individual species varied more in SR plots

  15. Reconciling MacArthur and May Stop arguing! You’re both right! • For COMMUNITIES - diversity --> stability • For SPECIES - diversity --> instability • But wait…

  16. How Can This Be??

  17. How can this be?? • Competitive Release / Compensatory Growth • Monocultures - Avg. response to perturbation = Avg. of individuals • Mixtures - Avg. response to perturbation includes compensatory growth • Mixtures do better --> Species-rich plots do better b/c higher probability of perturbation resistant plants

  18. What About Omnivores? • Omnivore - species that feeds on more than one trophic level • Classical Mathematical Results: Omnivory --> Instability • Fagan: Omnivory --> Stability

  19. Fagan - Experiment • Studied arthropod communities • Manipulated level of omnivory • Perturbed populations

  20. Fagan - Results • Omnivory decreases coefficient of variation after a perturbation • Probably due to rapid response of omnivores to changing pressures

  21. References • MacArthur, R.H. Fluctuations of animal populations and a measure of community stability. Ecology 36, 533-536 (1955) • May, R.M. Stability and Complexity in Model Ecosystems (Princeton Univ. Press, 1973). • Tilman, D. Biodiversity: population versus ecosystem stability. Ecology 77, 350-363 (1996). • Fagan, W.F. Omnivory as a stabilizing feaure of natural communities. Am. Nat. 150, 554-567 (1997).

More Related