11. Diversity vs., Stability

Question 1

Structure of the lecture

Answer 1

1. Biodiversity is complex and multifaceted
2. Stability is comprised of resistance and resilience
3. Does diversity beget stability?
4. Productivity vs., stability?
5. Resolving the debate

Question 2

Define diversity

1.1

Answer 2

Purvis and Hector, 2000, defined diversity as a function of species richness and species evenness, and requires many equally distributed species

Question 3

How is defining diversity complex?

1.2

Answer 3

Neem et al., 2012
Biodiversity is complex and multifaceted. It occurs on many levels, ranging from phylogenetic to taxonomic, genetic and functional.
There is a lack of well written studies on phylogenetic and taxonomic diversity

Question 4

What is stability?

2.1

Answer 4

Stability is a function of resistance and resilience (/recovery), which work to define long-term stability over time

Question 5

Argument 1: Diversity leads to stability

3.1

Answer 5

Odum, 1953
MacArthur, 1955
Elton, 1958

The more diverse, the more stable

Diverse communities have more alternative routes for energy flow, and more negative feedback loops to control breakout, and more species redundancy

Question 6

Argument 2: Diversity decreases stability

3.2

Answer 6

May,1970

The more diverse, the less stable

Perturbations are more likely to propagate further in food webs with more species and greater connectivity

Question 7

What is the Insurance effect?

3.3

Answer 7

Biodiversity provides an insurance againt perturbations , so long as species respond in different ways to buffer the ecosystem level response

Loreau et al., 2021

Question 8

What is the Portfolio effect?

3.4

Answer 8

The benefit of biodiversity due to statistical averaging in the long run

Tilman et al., 2014

Question 9

How does biomass production change in fluctuating communities?

4.1

Answer 9

Total biomass production over time is more stable when species populations fluctuate asynchronously.

Ecosystems with lower species abundance have more stable populations, but less stable productivity

Ecosystems with higher species abundance have less stable populations, but more stable productivity

Question 10

How did Tilman test for productivity vs., stability?

4.2

Answer 10

Tilman, 2006

Tested and quantified temporal stability using experimental grassland communities sest up with monocultures and diverse mixtures. Found that diverse ecosystems are more stable.

Question 11

How were debates between diversity and stability resolved?

5.1

Answer 11

Stability and complexity depend on the level at which we look at a population. Concentrating on a particular level or species gives an impression of flux and hazard. Concentrating on total community patterns shows stability, steadiness and patterns

Question 12

Open questions surrounding diversity and stability?

Answer 12

1. Linking stability concepts in economics and ecology
2. Understanding resilience and resistance
3. Understanding trade-off between maximising productivity over time