Q5: Biodiversity and ecosystem function

Question 1

What is biodiversity?

Answer 1

Biodiversity is the variety and variation of life in a given area

Question 2

What is ecosystem function?

Answer 2

Ecosystem function is the aggregation of processes that occur in a given ecosystem, including energy flows into and out of the system, productivity and population dynamics of its species, the processes that structure its communities and the ability to resist minor disturbance

Question 3

What are the primary mechanisms hypothesized to explain how biodiversity could promote ecosystem function?

Answer 3

Sampling effects, complementarity, and portfolio effects

Question 4

What is the sampling effects hypothesis?

Answer 4

From a probabilistic perspective, the more species there are, the greater the likelihood that one will be able to perform a given function well.

Question 5

What is the complimentarity hypothesis?

Answer 5

Different species may use resources in different ways, thereby being able to extract and transfer more resources than a smaller number of species

Question 6

What is the portfolio effect?

Answer 6

Is a metaphor of a diverse stock portfolio that minimizes the risk of large losses. This mechanism assumes that variation in an environment and a species’ differential ability to exploit it averages out over time.

Question 7

What is the evidence from experiments in terrestrial and marine communities?

Answer 7

A meta-analysis by Worm et al. (2006) in Science of the effect of genetic and species richness on key marine ecosystem functions like primary production, nutrient cycling and ecosystem stability found that diversity significantly increased each of these functions. Another meta-analysis by Balvanera and others (2006) of mostly terrestrial systems assessed experimental evidence for the relationship between many ecosystem processes and diversity and found a significant and positive relationship overall.

Question 8

How does diversity relate to resistance?

Answer 8

By buffering the effects of a disturbance. In a diverse community, different species would respond to the disturbance differently, and therefore the disturbance would be distributed across many species, reducing the magnitude of impact to the whole system.

Question 9

How does diversity relate to resilience?

Answer 9

Recovery could happen faster if in a given functional group, there are more tolerant species that persist and keep functioning. If the ecosystem function returned to its pre-disturbance values quickly, presumably the species that were disturbed would be able to grow back into their niche