Lecture 18 - Biodiversity

Question 1

What are the three levels of biodiversity?

Answer 1

1. Ecosystem diversity
2. Species diversity
3. Genetic diversity

Question 2

Define Genetic diversity and Evolutionary rescue.

Answer 2

Genetic diversity: The basis of evolutionary rescue

Evolutionary rescue: process by which it can save a species from going extinct.
Population declining, but some individuals in the pool have enough genetic variation so that they can do better in that environment. They reproduce, and save the species.

Question 3

Define 3 types of genetic diversity types.

Answer 3

1. Standing genetic variation (there was enough standing genetic diversity in that population to bring the size back up),
2. New individuals or
3. Mutations.

Question 4

What’s the benefit of species diversity? Name 2 Heuristics to define species diversity.

Answer 4

Makes an ecosystem more resilient.

Diversity of a community is typically reported either as richness or a diversity index that summarizes this heterogeneity.

Richness: # of species
Heterogeneity: higher if more species, and if species are more equal in abundance. (relative abundance)

Question 5

In nearly every community in which species have been identified, there are few common species and many rare species.
Name 2 hypotheses that explain this pattern.

Answer 5

1. Random expectation
2. Often similar to a pattern (log-normal) that one gets if resource niche space were divided up sequentially, rather than all at once.

Question 6

What are the 3 scales of biodiversity?

Answer 6

1. 𝛼 Alpha: how many species are in a local area. Can’t tell how unique the species are or how heterogene the environment is, which is why we need beta diversity.
2. 𝛽 Beta: difference between localities. How things change across space. How many species not shared.
   𝛽 = (𝛼1-c) +(𝛼2 - c) where c: shared species
3. 𝛾 Gamma: How many species are there in the whole region im interested in.

Question 7

Give 3 reasons why some regions have more species than others.

Answer 7

1. Evolutionary speed (2 hypothesis):
   a) evolution happens faster in warmer places. Doesn’t mean you’re gonna get more species.
   (latitudinal gradient diversity)
   b) Some regions have had less time in relatively unchanged conditions to accumulate species.
2. Geographic area: larger areas (has more niche space) support more species than smaller areas. Area alone can’t explain the distribution.
3. Ambient energy: Areas with greater energy can support more species. More energy → greater species richness in trees and vertebrates.

Question 8

Define Evapotranspiration

Answer 8

Evapotranspiration measures the energy at a site calculated from solar radiation and temperature (using the energy available to draw water into the atmosphere)

Question 9

Define horizontal diversity. Why is it important (2 hypotheses)?

Answer 9

Horizontal diversity: All the species that are using the same resources.

Hypothesized importance of horizontal diversity:

1. Having more species improve ecosystem function by increasing productivity, biomass, decomposition. With more species, these functions happen faster.
2. More disease resistance and stable.

Question 10

What was the outcome of the Cedar Creek experiment?

Answer 10

Cedar Creek experiment: Giant plot of lands (147) → How does the # of species affect that plot.
24 species total.
Measured productivity after 2 years (% cover)

Conclusion: More species led to more biomass.

Question 11

Define rivet redundancy in biodiversity

Answer 11

The idea that you can take a few species out of the ecosystem and everything will be fine, but at some point everything will collapse in productivity. (just like taking rivets out of a plane).

Question 12

Define immediate catastrophe in biodiversity

Answer 12

If you take out one species, the community collapse.