SEE-U 2000: Atlantic Forest - Lecture

## Lecture Archive

## Natural Selection, Evolution, and Evolutionary Ecology
Presenter: James Danoff-Burg

### Natural Selection, Evolution, and Evolutionary Ecology

James Danoff-Burg
Columbia University

## Black Rock Forest, New York

### Levels of Ecological Explanation

- Ultimate
  - Evolutionary influences
- Proximate
  - Human influences
  - Abiotic changes
  - Biotic interactions

Most ecologists explore the last three levels

### Progress of Ecological Inquiry?

- Explore plausible ultimate answers
- If one is supported, stop
- If no ultimate answers are supported, explore proximate answers

### Rationale

- Need to pitch the question at the right level
- Example:
  - Why are Penguins only in the Southern Hemisphere?
  - Proximate - insufficient food, too many predators, lack of shelter, etc.
  - Ultimate - historical and thus evolutionary distribution --> favored at present

### Two EvolEcol Branches

- Intraspecific
  - Relative selective value of different traits
  - Origin of intraspecific diversity
- Interspecific
  - Behavioral ecology (comparative studies)
  - Systematics and phylogeny

Common feature of all branches - Evolution!

### Evolution

- Change through time within a lineage
- Mechanisms / Producers of Variation
  - Genetic drift
  - Phenotypic plasticity
  - Natural Selection

Natural Selection is not equal to Evolution

### Natural Selection

- Proposed by Darwin and Wallace
- Evolutionary mechanism
- One way that variation exists and is maintained in a population
- Value is relative to local competitors
- Only a negative action
  - Only selection AGAINST a form of a trait
  - Never selection for a trait

### Intraspecific Variation

- Possible sources:
  - Genetic drift
  - Phenotypic plasticity
  - Natural Selection
- How to differentiate between them?
  - Genetic fixation / continuity through lineages
  - Use traits that do not change in response to changes in environment

### Today's Activity

- How do changes in a resource gradient affect intraspecific diversity?
  - Are these changes due to natural selection?
- Choose an organism with the following characteristics:
  - Low vagility
  - Does not disperse aerially
  - Clearly marked adult stage
  - Traits under study do not change

### Activity Tasks

- Plan activity
- Collect data and enter into eBiome
- Analyze our data
- Wait for data from other sites
- Jointly analyze all data
- Make conclusions about relationship
- Posit future studies to distinguish between evolutionary mechanisms

### Planning - To be Determined:

- Environmental variable
- Experimental organism
- Organismal trait for study
- Statistical technique to use, justify