Joseph Connell

Background on Ecological Observations
- In the 1960s, researcher Joseph Connell studied rocky shorelines, observing how different sea creatures lived in specific areas when the tide went out.
- He noted that certain types of organisms were found at different heights along the shore, each with unique colors and textures.

Identified Species
  - At a certain height above where the water goes down to at low tide, a barnacle called Chthamalus stellatus was noticed.
  - Lower down, another barnacle named Semibalanus balanoides was seen.
  - Each species lives at specific heights along the shore.
Experiment on Removal of Barnacle Species
  - Connell wondered what would happen if he removed one of the barnacle types from their habitat.
  - He first removed the Semibalanus balanoides barnacle.
  - Result: The Chthamalus stellatus barnacle moved down to fill the spot left by Semibalanus.
  - Connell then removed the Chthamalus stellatus barnacle.
  - Result: The Semibalanus balanoides did not move up to occupy the higher spot left empty, likely because it cannot survive in such dry conditions.
  - This led to questions about how these species interact with each other in the environment.

Low Tide Dynamics
- When the tide is high, sea creatures are surrounded by water; at low tide, they are left out in the air.
- Different organisms can handle exposure to air and water in various ways.
Inferences from the Experiment
  - If Semibalanus balanoides is removed, Chthamalus stellatus can take its place.
  - If Chthamalus stellatus is removed, Semibalanus balanoides does not move up, possibly due to its sensitivity to drying out.
  - This led to ideas about competition for living space:
   - Chthamalus could survive deeper down but doesn't due to competition from Semibalanus.
  - Semibalanus remains where it is due to its inability to go higher up when it gets too dry.

Definition of Ecological Niche
  - An ecological niche is like a job or role a species has in its environment, including how it interacts with other living things (biotic) and non-living things (abiotic).
  - There are two types of niches:
   - Fundamental Niche: What a species is capable of doing.
   - Realized Niche: What the species actually does in reality.
   - Example from the barnacle study:
   - Chthamalus stellatus can survive higher up than it usually lives, but competition keeps it from expanding there.
   - Semibalanus balanoides lives at its full potential zone since it does not compete for higher areas.

Task: Sketch out the potential (fundamental) and actual (realized) niches for each barnacle species using dotted lines for potential and solid lines for actual niches.

Interaction and Overlap
  - Sometimes species can share space, which can lead to competition for resources.   - If two species overlap a lot, one may push the other out (this is called competitive displacement).
  - Example: The Red Fox outcompetes the Arctic Fox in areas they both live.
  - Competition can be:
  - Interference Competition: One species directly prevents another from getting resources.
  - Exploitation Competition: One species uses a resource so much that others cannot use it.

Definition: Splitting resources among species helps minimize competition.
- Example: Anolis lizards in the Caribbean choose different heights to sit on branches to avoid competing with one another.
- Temporal Resource Partitioning: Dividing based on active times (like daytime vs. nighttime) to reduce overlap.

Niche Breadth
- Generalist species use a variety of resources, which can make them less efficient overall (e.g., Red fox).
- Specialist species thrive on specific resources and do better (e.g., Texas horned lizard that mainly eats harvester ants).
Community Insights
- In areas with many species, niches are often narrow and specialized to reduce competition.
- Biodiverse places like coral reefs have many specialists that are more at risk if their resources decrease.

Predation Impact: How predators shape community structure is vital for understanding ecological diversity.
  - An example is an experiment by Robert Payne involving Pisaster sea stars, predators in intertidal zones.
  - When these predators were removed, there was a significant decrease in species diversity.
  - Key Concept: Keystone species like predators are crucial for maintaining community diversity; their removal can decrease species variety.
  - Predators help keep balance by managing the number of prey, which fosters more biodiversity.

Classification of Interactions:
  - Competition: Bad for both species.
  - Predation: Good for the predator, bad for the prey.
  - Parasitism: Good for the parasite, bad for the host.
  - Herbivory: Good for the herbivore, bad for the plant.
  - Mutualism: Good for both species involved.
  - Commensalism: One benefits, the other is unaffected.
Conclusion: Understanding these interactions is essential for ecological studies and conservation efforts.