A group of biologists is studying the competitive relationships among strains of bacteria that exist in the guts of fish. The researchers have constructed a competitive dominance hierarchy diagram for a particular set of conditions (shown below). Under these conditions, which bacterial strain is the LEAST competitively dominant?
The Correct Answer and Explanation is:
To determine the least competitively dominant bacterial strain, we need to interpret a competitive dominance hierarchy diagram. While the diagram itself is not shown in your message, such diagrams typically use arrows to indicate dominance: an arrow pointing from Strain A to Strain B suggests that A outcompetes B.
How to Analyze the Diagram:
- Count the outgoing arrows: The more arrows going out from a strain, the more dominant it is (it outcompetes others).
- Count the incoming arrows: The more arrows pointing to a strain, the less dominant it is (others outcompete it).
The least competitively dominant strain is the one with:
- The most arrows pointing to it from other strains.
- Few or no arrows pointing out to others.
Explanation (Assuming a Generic Hierarchy):
Let’s suppose the diagram includes four strains: A, B, C, and D.
- If strain D has arrows pointing to it from A, B, and C, and has no arrows pointing to others, then D is the least competitively dominant.
- This means that D gets outcompeted by every other strain under the given conditions.
Why This Matters:
In microbial ecology, understanding dominance helps researchers predict which strains will persist or decline in certain environments. A less dominant strain may:
- Struggle to obtain resources.
- Be outgrown or outcompeted.
- Only survive in niches where dominant strains are absent.
This insight can inform interventions, such as manipulating gut flora to improve fish health or resist disease. If one strain is consistently least dominant, it might be a poor candidate for probiotic use under those conditions.
In conclusion, the least competitively dominant strain is the one that is defeated by most or all others in the hierarchy. Identifying this strain involves examining the direction and number of arrows in the diagram and selecting the strain with the highest number of defeats and the fewest victories.