Question

Sparrows use two foraging tactics to obtain food. They either search for grains themselves (Producer tactic P) or follow other individuals and steal grains from them (Scrounger tactic S). The following graphs show how the fitness of each tactic (P : dashed line and S : solid line) varies as a function of the relative frequency of S. Which one of the graphs shows the correct representation of these tactics if they were maintained through negative frequency dependence?

• A. A
• B. B
• C. C
• D. D

Hint:

In negative frequency-dependent selection, the fitness of a trait decreases as it becomes more common, while rarer traits are favored.

Answer 1

The Correct Option is C

Step 1: Understand the concept of negative frequency dependence.
In negative frequency-dependent selection, the fitness of a strategy decreases as it becomes more common. This is because rarer strategies have a fitness advantage since they can exploit more common strategies.
Step 2: Analyze the options.
- (A) The graph shows both tactics increasing as the frequency of S increases, which is not consistent with negative frequency dependence.
- (B) The graph shows both tactics decreasing, which is also not a characteristic of negative frequency dependence.
- (C) The correct graph shows the fitness of the producer tactic (P) decreasing as S becomes more common, while the fitness of the scrounger tactic (S) increases as it becomes more rare. This is characteristic of negative frequency dependence.
- (D) This graph shows no variation in fitness, which doesn’t reflect any form of frequency dependence.
Step 3: Conclusion.
The graph in option (C) correctly depicts the behavior of both tactics under negative frequency dependence.