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Difficulty: HardCommand of Evidence: Textual

In a study of the cooperatively breeding cichlid fish *Neolamprologus pulcher*, evolutionary biologist Dr. Marcus Vance investigated the "pay-to-stay" hypothesis. This hypothesis suggests that subordinate helpers assist in territory defense and offspring care not solely due to kin selection, but as a form of "rent" to prevent dominant breeders from expelling them from the safety of the territory. Vance argued that if helping is indeed a transaction to secure territory residency, dominant breeders should respond to a helper's temporary inactivity with increased social policing (aggression) only when resources are scarce, as the cost of hosting a non-productive helper is higher under these conditions.

Which finding, if true, would most directly support Vance's argument?

  1. In experimental trials where subordinate helpers were prevented from assisting in territory defense, dominant breeders directed significantly more aggressive behaviors toward the inactive subordinates in resource-scarce environments than they did in resource-abundant environments.Answer
  2. B
    Subordinate helpers in resource-scarce environments performed significantly more defensive behaviors on average than did subordinate helpers in resource-abundant environments.
  3. C
    Dominant breeders in resource-abundant environments exhibited high levels of aggression toward all subordinate helpers, regardless of whether those helpers actively participated in nest defense.
  4. D
    Unrelated subordinate helpers were expelled from territories at similar rates as closely related subordinate helpers when both groups failed to assist in offspring care.

Answer

In experimental trials where subordinate helpers were prevented from assisting in territory defense, dominant breeders directed significantly more aggressive behaviors toward the inactive subordinates in resource-scarce environments than they did in resource-abundant environments.
The correct answer directly supports the hypothesis by showing that when helpers are prevented from helping, dominant breeders increase social policing (aggression) only in resource-scarce environments. This matches the prediction that such policing is conditional on resource scarcity making hosting non-productive helpers costly.

Step-by-Step Solution

1
Identify the central claim in the passage that needs support.
The claim is that dominant breeders police (show aggression toward) inactive helpers only when resources are scarce because the cost of hosting a non-productive helper increases in resource-poor conditions.
Knowing the specific claim is necessary to evaluate which evidence directly supports it.
2
Evaluate the options to find one that links dominant aggression (social policing), helper inactivity, and resource scarcity in the hypothesized way.
The correct finding must show that when helpers are inactive, dominants increase aggression specifically in resource-scarce environments compared to resource-abundant ones.
This establishes the resource-dependent policing of helper inactivity predicted by the hypothesis.
3
Rule out distractors that focus on unrelated behaviors, contradict the hypothesis, or address unrelated variables such as kin relatedness.
Findings about helper defensive behavior rates, general aggression in resource-abundant settings, or relatedness do not support the specific conditional policing hypothesis.
Eliminating irrelevant or contradictory choices confirms the correct option.

Key Concept

Command of Evidence: Textual
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Command of Evidence: Textual

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