Question

Which one or more of the following benefits can explain the evolution of dispersal of animals from their natal area?

• A. Reduced competition with kin
• B. Increased predation risk outside natal areas
• C. Inbreeding avoidance
• D. Outbreeding avoidance

Hint:

A benefit must raise fitness. Ask which options describe a cost of moving away rather than a genuine advantage, and which describe the wrong direction of avoidance.

Answer 1

The Correct Option is A, C

Step 1: Understanding the Question.
Natal dispersal is the movement of an individual away from the place where it was born, to settle and possibly reproduce elsewhere. The question asks which of the four listed outcomes count as a real benefit that could have driven the evolution of this behaviour.

Step 2: Key Concept.
For a behaviour like dispersal to evolve and persist, it must, on average, raise the fitness of the individuals that disperse compared with those that stay. Biologists usually explain the evolution of dispersal through three main benefits: it reduces competition for resources and mates with close relatives, it lowers the chance of inbreeding with relatives, and it can also let individuals find better quality habitat. We check each option against this idea of a genuine fitness benefit.

Step 3: Detailed Explanation.
Option (A): Reduced competition with kin. If an individual stays in its natal area, it competes with siblings and parents for food, territory and mates. By dispersing, it escapes this local competition, which is a genuine benefit, so (A) is correct.
Option (B): Increased predation risk outside natal areas. This describes a cost of dispersing, not a benefit, since dispersing animals often face unfamiliar terrain and higher exposure to predators while moving. A cost cannot be the reason dispersal evolved, so (B) is not correct.
Option (C): Inbreeding avoidance. Staying in the natal group raises the chance of mating with a close relative, which can produce inbred, less fit offspring. Moving away from the natal area reduces the chance of meeting and mating with relatives, so this is a real benefit, and (C) is correct.
Option (D): Outbreeding avoidance. Outbreeding avoidance refers to avoiding mating with genetically too-distant individuals, which is the opposite concern from what dispersal usually helps with. Dispersal actually increases the chance of mating with less related individuals, so it works against outbreeding avoidance rather than promoting it, making (D) incorrect.

Step 4: Final Answer.
The genuine benefits of dispersal from the given list are reduced kin competition and inbreeding avoidance, so options (A) and (C) are correct.
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