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

Dispersal means an animal leaving the area where it was born to settle somewhere else. For any behaviour to be favoured by evolution it has to give a net fitness advantage, so this question is really asking us to sort the four listed outcomes into "helps fitness" versus "hurts fitness" or "unrelated benefit".

1. Reduced competition with kin: Staying home means competing with siblings and parents for the same limited food and mates. Leaving removes that competition, which is a clear fitness gain, so this is a genuine benefit.
2. Increased predation risk outside natal areas: This is a downside of moving through unfamiliar or exposed terrain, not a benefit. It works against dispersal evolving, so it does not belong in the list of benefits.
3. Inbreeding avoidance: Relatives living close together risk mating with each other, and inbred offspring often have lower survival. Dispersing away from the natal group lowers this risk, which is a real fitness benefit.
4. Outbreeding avoidance: This means avoiding mates that are too genetically different, which is actually the opposite pressure to what dispersal usually solves. Dispersal tends to increase mixing with less related individuals, so it does not serve outbreeding avoidance.

Putting it together, only reduced kin competition and inbreeding avoidance are true benefits that would push dispersal to evolve, while increased predation risk is a cost and outbreeding avoidance is not what dispersal achieves.

Let's summarize:

• A trait spreads only if it raises average fitness, so we must separate real benefits from costs.
• Reduced kin competition and inbreeding avoidance are the two classic, textbook benefits of natal dispersal.

So the correct options are (A) and (C).