Which scenario best explains how a founder effect could drive divergence in armor traits in a newly established freshwater lake population?

Which scenario best explains how a founder effect could drive divergence in armor traits in a newly established freshwater lake population?

• A. A large founding population may carry more diversity thus accelerate divergence.
• B. Gene flow from marine populations is high, reducing divergence.
• C. Founder effects cannot influence armor traits.
• D. A small founding population may carry non-representative alleles; genetic drift can fix unusual armor phenotypes early on.

Answer: (D)

The main idea here is that a founder effect can cause rapid changes in a small new population because the alleles they carry may not reflect the original population. When only a few individuals colonize a freshwater lake, their genes set the starting frequencies for armor traits. If those founders happen to carry unusual or non-representative armor alleles, genetic drift can quickly fix those alleles in the new population, leading to divergence from the source population. This explains how armor phenotypes can shift early on simply by chance in a small group. The other scenarios don’t fit as well. A large founding population reduces the randomness of allele sampling, so it’s less likely to diverge quickly. High gene flow from marine populations would keep the lake population genetically similar to the marine source, counteracting divergence. And founder effects can indeed influence armor traits because these are genetic traits that can be affected by which alleles happen to be present in the founding individuals.

The main idea here is that a founder effect can cause rapid changes in a small new population because the alleles they carry may not reflect the original population. When only a few individuals colonize a freshwater lake, their genes set the starting frequencies for armor traits. If those founders happen to carry unusual or non-representative armor alleles, genetic drift can quickly fix those alleles in the new population, leading to divergence from the source population. This explains how armor phenotypes can shift early on simply by chance in a small group.

The other scenarios don’t fit as well. A large founding population reduces the randomness of allele sampling, so it’s less likely to diverge quickly. High gene flow from marine populations would keep the lake population genetically similar to the marine source, counteracting divergence. And founder effects can indeed influence armor traits because these are genetic traits that can be affected by which alleles happen to be present in the founding individuals.