Which statement about standing variation and gene flow is most accurate for trait divergence across lakes?

Which statement about standing variation and gene flow is most accurate for trait divergence across lakes?

• A. Donor populations always impose the same variants across all lakes.
• B. Differences in standing variation and gene flow can yield different evolutionary trajectories.
• C. Gene flow always prevents divergence.
• D. Standing variation has no effect on adaptation.

Answer: (B)

The key idea is that how much genetic material is already ready to be acted on (standing variation) and how connected the populations are through gene flow together shape how populations diverge across lakes. If each lake has different sets of standing variants, each population starts with a different toolbox of alleles that selection can act on, leading to distinct adaptive paths. Gene flow adds or swaps alleles between lakes; it can spread beneficial variants and enable shared adaptation, but it can also dilute locally adapted alleles if migrants bring maladaptive ones. Because these two factors vary between lakes, they can produce different evolutionary trajectories rather than a single, uniform outcome. The other statements are not accurate because standing variation isn’t the same everywhere, gene flow doesn’t always stop divergence (it can either hinder or promote it depending on the context), and standing variation does influence adaptation.

The key idea is that how much genetic material is already ready to be acted on (standing variation) and how connected the populations are through gene flow together shape how populations diverge across lakes. If each lake has different sets of standing variants, each population starts with a different toolbox of alleles that selection can act on, leading to distinct adaptive paths. Gene flow adds or swaps alleles between lakes; it can spread beneficial variants and enable shared adaptation, but it can also dilute locally adapted alleles if migrants bring maladaptive ones. Because these two factors vary between lakes, they can produce different evolutionary trajectories rather than a single, uniform outcome. The other statements are not accurate because standing variation isn’t the same everywhere, gene flow doesn’t always stop divergence (it can either hinder or promote it depending on the context), and standing variation does influence adaptation.