How does a 'common garden' help differentiate genetic versus environmental causes of trait differences?

• A. By rearing individuals from different populations in the same environment, any persistent differences are likely genetic.
• B. By rearing individuals from different populations in different environments.
• C. By sequencing genomes to identify gene variants.
• D. By measuring environment factors in the wild.

Answer: (A)

A common garden experiment tests whether differences in a trait between populations are genetic or environmental by keeping the environment the same for all groups. By rearing individuals from different populations in the same conditions, any persistent differences in the trait point to genetic differences, since the environmental influence has been held constant. If the populations become indistinguishable in that shared environment, the differences seen in the wild were due to environment or plastic responses rather than genetics. Rearing in different environments would not separate those causes, sequencing genomes looks for gene variants without showing how they manifest in a shared environment, and measuring environmental factors in the wild doesn’t control for genetic differences.