Question

You are a plant ecologist studying a plant in the genus Veronica. You notice that, at open rocky sites, Veronica grows as a creeper spreading low to the ground, whereas in grasslands, the stem stands upright. You collect seeds from multiple populations in each habitat type and grow them under uniform conditions in a greenhouse. You find that all the plants grown in the greenhouse have stems that stand upright. Which one or more of the following explanations best support(s) your observations?

• A. The different morphologies in the natural habitat types are due to phenotypic plasticity.
• B. Inbreeding depression has led to the creeping form in the rocky sites.
• C. High gene flow between populations has restricted local adaptation in the two environments.
• D. The morphological differences between populations demonstrates that growth form is a polygenic trait.

Hint:

If different phenotypes disappear when organisms are raised in a common environment, the variation is most likely due to {phenotypic plasticity}, not genetic differentiation.

Answer 1

The Correct Option is A

Step 1: Interpret the key observation.
Plants from both rocky sites and grasslands were grown under identical greenhouse conditions.
Despite their different growth forms in nature, all plants developed upright stems in the greenhouse.
This indicates that the observed differences in the field are not genetically fixed.
Step 2: Analyze option (A).
Phenotypic plasticity refers to the ability of the same genotype to produce different phenotypes under different environmental conditions.
The change from creeping (rocky sites) to upright growth (greenhouse) strongly supports phenotypic plasticity.
Hence, (A) is correct.
Step 3: Analyze option (B).
Inbreeding depression typically results in reduced fitness, such as lower growth or reproduction.
There is no evidence here linking creeping growth form to inbreeding effects.
Hence, (B) is incorrect.
Step 4: Analyze option (C).
If high gene flow restricted local adaptation, populations would not show consistent habitat-specific morphologies in nature.
However, clear morphological differences are observed in the field.
Hence, (C) is not supported.
Step 5: Analyze option (D).
The experiment does not provide information about the genetic architecture (polygenic vs single-gene control) of growth form.
Environmental responsiveness alone cannot be used to infer polygenic inheritance.
Hence, (D) is incorrect.
Step 6: Conclusion.
The greenhouse experiment demonstrates that growth form in Veronica depends on environmental conditions rather than fixed genetic differences.
Therefore, the correct explanation is: \[ \boxed{(A)} \]