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: Focus on the main experimental result. 
Plants collected from rocky habitats and grasslands were raised under the same greenhouse environment.
Although these plants show very different growth forms in natural conditions, all of them produced upright stems in the greenhouse.
This clearly suggests that the differences seen in the field are not permanently encoded in their genes.

Step 2: Evaluate option (A).
Phenotypic plasticity is the capacity of a single genotype to express different physical forms when exposed to different environments.
The shift from creeping growth in rocky areas to upright growth under greenhouse conditions fits this definition perfectly.
Therefore, option (A) is correct.

Step 3: Evaluate option (B).
Inbreeding depression usually manifests as reduced vigor, survival, or reproductive success.
There is no indication that the creeping growth habit is associated with reduced fitness or inbreeding effects.
Hence, option (B) is incorrect.

Step 4: Evaluate option (C).
If strong gene flow were preventing local adaptation, distinct growth forms would not consistently appear in different habitats.
Since clear habitat-specific morphologies are observed in nature, this explanation is not supported by the data.
Thus, option (C) is incorrect.

Step 5: Evaluate option (D).
The experiment does not reveal whether growth form is controlled by one gene or many genes.
Environmental responsiveness alone cannot be used to conclude that a trait is polygenic.
Therefore, option (D) is incorrect.

Step 6: Final conclusion.
The greenhouse results show that growth form in Veronica is shaped by environmental conditions rather than fixed genetic differences.
The most appropriate explanation is:

\[ \boxed{(A)} \]