Question

Two bird species, \(A\) and \(B\), are found on a single mountainside. \(A\) is a low-elevation species, found between 500 m and 1500 m Above Sea Level (ASL), while \(B\) is a high-elevation species, found between 1000 m and 2000 m ASL. At 1250 m ASL, species \(A\) and \(B\) have very different bill morphologies, but the bill morphology of species \(A\) at 500 m is very similar to the bill morphology of species \(B\) at 2000 m ASL. Which one or more of the following explain(s) the difference in bill morphology at 1250 m ASL?

• A. Competitive exclusion
• B. Character displacement
• C. Convergent evolution
• D. Allopatric speciation

Hint:

To understand trait divergence:
1. Sympatric populations often show divergence to reduce competition.
2. Compare traits in overlapping and non-overlapping ranges to identify ecological processes.

Answer 1

The Correct Option is B

Step 1: Analyze the ecological context. At 1250 m ASL, \(A\) and \(B\) coexist and show distinct bill morphologies, likely to reduce competition. However, their morphologies are similar at non-overlapping elevations, indicating the differences at 1250 m are ecologically driven. Step 2: Evaluate the processes. Competitive exclusion: Unlikely, as both species coexist. Character displacement: Likely, as sympatric divergence reduces competition. Convergent evolution: Explains similarity at non-overlapping elevations but not divergence at 1250 m. Allopatric speciation: Does not explain divergence in sympatry.