Question

Islands I, II, and III lie off a mainland coast. Which one of the following statements about species richness is consistent with the theory of island biogeography?

• A. Island II has the highest species richness because it has the lowest area.
• B. Island III has the highest species richness because it is large and farthest from the mainland.
• C. Island I has the highest species richness because it is large and closest to the mainland.
• D. Islands I and III have equally high species richness because they have roughly the same area.

Hint:

For \(N=aH^2+bH+c\): the sign of \(a\) sets the shape (\(a>0\)\,: U-shaped; \(a<0\)\,: inverted). The vertex (optimum) is at \(H^\*=-\dfrac{b}{2a}\); completing the square also gives the minimum/maximum value immediately.

Answer 1

The Correct Option is C

Step 1: Two key predictions of island biogeography. \begin{enumerate}
Area effect: larger islands have lower extinction rates \(\Rightarrow\) higher equilibrium richness.
Distance effect: islands closer to the mainland have higher immigration rates \(\Rightarrow\) higher richness. \end{enumerate}

Step 2: Apply to the map.
From the figure: - Island I is large and near the mainland \(\Rightarrow\) high immigration, low extinction. - Island II is small (and intermediate distance) \(\Rightarrow\) low richness. - Island III is large but far, so immigration is reduced; richness lower than a similar-sized near island.

Step 3: Evaluate options.

(A) Incorrect — smallest area gives lowest richness.
(B) Incorrect — distance reduces immigration despite large area.
(C) Correct — combines both favorable factors (large + near).
(D) Incorrect — equal areas don’t imply equal richness when distances differ. Final Answer:
\[ \boxed{\text{(C) Large and close island (I) has the highest species richness}} \]