Two co-occurring plant species, A and B, flower at the same time. They are visited by the same pollinator species. If these plants are pollinator-limited, then which one or more of the following statements is/are correct with regard to the figure shown below?
Show Hint
Shannon index steps: (1) restrict to the focal group, (2) convert to proportions that sum to 1, (3) compute \(p_i\ln p_i\) with natural log, (4) sum and negate, (5) compare with \(\ln S\) to gauge evenness (\(E=H/\ln S\); here \(E\approx 1.19/1.386\approx 0.86\)).
Step 1: Interpret the graph.
The y-axis shows pollination of species A, and the x-axis shows the density of flowers of species B. Three lines (1, 2, 3) depict possible relationships:
- Line 1: Negative slope (as B increases, A’s pollination decreases).
- Line 2: Flat (B’s density has no effect on A).
- Line 3: Positive slope (as B increases, A’s pollination increases).
Step 2: Match ecological interactions.
- \emph{Competition:} When both species share the same pollinator and more flowers of B reduce visits to A, this is competition. That matches Line 1.
- \emph{Neutral interaction:} No effect means independence, not mutualism. That matches Line 2, but the option “mutualism” is wrong here.
- \emph{Parasitism:} Would mean one benefits while the other is harmed. Here, Line 3 shows A benefits when B is more abundant — this is not parasitism, but \emph{facilitation}.
- \emph{Facilitation:} If B attracts more pollinators overall, A also benefits. That is Line 3.
Step 3: Evaluate statements.
(A) Line 1 = competition — Correct.
(B) Line 2 = mutualism — Incorrect, it shows neutrality.
(C) Line 3 = parasitism — Incorrect, it shows facilitation.
(D) Line 1 = facilitation — Incorrect, it shows competition. Final Answer:
\[
\boxed{\text{(A)}}
\]
