Forest patches are embedded within a landscape dominated by crop fields. The crop fields around fragmented forest patches are thought to affect the abundance of different butterfly species to different extents. The graph above shows the pattern of butterfly abundance (means, and error bars representing 95% confidence intervals) of three species, M, N, and O between the forest patches and the crop fields. Which one of the following options best describes the impact of fragmentation on the three different butterfly species?
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Compare each species' mean and confidence interval in the forest against the crop fields; non-overlapping intervals with a big gap mean a strong effect, overlapping intervals mean a weak one.
M - strongly positive; N - weakly negative; O - strongly negative
M - strongly negative; N - weakly positive; O - strongly positive
M - strongly negative; N - weakly positive; O - strongly negative
M - strongly negative; N - weakly negative; O - strongly positive
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The Correct Option isD
Solution and Explanation
Step 1: Read the pattern for species M.
In the forest, species M has a high mean abundance, close to 18. In the crop fields, its mean drops to about 3, and the two confidence intervals (forest around 16 to 20, and crop fields around 1 to 5) do not overlap at all. This is a large drop with no overlap, so M shows a strongly negative response to the crop field habitat.
Step 2: Read the pattern for species N.
Species N starts at about 15 in the forest and falls only to about 13 in the crop fields. The two confidence intervals are close together and mostly overlap. The change is small and not clearly separated, so N shows only a weakly negative response, a slight decline rather than a sharp one.
Step 3: Read the pattern for species O.
Species O starts very low, close to 2, in the forest and rises to about 11 in the crop fields. The confidence intervals in the forest (roughly 1 to 3) and in the crop fields (roughly 9 to 13) are clearly separated. This is a large rise with no overlap, so O shows a strongly positive response to the crop field habitat.
Step 4: Match this pattern to the options.
We need M strongly negative, N weakly negative, and O strongly positive. Option (A) gives M as strongly positive, which is wrong. Option (B) gives N as weakly positive, which is wrong since N actually falls slightly. Option (C) gives O as strongly negative, which is wrong since O actually rises sharply. Only option (D) lists M strongly negative, N weakly negative, and O strongly positive, matching the graph exactly.
Step 5: Final Answer.
\[
\boxed{\text{M - strongly negative; N - weakly negative; O - strongly positive}}
\]
