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?
Show Hint
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
Show Solution
The Correct Option isD
Solution and Explanation
Step 1: Set the rule for judging strength and direction.
When the confidence intervals of two points do not touch, the change between them is a real, strong effect. When the intervals overlap a lot, the change is weak or not clearly present. Direction, positive or negative, just tells us whether abundance rises or falls from forest to crop field.
Step 2: Apply the rule to species M.
M sits near $18$ in the forest and near $3$ in the crop field, a drop of about $15$ units, and the error bars are far apart with no overlap. That is a strong, negative change.
Step 3: Apply the rule to species N.
N sits near $15$ in the forest and near $13$ in the crop field, a drop of only about $2$ units, and the error bars mostly overlap. That is a real but small drop, so this is a weak, negative change.
Step 4: Apply the rule to species O.
O sits near $2$ in the forest and near $11$ in the crop field, a rise of about $9$ units, with the error bars clearly apart. That is a strong, positive change.
Step 5: Combine and choose.
Putting the three together, M is strongly negative, N is weakly negative, O is strongly positive. This combination appears only in option (D); every other option gets at least one species wrong.
\[ \boxed{\text{M - strongly negative; N - weakly negative; O - strongly positive}} \]
