Many species in mountain ranges are shifting their ranges to higher, cooler elevations in response to warming temperatures because of climate change. The graph above shows how the midpoint of elevational range in the year 2025 is related to the midpoint of the elevational range in the year 2000 for species in temperate (open circle) and tropical (solid circle) mountain ranges. Each point represents a species, and the dashed line is the 1:1 or the identity line (with intercept = 0 and slope = 1). Which one of the following statements is consistent with the above graph?
Show Hint
Distance above the 1:1 identity line shows how much a species range has shifted upward; compare that distance for solid (tropical) versus open (temperate) points.
Tropical species are more sensitive than temperate species to temperature change
Temperate species are more sensitive than tropical species to temperature change
Both tropical and temperate species are equally sensitive to temperature change
No conclusion can be reached about the relative sensitivities of tropical and temperate species to temperature change
Show Solution
The Correct Option isA
Solution and Explanation
Step 1: Turn the picture into a simple number.
For any species, compute the residual $r = (\text{2025 midpoint}) - (\text{2000 midpoint})$. On the identity line, $r=0$. Points above the line have $r>0$, meaning the species moved to a higher elevation, and a bigger $r$ means a bigger shift.
Step 2: Estimate the typical residual for each group.
Reading across the plot, the tropical (solid) points sit noticeably higher above the dashed line than the temperate (open) points do, at almost every position along the x-axis. So the average $r$ for tropical species is clearly bigger than the average $r$ for temperate species.
Step 3: Connect residual size to sensitivity.
A bigger residual means a bigger upward range shift for the same amount of warming, which is exactly what "more sensitive to temperature change" means in this context. Since tropical species show the bigger residual, they are the more sensitive group.
Step 4: Check the remaining choices.
The claim that temperate species shift more does not match the picture, since their points sit closer to the line. The claim of equal sensitivity would need both sets of points to sit at a similar distance from the line, which they do not. The claim that no conclusion is possible does not hold either, since the two groups are visibly separated in how far they sit from the identity line.
Step 5: Conclude.
\[ \boxed{\text{Tropical species are more sensitive than temperate species to temperature change}} \]
