Answers to Figure Legend Questions

FIGURE 12.2 The peak abundance of lynx usually occurs after the peak abundance of hares. One reason this might occur is that as hare abundance rises, the increased availability of food enables the lynx to produce more offspring; however, these offspring are not born immediately, so the rise in lynx abundance lags behind the rise in hare abundance.

FIGURE 12.7 To answer this question, we must use the data in the graph to determine the total number of agromyzid fly species and the number of agromyzid fly species that feed on fewer than five host plant species. We can do this using the scale on the y axis, which indicates that a bar that is 2.15 cm in height represents 50 fly species. Measuring all 13 bars on the graph, we find that their heights sum to 12.05 cm; this indicates that in total, there are about 280 fly species (280 = 12.05 cm/2.15 cm ? 50). Similarly, the heights of the four bars representing fly species that feed on fewer than five host plant species sum to 10.4 cm, indicating that about 242 fly species feed on fewer than five host plant species. Thus, about 86% of agromyzid fly species feed on fewer than five host plant species.

FIGURE 12.11 On average (based on the height of the bar graph), the control plants produced about 11 or 12 fruits per plant. This indicates that a plant that compensated fully for clipping would also produce 11 or 12 fruits.

FIGURE 12.17 The density of other plants in the community would probably increase after herbivory by C. quadrigemina reduced the density of Klamath weed. Because Klamath weed was originally a dominant member of the community, it is likely that the community would change considerably after introduction of the beetle.

FIGURE 12.21 In the absence of snails, wetlands had phosphorus concentrations of less than 100 μg∕L. When snails were present, phosphorus concentrations were usually much greater than 100 μg∕L; for example, in the seven wetlands with snail densities greater than 10 snails per square meter, the average phosphorus concentration was close to 1,000 μg∕L. Thus, the presence of snails is associated with an increase in the phosphorus concentration of these wetlands.