tested in this study were plant age (1- or 5-yr-old), leaf age (young or mature, which were
easily distinguished based on leaf color and texture) and fertilization treatment
(unfertilized or fertilized). Beetles were collected from 1-yr-old plants in the field and
then starved for approximately 24 hr in the laboratory. I then placed each of 48 randomly
selected individuals in a breathable plastic bag for 24 hr with one freshly collected C.
alliodora leaf. All leaves were collected from the same plot and all had relatively little
insect damage to control for herbivory-induced changes in palatability. I conducted three
trials with identical treatments and experimental procedures, with each trial containing
six replicates of the eight treatment combinations (N=144 beetles tested). To quantify
herbivory I measured the initial and final leaf area with a Licor 3100 area meter.
Because the young leaves lost area due to reduced turgor pressure over the course of the
experiment, I used a correction factor derived from a linear regression equation based on
the initial area to calculate their change in area due to shrinkage (y = 0.9934x 0.7378, R2
= 0.9988, P < 0.001). I used a block design ANOVA to test for main and interaction
effects of the treatments on the amount of leaf material consumed, with the trial as the
block factor to account for random temporal effects.
Results
Field Survey of Herbivory
One to 16 leaves were present within 10 cm of focal domatia (mean SD = 6.2
3.1), and the total leaf area before herbivory ranged from 4.6 to 310.8 cm2 (mean SD =
96.9 60.9 cm2). There were no significant effects of plant age or fertilization on the
number of leaves (Table 3-1), but the total leaf area was marginally significantly larger
for the 5-yr-old plants (Table 3-2). Although the leaf area varied within both ages, the 5-