Figure 3. Treatment means from the bi-trophic experiment.

Effects of intra- vs. inter-specific competition and genetically based variation in host plant Baccharis salicifolia quality on the fecundity of a generalist (Aphis gossypii) and a specialist (Uroleucon macolai) herbivore. The effects of genetically based variation in host plant quality are tested by comparing herbivore fecundity between male and female plants (panels A, B) and among 14 plant genotypes (panels C, D). For effects of plant sex, means (± 1SE) are shown for each competition treatment. For effects of plant genotype, overall means (± 1SE) are shown for each competition treatment, and means for individual genotypes (error bars omitted for clarity) are indicated with solid (male) or dashed (female) lines. See Table 2 for statistics.