| Popis: |
Two very different factors favor generalist herbivores over specialist herbivores: greater resource availability, which should be universally beneficial, and the possibility of mixing foods to improve nutrient balance or to reduce exposure to high levels of particular allelochemicals. In this work, four species of Lepidoptera and three species of Hemiptera were fed single or mixed foods to test the hypothesis that individual generalists would benefit from mixing their diets. In all cases, insects were provided with one of three different host plants, or a mixture of all three. For most species, several different experiments were performed. Survivorship, gain in mass, and fecundity were used as measures of performance. In no case was there evidence that mixtures were better than single foods. It is argued that, in these taxa, the value of being a generalist lies largely with versatility for use of different hosts, rather than for dietary mixing. The contrast with Orthoptera, in which individuals commonly obtain substantial benefit from dietary mixing, is also discussed. |
Plný text