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ROLES OF FOOD QUALITY AND ENEMY‐FREE SPACE IN HOST USE BY A GENERALIST INSECT HERBIVORE
Author(s) -
Singer Michael S.,
Rodrigues Daniela,
Stireman John O.,
Carrière Yves
Publication year - 2004
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/03-0827
Subject(s) - generalist and specialist species , herbivore , host (biology) , ecology , insect , biology , food chain , quality (philosophy) , habitat , philosophy , epistemology
The relative importance of food quality vs. enemy‐free space remains an unresolved but central issue in the evolutionary ecology of host use by phytophagous insects. In this study, we investigate their relative importance in determining host‐plant use by a generalist caterpillar, Estigmene acrea (Lepidoptera: Arctiidae). In nature, E. acrea late‐instar caterpillars preferred Senecio longilobus (Asteraceae), which contains pyrrolizidine alkaloids that the caterpillars sequester, over Viguiera dentata (Asteraceae), a natal host, and typically suffered a 28% mortality risk from parasitoids. We hypothesized that the natural, mixed diet of caterpillars provides high‐quality food via hosts like Viguiera as well as antiparasitoid defense via sequestered toxins from Senecio . We found that a pure Viguiera diet provides superior growth performance over a pure Senecio or mixed diet in the absence of parasitism. However, when parasitism risk is at least moderate, the mixed diet provides a survival advantage over the pure diets of Viguiera or Senecio . We therefore conclude that the balance between benefits of growth (food quality) and defense (enemy‐free space) maintains the use of a mixed diet in nature. Furthermore, the value of enemy‐free space supercedes the value of food quality in determining the host‐plant preference of late‐instar caterpillars.