Mody Karsten, Unsicker Sybille B, Linsenmair K Eduard
Department of Animal Ecology and Tropical Biology, Biozentrum, Am Hubland, D-97074 Würzburg, Germany.
Ecology. 2007 Apr;88(4):1012-20. doi: 10.1890/06-1338.
Generalist insect herbivores may profit by feeding on a mixture of plant species that differ in nutritional quality. Herbivore performance can also be affected by intraspecific host plant variation. However, it is unknown whether conspecific plant individuals differ sufficiently to promote diet-mixing behavior in specialist herbivores. We experimentally tested this "specialist diet-mixing hypothesis" for specialist caterpillars (Chrysopsyche imparilis, Lasiocampidae) in a West African savanna. The caterpillars switched regularly between host tree individuals (Combretum fragrans, Combretaceae). To examine whether switching benefited caterpillar performance via diet-mixing, the caterpillars were reared either on leaves from several plant individuals (mixed diet) or on leaves from a single plant. The strongest effect of diet-mixing was found for fecundity, with females reared on a mixed diet laying significantly more eggs than sisters receiving a single-plant diet. In addition, a mixed diet decreased variability in egg size and increased the growth of second-instar caterpillars. Supplementary food choice experiments were conducted to assess a potential influence of lowered host quality (induced by herbivory) on caterpillar behavior; no such effect was found. By linking intraspecific host-switching behavior and herbivore performance, this study provides new information on the relevance of intraspecific plant variation for herbivorous insects.
多食性昆虫食草动物可能会因取食营养质量不同的多种植物而受益。食草动物的表现也可能受到种内寄主植物变异的影响。然而，同种植物个体之间的差异是否足以促使专食性食草动物产生混合取食行为尚不清楚。我们在西非稀树草原对专食性毛虫（Chrysopsyche imparilis，枯叶蛾科）进行了实验，以验证这一“专食性混合取食假说”。毛虫会在寄主树个体（Combretum fragrans，使君子科）之间定期转换。为了检验转换取食是否通过混合取食使毛虫受益，我们将毛虫分别饲养在来自多个植物个体的叶片上（混合饮食）或来自单一植物的叶片上。混合取食对繁殖力的影响最为显著，以混合饮食饲养的雌虫产卵量明显多于取食单一植物饮食的姐妹。此外，混合饮食降低了卵大小的变异性，并促进了二龄毛虫的生长。我们还进行了补充食物选择实验，以评估寄主质量下降（由食草作用引起）对毛虫行为的潜在影响；但未发现此类影响。通过将种内寄主转换行为与食草动物表现联系起来，本研究提供了关于种内植物变异对食草昆虫相关性的新信息。
