Effect of previous herbivory on subsequent herbivore performance

QUINTERO C, MD BOWERS

Fort Collins, Colorado

Simposio; 14th Front Range Student Ecology Symposium; 2008

Colorado State University Ft. Collins

Plant secondary compounds play an important role on specialist herbivore performance as well as mediating inter- and intra-specific competition among herbivores. Increased level of plant defense after damage can change plant quality and palatability of a host, indirectly affecting subsequent conspecific or heterospecific herbivores. Because induced defenses can be species-specific, the identity and history of herbivores inflicting damage on the same host may be essential to understand plant and herbivore population dynamics. A greenhouse experiment was performed rearing a specialist sequestering caterpillar Junonia coenia (Nymphalidae) on three Plantago lanceolata diet-treatments: 14-week-old plantains undamaged or damage by specialist (J. coenia) or generalist (Spilosoma virginica) herbivore at the age of 9 weeks. Twenty plants per diet-treatment were harvested to measure levels of plant toxins among treatments. Other 20 plants per treatment were subject to damage by two J. coenia larvae from 3rd to 5th instar. Besides the dissimilar history of damage, the three diet-treatments were not different in secondary compounds levels. However, history of damage does have an effect on J. coenia’s performance. Caterpillars reared on undamaged plants gained more biomass than caterpillars reared on previously damaged plants; but no difference was observed between specialist or generalist damaged plants. In contrast, quantification of secondary compounds on larval tissues demonstrated that caterpillar reared on undamaged plants sequestered significantly less toxins than those reared on previously damaged plants. Moreover, caterpillars sequestered significantly more toxins if feeding on plants previously damaged by specialist than generalist caterpillars. These results suggest a trade-off between growth rate and defensive status which might be caused by: a) increased levels of plant chemical defense during larval development, escalating the cost of resources uptake, or b) by being previously damaged plants a lower quality resource in terms of nutrient concentration.