To duck or not to duck: resistance advantages and disadvantages of the candy-cane stem phenotype in tall goldenrod, Solidago altissima
Author for correspondence:
Michael J. Wise
Tel:+1 540 837 2067
- •Solidago altissima populations consistently contain a minority of ‘ducking’, or ‘candy-cane’, stems. The goals of this study were to investigate whether these candy-cane stems may be an adaptation to resist herbivory, and to look for costs (namely, resistance tradeoffs or reduced reproduction) that might constrain the spread of the ducking trait.
- •In this study, herbivory and seed set were recorded for 272 erect and 272 candy-cane stems in a field population of S. altissima.
- •Candy-cane plants were twice as resistant as erect plants to two common apex-attacking gall midges, but were 26% more susceptible than erect plants to a more abundant apex-boring caterpillar. The two stem morphs were equally resistant to all other herbivores surveyed. Candy-cane plants were 11% less likely to experience apex damage and 3% more likely to set seed than erect-stemmed plants. Damaged candy-cane stems were 9% more likely to produce seeds than damaged erect stems.
- •Although ducking is an effective means of resisting apex-galling herbivores, its spread may be constrained by susceptibility to an apex-boring caterpillar, which may enjoy enemy-reduced space on candy-cane stems. The evolution of ducking does not seem to be constrained by a reduced likelihood of sexual reproduction, or reduced tolerance of apex damage.