Ecology and evolution go hand-in-hand, and perhaps nowhere is the link between these two fields clearer than in the study of plant defenses: the conspicuous prickles, toxic chemicals, and defensive mutualisms that have long fascinated plant ecologists are all the result of evolutionary arms races between plants and herbivores that have played out over millennia. The combination of comparative phylogenetic and classic field ecology methods is a powerful approach to understanding ecological and evolutionary patterns, whether across generations or genera.
Induced defenses (those produced after herbivore attack) are commonly considered a cost-saving strategy: plants produce defenses when they need them, and don't invest in them when they don't. Less well understood is why all plants don't rely on induced defenses, and how induced defenses might be lost over micro- or macroevolutionary timescales. Our work in this area indicates that induced defenses can be rapidly lost in the absence of herbivores, a pattern consistent with the idea that maintaining induced defenses may be costly. In Kenya, for example, we showed that the exclusion of megaherbivores for even a few years can lead to the loss in induced resistance in several species of Barleria. We showed this same pattern in half-sibling families of horsenettle (Solanum carolinense) in upstate New York that differed only in their previous exposure to insect herbivores: offspring of plants that had not been sprayed with insecticide responded to jasmonic acid by increasing investment in defense, whereas the offspring of plants that had historically been sprayed with insecticide (and thus did not experience herbivory) did not respond to the same treatment. Ongoing work in this area is aimed at understanding why induced defenses are lost more rapidly than their constitutive counterparts in some instances, and how various evolutionary drivers affect the balance of induced and constitutive resistance in plants.
Relevant publications:
Relevant publications:
- Coverdale, TC, IJ McGeary, RD O’Connell, TM Palmer, JR Goheen, M Sankaran, DJ Augustine, AT Ford, RM Pringle, and CE Tarnita. 2019. Strong but opposing effects of associational resistance and susceptibility on defense phenotype in an African savanna plant. Oikos 128:1772-1782.
- Coverdale, TC, JR Goheen, TM Palmer, and RM Pringle. Good neighbors make good defenses: associational refuges reduce defense investment in African savanna plants. 2018. Ecology 99: 1724-1736.
- Coverdale, TC and AA Agrawal. Experimental insect suppression causes loss of induced resistance to a specialist herbivore in horsenettle (Solanum carolinense) (Submitted)