Plant-herbivore interactions

Photo: Caterpillar eating Spartina alterniflora in Maine.

Photo: Paroxya grasshopper eating Iva frutescens in Georgia.

Photo: Orchelimum grasshopper eating Spartina alterniflora in Georgia.

Photo: Omnivorous Armases crab, common in southeastern U.S. salt marshes.

Photo: Trirhabda beetle feeding on Baccharis in Texas.

I am interested in the factors that mediate herbivore feeding choices.  Despite decades of interest, we do not have a general, predictive understanding of why herbivores eat the particular plants that they do.  A variety of plant traits, including toughness, nitrogen content, minerals (silica in higher plants, calcium carbonate in seaweeds), and chemical defenses may all affect the palatability of plants, but it is difficult to predict which plant traits will matter to particular herbivores in particular cases.  I have studied this issue using a variety of organisms, including gastropods, isopods, sea urchins, fish and insects.  I am also interested in the possibility that feeding specialization may be selected against in some organisms because a mixed diet is more nutritious than any single food.

I am also interested in how plant-herbivore interactions change across gradients.  Much of my current research focuses on latitudinal gradients in plant-herbivore interactions in salt marshes along the Atlantic coast of the U.S.  A major dogma of biogeography is that consumer-prey interactions are more intense at lower latitudes.  If this is true, prey should have evolved increased defenses (i.e., be less palatable) at low versus high latitudes.  My students and I are examining these hypotheses using a suite of plant species that occur in coastal salt marshes from Florida into New England.  Results to date indicate that 1) there is a community-wide pattern for southern plants to be less palatable than northern plants, 2) that a variety of plant traits may contribute to this pattern, 3) that this pattern has a strong genetic component, 4) that herbivore pressure may be one selective factor contributing to this pattern, and 5) that similar patterns occur in European salt marshes.

Our current work in this area focuses on putting the plant-herbivore interaction into a broader trophic context.  In collaboration with Dr. Robert Denno, we are examining latitudinal variation in top-down and bottom-up interactions in Atlantic coast salt marshes.  We are testing a variety of hypotheses about how latitudinal variation in plant quality, predator abundance and omnivore abundance mediates herbivore abundance and herbivore damage to plants.

I am also interested in how interactions between parasitic plants and host plants parallel or contrast with interactions between herbivores and host plants (see parasitic plant link).

Some recent plant-herbivore publications: