Photos: Cuscuta salina parasitizing Salicornia virginica in a California salt marsh.
I am interested in how interactions between parasitic plants and host plants parallel or contrast with interactions between herbivores and plants. Parasitic plants are common in natural communities but are often overlooked in ecological theory. Interactions between parasitic plants and hosts often parallel those between herbivores and plants. In other cases, basic differences in mobility, hormonal and elemental composition and resource capture between plants and animals lead to different effects. Many fundamental aspects of the ecology of parasitic plants remain poorly studied.
Parasitic plants can have strong impacts on natural communities. In collaboration with Dr. Ragan Callaway, I have studied the impacts of Cuscuta salina on plant communities in southern California salt marshes. We found that Cuscuta preferentially attacked Salicornia virginica over most other plants in the marsh. Because Cuscuta could strongly depress biomass of Salicornia, it mediated interactions between Salicornia and other plant species, altering zonation patterns and increasing plant diversity. My student Emily Marquardt also studied aspects of Cuscuta host choice in Texas salt marshes.
Some recent parasitic plant publications:
Marquardt, E. S. and S. C. Pennings. 2011. Diet mixing in a parasitic plant: adaptation or constraint? Plant Ecology 212:69-77.
Marquardt, E. S. and S. C. Pennings. 2010. Constraints on host use by a parasitic plant. Oecologia 164:177-184.
Pennings, S. C., Simpson, J. C. 2008. Like herbivores, parasitic plants are limited by host nitrogen content. Plant Ecology 196:245-250.
Pennings, S. C. and R. M. Callaway. 2002. Parasitic plants: parallels and contrasts with herbivores. Oecologia 131:479-489.
Callaway, R. M. and S. C. Pennings. 1998. Impact of a parasitic plant on the zonation of two salt marsh perennials. Oecologia 114:100-105.
Pennings, S. C. and R. M. Callaway. 1996. Impact of a parasitic plant on the structure and dynamics of salt marsh vegetation. Ecology 77:1410-1419.