CHRISTOPHER J. PARADISE

Associate Professor of Biology

Specialty Areas: Community Ecology, Aquatic Entomology, Invertebrate Zoology, & Environmental Science

Telephone: (704)894-2890

Office: 272 Watson Life Sciences

Email: chparadise@davidson.edu

Education

· B.S., SUNY Albany, 1986

· M.A., Binghamton University, 1989, Advisor: Dr. Nancy E. Stamp

· Ph.D., The Pennsylvania State University, 1997, Advisor: Dr. William A. Dunson

Research Interests and Philosophy

The role of abiotic factors in the organization of communities is one of the most fundamental questions in ecology. Heterogeneity of abiotic factors has been hypothesized to alter the outcome of biotic interactions and influence top-down and bottom-up factors. Additionally, the relative importance of top-down vs. bottom-up factors is a prominent debate in contemporary ecology. I am interested in how biotic interactions are mediated by abiotic factors, and how changing interactions may affect community structure. I am especially interested in the role resource availability plays in dynamic interspecific interactions. I use a variety of approaches to investigate these concepts, from whole community field monitoring to manipulative field and laboratory experiments on single species and subsets of communities.

One bottom-up factor that may be critical to forest aquatic systems is energy input in the form of leaf litter. Treehole habitats, the system I have been studying, are easily manipulated forest aquatic systems that occur as small, discrete habitats and thus make excellent model communities to study effects of resources and abiotic factors. Leaf litter forms the basis of a processing chain wherein resources change condition over time and consumers specialize on resources in different condition. Consumers may therefore play a role in determining resource abundance, thus having an important community-wide influence. One outcome of processing chains is a commensalism, where "upstream" consumers break down the resource, thereby providing resources in another form to "downstream" consumers. The interaction involves organisms in the middle of the food web that are affected by bottom-up forces, but in a way that is modulated by lower-level consumers.

I have discovered that leaf-shredding beetles in treeholes are consumers that mediate resource abundance to two other species of detritivores when resources are scarce. These beetles may act as keystone decomposers by increasing the rate of leaf litter decay, making resources more available to deposit and filter feeders. Facilitative interactions, such as this commensalism, have been shown in other ecosystems, and may be especially common in detritus-based communities. These interactions likely affect population dynamics and community structure, and constitute an important factor that is outside of the conventional community models of top-down / bottom-up control. I am interested in examining the strength of the interaction under different resource levels and water chemistry parameters. I have shown that certain abiotic factors such as pH and sodium concentration affect treehole species differentially and may interact with the processing chain commensalism. Both detritivores are more susceptible to acidification than the leaf-shredding beetles, and thus the beetles beneficial effect may disappear at low pH. Water chemistry, in turn, is dependent on atmospheric deposition patterns, indicating the importance of inputs into the system. The community is thus influenced by environmental heterogeneity and may change as the environment changes, highlighting the dynamic nature of communities.

The study of these and other detritus-based communities is relevant to questions of general ecological importance, as well as to questions regarding responses to changing environments. In the future I plan to continue investigating the effects of resources and abiotic factors on biotic interactions and community structure, using a variety of detritus-based communities. I am specifically interested in examining the prevalence of processing chain commensalisms in these communities, and the relationships of processing chain commensalisms to resource levels and abiotic factors, as well as the possibility that upstream consumers can affect the whole community as keystone species.