Research with Kenyon Students

General topics

I have collaborated with students in two areas of research, linked conceptually by the process of dispersal of individuals within and between populations. These two areas are the ecology of seed dispersal by ants, and the population structure of fish in headwater streams.

Ants disperse seeds of many plants. In Ohio, many of these plants flower in the early spring in the understory of moist forests; up to two-thirds of these spring-flowering, understory perennials produce seeds with special, external fat bodies. Ants respond to these seeds by carrying them back to nests, where the fat bodies are consumed before the "cleaned" seeds are abandoned or dumped outside the ant nest. What behavioral cues stimulate carrying behavior? Why do ants often stop carrying this kind of food before the seed supply is depleted? How is gene exchange among plants influenced by short (1 to 3 meters) dispersal distances? Is plant recruitment limited by competition for the services of ants? Do ant colonies produce more workers or reproductives if they have access to such seeds? We use field monitoring, experimental methods, and spatial modeling to address these questions.

In headwater streams, fish populations are distributed in a "linear" ecosystem, which raises questions about free exchange of genes through a watershed. Does the amount of gene exchange allow fish to adapt to the local selection pressures imposed by different land use patterns? This is an important question because headwater streams are especially influenced by the materials flowing into them from surrounding land - the aquatic and terrestrial ecosystems are linked intimately. In Knox County, Ohio, agricultural practices are highly varied, but of sufficient quality to allow the Kokosing River to be designated an Ohio Scenic River. We are looking for genetic markers to allow us to detect potential problems in headwater streams, and we are using genetic markers to better understand the population structure of fish in linear, non-equilibrium systems such as the Kokosing River watershed. Depending on whether we wish to examine potential response to selection or to measure fine-scale genetic structure, we use allozyme markers or RAPDs analysis. In addition, we use laboratory studies to test for response to selection.

Some papers and abstracts with student co-authors

Comments or Suggestions to: Ray Heithaus at heithaus@kenyon.edu

Edited: 8/16/02

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