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Research: Past Projects

Collaborative research: periodical cicadas and forest community dynamics
Keith Clay (professor, IU Dept. of Biology) with James Speer (assistant professor, Indiana State University)

This project analyzed the ecological effects of the 2004 emergence of the 17-year periodical cicadas (Brood X), likely the largest insect outbreak on Earth. Visit the Cicada Project Web site for more information.

In addition, IU RTP and Wonderlab created an interactive presentation about the cicadas for schoolchildren with a grant from the National Science Foundation. It also authored an award-winning, feature-length documentary.

Understanding physiological integration of environmental signals: how an experimental food resource pulse signals initiation of reproduction in the seasonally breeding deer mouse
Tim Greives (graduate student)

I am interested in how environmental signals are translated to physiological signals used by a seasonally breeding rodent, the deer mouse, to time breeding to coincide with favorable environmental conditions. More specifically I will investigate how food supplementation during the winter affects leptin, a hormone secreted by white adipose tissue, and how the brain interprets this signal, combined with changing day length, to initiate the hormonal cascade that initiates reproductive behaviors and organ growth (testes and ovaries).

Soil, water, and terrain influences on plant distributions in an old field
Adam Davis (graduate student), and Greg Olyphant (associate professor), IU Dept. of Geological Sciences

The effects of soils, hydrology and geomorphology on plant distributions are not well quantified for old fields that are undergoing secondary succession towards temperate forest. Geographical correlations among the soil properties, slope character, and plant types have not been extensively explored in abandoned fields.

Research at Griffy Lake:
A small, mid-successional field in the southwestern upland portion of the Griffy Lake Preserve affords a good opportunity to examine the geographical distribution of plant species and possible relationships of this distribution to soil and landform characteristics.

Why should anyone care?
Understanding how soils and landforms affect plant communities is important in estimating natural resources in the present and the future. This work will assist in predicting plant community development over time on disturbed sites based on the character of soils and terrain.

Changes in the density and composition of non-native invasive shrubs as the distance to a road increases
S. Luke Flory (graduate student, IU Dept. of Biology)

The purpose of this study is to determine the relationship of invasive shrub species to the proximity of a road. This research will examine the changes in the density and composition of non-native invasive shrubs as the distance from a road increases into mature forests vs. old fields. The goal is to determine if the presence of a road has a role in the invasion of exotic shrub species. Species to be examined include multiflora rose, bush honeysuckle, autumn and russian olive, and common privet. The results of this project will aid in the management of invasive shrubs.

Effects of periodical cicadas on the nitrogen nutrition and competitive balance of forest understory species.
Nicholas Worley (honors thesis undergraduate student, IU Dept. of Biology)

The emergence and death of periodical cicadas creates a large pulse of nitrogen for plant communities, and this project examines the effects of cicada-derived nitrogen inputs on the competitive balance of common native and invasive forest herbs and grasses. Three native woodland species ("Bottlebrush Grass" - Elymus hystrix, "Tall Bellflower" - Campanula americana, and "White Snakeroot" - Eupatorium rugosum) were grown in greenhouse communities with and without the invasive woodland species ("Garlic Mustard" - Alliaria petiolata). Four types of cicada treatments were applied to all communities: no cicadas, dead adult cicadas, cicada exoskeletons, and dead cicadas and exoskeletons. Effects of the cicadas on plant nitrogen nutrition and competitive performance are being assessed via analysis of plant biomass and nitrogen concentration.

Invasive and non-invasive plant community composition at Griffy Woods
Gabriel Harp (graduate student, IU Dept. of Biology)

The goal of this project is to define sampling procedures and plots to monitor plant community composition and the spread of invasive species in the Griffy Preserve. These methods may then be used to develop long-term datasets that can inform future scientific endeavors and resource management decisions. Additional effort will be directed toward identifying campus groups that may be interested in performing future sampling at these sites.

Transmission mode and virulence in a plant/fungal interaction
Tammy Johnston (graduate student, IU Dept. of Biology)

This research will examine the relationship of parasite transmission mode and virulence. The host, Elymus hystrix, is a woodland grass that is commonly parasitised by the endophytic fungus, Epichloë elymi. This parasite is transmitted vertically, through the host's seeds, and horizontally, via sexual spores produced by a host castrating fungal stroma. Both the host grass and its fungal parasite occur at the IU RTP.

Queen-worker conflict over colony sex ratio in the acorn ant, Leptothorax curvispinosus
Tim Linksvayer (graduate student, IU Dept. of Biology)

Parent-offspring conflict theory suggests that a colony's queen and workers will disagree over the optimal colony sex ratio of male and female reproductives. Queens are equally related to their sons and daughters, but female workers are more closely related to their sisters than to their brothers, so that queens favor a 1:1 sex ratio but workers favor a female-biased sex ratio. Although the queen has control of the initial sex ratio of eggs, workers rear the brood and may be able to change the initial sex ratio by killing males or underfeeding females so that they develop into workers instead of queens. I have collected 200 potential acorn nests of the acorn ant, Leptothorax curvispinosus, every month for seven months, and am currently censusing all of the ant occupants and genotyping a portion of the ant queens, workers, and brood. With these data, I will be able to examine how queen-worker conflict over the colony sex ratio is resolved over the course of a season, as well as how colony and population structure change over the course of a season.

Soil-borne pathogens and tree recruitment in temperate forests
Alissa Packer (postdoc) and Keith Clay (professor), IU Dept. of Biology

Plant-soil interactions affect plant population dynamics and community interactions. Both positive and negative feedbacks may occur where soil microbiota either favor the survival and growth of a particular species or actively inhibit it. Negative feedback has recently been documented between black cherry (Prunus serotina), and soil-borne fungal pathogens in the genus Pythium that inhibit seedling establishment in the vicinity of adult trees, in accordance with the Janzen-Connell hypothesis (Packer and Clay, 2000). The objectives of our ongoing research are to determine how negative feedback changes with successional age of the community, to assess the host specificity of Pythium species causing damping-off in black cherry, and to evaluate whether other temperate tree species are affected in a similar way by soil-borne pathogens. A series of field, greenhouse and laboratory experiments are being used to explore the role of soil-borne pathogens as regulators of seedling establishment, spatial dynamics and successional change within temperate forest communities. Our results will provide valuable comparative data with results from tropical forests, and will have practical applications for forest and orchard management, and ecological restoration.

Packer, A. and K. Clay. 2000. Soil pathogens and spatial patterns of seedling mortality in a temperate tree. Nature 404: 278-281.

Nitrogen deposition: the ecological response of vegetation and soil in early- versus late-successional forests of southwestern Indiana
Chris Swan (undergraduate student, IU Environmental Science Program)

Forests provide key ecosystem services such as preservation of biodiversity and purification of air and water, yet are under increasing threats from human activities. Anthropogenic influences on forests include clear-cutting for timber, nitrogen pollution from fossil fuel combustion and introductions of exotic species. The focus of my research is to compare the susceptibility of early- (recently logged) and late-successional temperate deciduous forests to nitrogen loading. Vegetation dynamics (resistance to invasive exotic species, changes in species richness, root to shoot biomass, chemical composition) and soil characteristics (nitrogen retention, aluminum solubility, pH) are being examined under normal vs. nitrogen-loaded conditions in greenhouse and field experiments (Figures 1, 2). This research will yield better understanding of the capacity for temperate deciduous forest to absorb atmospheric nitrogen deposition as the result of anthropogenic production.

Salamander population baseline survey of Griffy Woods preserve
Jonathan Mull (undergraduate student, IU Public Affairs Program)

The purpose for this research is to conduct a baseline study of salamander populations on Griffy Woods preserve. Acquiring a baseline survey of population will provide information on species composition, population size, and reproduction activities. At this point, no research on salamander populations has occurred on the Griffy Woods Preserve site. From the baseline data, information can be used to begin other research on salamanders. This information can be used by others in the field to monitor trends in population in the future. Artifical cover objects are being used to simulate the natural habitat of salamanders and provide a systematic research methodology. Cover objects (30 x 45 cm) will be constructed with carpet runner covering carpet padding on the underside. Carpet runner keeps the padding from becoming too wet or too dry. Carpet padding is used because of its moisture retention that will create moist cover resembling suitable habitat for salamanders. Cover objects will be placed on five 200-meter transects running parallel (east to west) to the eastern most ridge in the Griffy preserve. Transects located at bottom, middle, and top of the north and south facing slopes sample the micro-habitat and climate types created by the varying levels of solar exposure.

Revised: December 15, 2008

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