The 1999 Summer Research Fellows at Davidson are listed below, along with the name and abstract of their research project and the name of their faculty mentors:
Nathaniel
Cook
Dr. Karen Bernd
Translocation meets resistance: Characterizing herbicide resistance
in Chlamydomonas reinhardtii tip mutants
The global need for increased crop production has created a demand for effective, efficient herbicides that control unwanted plants. Detailed knowledge of molecular mechanisms that underlie the chemical/organism interaction would aid in the design of more effective and safer products. The photosynthetic algae, Chlamydomonas reinhardtii is particularly useful in the study of herbicides and herbicide resistance because of it is amenable to genetic and biochemical analyses and, unlike higher plants, non-photosynthetic Chlamydomonas mutants are viable if provided a carbon source. The tip1-1 mutant strain of Chlamydomonas is resistant to flumiclorac pentyl ester, an herbicide that is a PPO inhibitor. The long-term goal of this study is to characterize this resistance and provide evidence for a molecular model for resistance to PPO inhibitors. To achieve this goal 2 novel growth assays have been developed that allow rapid characterization of multiple strains under multiple growth conditions. These assays were used to determine baseline growth data for control and mutant strains and will be used to further characterize the degree and range of herbicide resistance provided by the tip mutations.
Courtney
S. Ewart
Dr. David Wessner, mentor
Molecular characterization of the mouse hepatitis virus receptor
In order for a virus to infect a cell, the virus first must come in intimate contact with the cell. Most often, this intimate contact is mediated by a specific interaction between a protein on the viral surface (viral attachment protein) and an integral membrane protein on the cell surface (receptor). The interaction between these two proteins not only allows the virus to attach to the host cell, but also often results in conformational changes that are necessary for entry of the viral particle into the cell. Previously, the discovery of a short region of the mouse hepatitis virus receptor (MHVR) that is necessary for mouse hepatitis virus (MHV) binding was reported. Using current molecular biology
David
Lamar, Suzanne Moore, and Annie Welsh
Dr. Mark Stanback, mentor
Nest site fidelity in Eastern Bluebirds: predator
vs. parasite avoidance
By nesting in cavities low to the ground, secondary cavity nesters increase the likelihood of detection by mammalian and reptilian predators. By reusing soiled nests, such birds presumably incur the costs of nest parasites. By experimentally varying these two factors, we tested the relative importance of each to nest site fidelity in Eastern Bluebirds. Previous research has demonstrated that Eastern Bluebirds avoid reusing soiled boxes (when provided with a second, clean box) but prefer to reuse successful nest boxes (if they are clean). With respect to nest height, bluebirds showed a significant preference for high (5 ft) vs low (4 ft) boxes for their first nests of the year, suggesting that they are sensitive to the vulnerability of their nest to predators. For second nests in 1999, we forced bluebirds to choose between their successful soiled box or a clean low box. If bluebirds are more sensitive to parasites than predators, one would expect birds to switch to clean low boxes. If birds are more sensitive to predation risk, they should reuse their soiled high nests. We found that bluebirds reused soiled high boxes significantly more often than they reuse soiled nests when given boxes of equal height. This suggests that both parasite and predator avoidance are relative to the quality of available nest sites.
Eastern Bluebirds as Environmental Indicators on North Carolina Golf Courses
Analysis of reproductive parameters of golf course nesting birds can provide valuable information on the biological effects of golfer and turf maintenance activities on course wildlife. Because eastern bluebirds (Sialia sialis) nesting on fairways feed their young on insects collected primarily on managed turf, they may be vulnerable to the chemicals used there. In 1999, we monitored 150 nestboxes in control habitat (hayfields and pastures) and 100 nestboxes on golf courses (25 on each of four courses) near Davidson, NC for first egg date, clutch size, hatching success, within-brood size disparity, nestling condition, and nest failure. We detected no significant differences in any of the above measures.
Mate Choice in Eastern Bluebirds: The Role of Condition
If female birds prefer mates of the highest genetic quality, but are constrained in their choice of partner by the choices of higher quality females, one would expect to observe a positive correlation between male and female condition within pairs. Alternatively, within-pair similarity could be due to the fact that paired birds live on the same territory and share parental duties. To address this, we measured eastern bluebird (Sialia sialis) condition during the chick-rearing phase using indices of current vs. past condition. Mass and hematocrit both reflect nutritional and physiological condition at the time of capture. Size-specific mass and bilateral asymmetry presumably reflect the condition of the bird during feather growth in the prior year. Mass and hematocrit showed significant correlations between male and female social mates. Feather-based indices showed no correlation. This suggests that much of the similarity of mated pairs may develop after pairing.
Shane
D. Lindsay and Jennifer L. Roberts
Dr. Michael Dorcas, mentor
Geographic variation in turtle populations in the Davidson, NC
area
Geographic variation in species over small spatial scales can often be attributed to habitat differences and can sometimes be linked to "habitat quality." We examined small-scale geographic variation in aquatic turtle populations among three ponds with varying degrees of cattle impact in the vicinity of Davidson, NC. We conducted a mark-recapture study to compare turtles among the ponds at community and population levels in addition to testing for morphological variation and differences in reproduction. We found considerable variation in species present and in relative abundances among species. Bottom dwelling turtles, mud turtles (Kinosternon subrubum) and snapping turtles (Chelydra serpentina), were absent from the pond with the highest cattle impact and mud turtles were most abundant at the pond with no cattle impact. Likewise, mud turtles were larger in all dimensions and their eggs were bigger at the pond with no cattle impact. We suspect that observed geographic variation may be due to habitat differences among the ponds, possibly varying levels of cattle use.
1999 Summer Research Fellows at Davidson
Hughes Summer Research Fellows '97
