Ecology and evolutionary biology.

Chair: Clifford Ochs, University of Mississippi 

Vice-chair: Tom Mohrman, University of Southern Mississippi

THURSDAY MORNING

Meeting Room 7

8:30 Introduction to Session

8:45 THE INFLUENCE OF TESTOSTERONE AND MIGRATION ON THE RELAPSE OF PLASMODIUM RELICTUM IN EXPERIMENTALLY INFECTED GRAY CATBIRDS (DUMETELLA CAROLINENSIS)

Amanda Jo Williams (1*), Jennifer C. Owen (1), and Mary Garvin (2), (1) University of Southern Mississippi, Hattiesburg, MS 39406 and (2) Oberlin College, Oberlin, OH 44074

Birds chronically infected with avian malaria often experience relapse in the spring, but the mechanism behind this phenomenon is poorly understood. Two possible triggers of spring relapse are the elevation of testosterone (T) associated with the breeding season and stress from spring migration. To investigate the individual and synergistic effects of these variables, I will use the malaria parasite Plasmodium relictum and gray catbirds (Dumetella carolinensis). Fifty male hatch year gray catbirds (GRCA) will be infected via intramuscular inoculation, and ten uninfected birds will serve as negative controls. Spring migration will be simulated by photoadvancing birds in January to induce migratory restlessness. Testosterone will be elevated to levels observed during the breeding season with surgically inserted implants. Birds will be equally divided among the following six treatments: migratory with T-implant, migratory with placebo implant, non-migratory with T-implant, non-migratory with placebo implant, non-migratory with no implant, and negative controls (non-migratory with no implant). Prevalence and intensity of relapse will be monitored by microscopy of stained blood smears. I predict that relapse will occur at a greater rate in treatments undergoing migration and / or receiving T, with the greatest prevalence and intensity in the treatment receiving both.

9:00 VARIATION IN WHITE BLOOD CELL COUNT IN RELATION TO INTENSITY OF MALARIA INFECTION IN A PASSERINE BIRD

Ashley DeCoux*, Amanda Jo Williams, and Jennifer C. Owen, University of Southern Mississippi, Hattiesburg, MS 39406

The gray catbird (Dumetella carolinensis), a migratory passerine bird, is known to be infected with the blood parasite Plasmodium relictum. Poultry studies demonstrate that white blood cells (WBC), particularly lymphocytes, increase in response to infection by Plasmodium spp. As part of a larger study, female catbirds will be infected with a frozen stabilate of P. relictum that will be passaged three times to increase parasite virulence. The goal of the present study is to determine the effect of multiple passages on the intensity of P. relictum infections and to assess the catbirds' immune response to the parasite infection by measuring WBC counts. Hatching year catbirds were captured in Ohio and blood was collected immediately following capture to obtain baseline data on parasite load. Birds were housed in individual cages located in University of Southern Mississippi's Biodafety Level 3 Animal Research Facility. After infection, birds will be bled daily until parasitemias become patent and every third day thereafter until parasitemias are no longer detectable by microscopy. To identify and count parasites and WBCs, a thin smear of blood will be made on a glass slide and stained using Hema-3 stain. Absolute counts of parasites and WBCs will be performed under oil immersion. We predict a positive correlation between parasite intensity and WBC count.

9:15 USE OF DREDGE MATERIAL ISLANDS BY PASSERINE MIGRANTS: IMPLICATIONS FOR CONSERVATION AND RESTORATION OF STOPOVER HABITAT

Sarah Wheeless* and Frank R. Moore, University of Southern Mississippi, Hattiesburg, MS 39406

Conservation of habitat for Nearctic-Neotropical migratory birds should include not only tropical wintering and temperate breeding grounds, but also habitats in which birds rest and refuel during migratory journeys. Quality stopover sites are crucial to the survival of migratory birds, especially when sites are adjacent to large geographic barriers (e.g. Gulf of Mexico, Atlantic Ocean). Dredged material islands, many of which are located on the northern coast of the Gulf of Mexico, have traditionally been maintained as habitat for colonially nesting waterbirds or threatened and endangered species (Landin 1986). We suggest that these islands may aid in local and regional conservation of stopover habitat for migratory landbirds. Research was conducted on the Greenwood Island Mitigation Site, a dredge material island on the Mississippi Gulf Coast Gulf in Pascagoula, Mississippi. Transect surveys were conducted during the spring and fall migratory periods of 2004 and 2005. Over forty species of Nearctic-Neotropical landbird migrants were documented on the site. Passerine migrants were more often found in shrub habitats, while waterfowl and wading birds were distributed throughout the wetland and marsh habitats. On Greenwood Island and other dredge material islands, restoration efforts can include both the maintenance of marsh and wetland habitats as well as the establishment of native shrubs and fruiting vegetation, thereby providing quality habitat for both waterbirds and landbird migrants.

9:30 USE OF WEATHER RADAR IN STUDIES OF BIRD MIGRATION IN THE SOUTHWEST: OVERCOMING RADAR BEAM OBSTRUCTION

Rodney Felix*, Robert H. Diehl, and Frank R. Moore, University of Southern Mississippi, Hattiesburg, MS 39406

Much of what is known about migrating birds in North America has been inferred from studies in the eastern United States; little effort has been spent investigating migration west of the American Great Plains. My work is part of an effort, in collaboration with the U.S. Geological Survey, to understand flight behavior and habitat use during migration across the southwestern United States. The large scale of this study and nocturnal habits of migrating birds make traditional field-based data collection techniques logistically impractical. Alternatively, weather radar technology has proven valuable in studies of bird movement and is well suited for this research--it can collect data across large spatial scales, operate continually, and automatically archive data for no-cost retrieval by the public. Unfortunately, mountainous terrain (which is common throughout the Southwest) can interfere with or block a radar's beam, and so contribute to inaccurate data collection. As a prerequisite for using radar data to address biological questions associated with migration in the Southwest, I am developing GIS-based methods for establishing where the data most reliably quantify migrating songbirds. By combining in a GIS archived weather radar data of migrating birds with models of how terrain features may interfere with a radar's beam, I have generated filters that conservatively determine which data are least effected by radar beam obstruction due to terrain. This represents a critical early step to preparing weather radar data for use in addressing biological questions important to understanding migration through the Southwest.

9:45 THE REGULATION OF GENDER EXPRESSION IN CERATOPERIS RICHARDII GAMETOPHYTES

Robert Hamilton, Mississippi College, Clinton, MS 39058

There are two basic morphologies among gametophytes of Ceratopteris richardii, the large meristic hermaphrodite and the small ameristic male. In vitro studies have indicated that the small male morphology is characteristic of multispore cultures, with single-spore cultures resulting in large hermaphrodites. The pheromone antheridiogen is known to cause the induction of the small ameristic male phenotype in C. richardii gametophytes. We investigated the effect of competition for nutrients on gender expression and the timing of the appearance of morphological changes associated with the antheridiogen response. Competition for nutrients had no effect on gender expression in our experiment. Morphological changes associated with the antheridiogen response were apparent upon the emergence of a 2 dimensional gametophyte from the spore wall. If the antheridiogen response is derived from competition for nutrients, there is no apparent remnant of an effect of competition for nutrients on gender expression in C. richardii. The appearance of a size dimorphism that is associated with the antheridiogen response in the earliest stages of gametophyte culture suggests that the factors that trigger the antheridiogen response begin to affect gametophyte development at the earliest stages.

10:00 Break

10:30 TEMPORAL AND SPATIAL VARIATION OF METHANE (CH4) EMISSION IN A SPRING-FED FORESTED WETLAND

Hong-Suk Koh, University of Mississippi, University, MS 38677

Methane emission rates from a spring-fed forested wetland in northern Mississippi were measured during the growing months (May-September 2005) using a field chamber method. There were significant differences in emission rates from the four different habitats in the wetland: submerged vegetation site, emergent vegetation site, seasonally flooded forest site, and upland forest site. The highest emission rates (average 19.27 mg CH4/m2/hr) were recorded in June and July in the submerged vegetation site. The lowest emission rates (average 3.24 mg CH4/m2/hr) were observed in May and September in the seasonally flooded forested site where water was drained. Methane consumption occurred at the upland forest site during all studied months (average -3.00 mg CH4/m2/hr), suggesting that forest soils function as sinks of atmospheric methane. Methane emission rates were positively correlated with soil water content, standing water depth, and soil organic matter content. The movement of methane from anaerobic sediments through emergent plants into the atmosphere was found to provide a significant pathway for the emission of methane. Chambers enclosing plants had higher emission rates than plant-free chambers (controls) in the two dominant emergent species (Festuca spp. and Hydrocotyle umbellata L.) of the wetland. Positive correlations of methane emission rates with plant biomass and stem density indicate that vascular emergent plants play an important role as conduit of methane transport from the sediment to the atmosphere.

10:45 EFFECTS OF THE LIGHT ENVIRONMENT ON PRODUCTION OF BACTERIOPLANKTON AND PHYTOPLANKTON UNDER VARIOUS DEGREES OF NUTRIENT-LIMITATION

Clifford A. Ochs* and Fortune E. Ogbebo, Department of Biology, University of Mississippi, University, USA, 38677

In nutrient limited lakes, there is likely to be competition for nutrients between heterotrophic bacterioplankton and phytoplankton. If, as studies indicate, bacterioplankton and phytoplankton have differential susceptibilities to photoinhibition, the degree of nutrient competition will vary with light intensity and spectral composition. In summer 2003 we conducted a field experiment and laboratory experiments to test the hypothesis that the light environment interacts with the chemical environment to differentially impact phytoplankton and bacterioplankton growth rates. The field experiment was conducted in Oxford, MS using 18-liter mesocosms under natural sunlight, with UV blocked or not, for seven days. The lab experiments were conducted using lamps allowing us to better control intensities of UVB, UVA, and PAR. Organic carbon and phosphorus were supplied to create either C or P-limitation, or neither C nor P limitation. In both kinds of experiment, there were significant main and interaction effects of UV and the UV-nutrient combinations on phytoplankton and bacterioplankton production. The magnitude of these effects on bacterioplankton and phytoplankton were unequal and varied with time of incubation. Our results suggest that the light environment can influence competitive interactions between phytoplankton and bacterioplankton.

11:00 CONTROLLING FACTORS OF SUBMERSED AQUATIC VEGETATION (SAV) IN GRAND BAY NATIONAL ESTUARINE RESEARCH RESERVE (NERR), MISSISSIPPI

Hyun Jung Cho* and Christopher A. May, Jackson State University, Jackson, MS 39217 and Grand Bay National Estuarine Research Reserve, Moss Point, MS 39562

Healthy beds of Submersed Aquatic Vegetation (SAV) protect shoreline, improve water quality, and provide food and nursery habitat for aquatic organisms. The extensive wildlife habitat of Grand Bay National Estuarine Research Reserve (GBNERR) offers educational, research, and recreational opportunities. However, little is known about factors that control and limit the SAV distribution and growth in GBNERR. We surveyed the SAV depth distributions along transects at five sites in June and October 2005 to assess the current areal coverage, species composition, and seasonality of the SAV beds. SAV growth was restricted to 1.3 m water depth. We will use our biweekly monitored PAR measurements to compute the annual mean light level at the maximum depth to find the SAV light requirement in GBNERR. The species composition differed between summer and the fall. Ruppia maritima dominated in summer surveys and Halodule wrightti replaced R. maritima in most of the sites by fall. Impacts of Hurricane Katrina were greater in areas exposed to the direct sedimentation. Sedimentation caused by storms is reported to directly bury SAV beds, but it also stimulates SAV growth in some cases by depositing new propagules and seeds in the transported sediment. Future surveys will explain the long-term effects of the recent hurricanes on Grand Bay NERR SAV.

11:15 EFFECTS OF MALATHION ON CHOLINESTERASE ACTIVITY IN BLUE CHANNEL CATFISH (ICTALURUS FURCATUS)

Winfred Aker*, Xiaoke Hu, Yuquan Zheng, and Huey-Min Hwang, Jackson State University, Jackson, MS 39217

The use of insecticides to protect crops from the ravages of insects is practiced worldwide. Organophosphates (OPs) may exert their toxicity on insect pests by inhibiting the critical body enzyme cholinesterase. Unfortunately, they cannot discriminate in the exercise of their toxicity against unintended target organisms including humans. Therefore, an assessment of the danger posed to unintended targets is warranted. Of particular concern to aquiculture farmers in the state of Mississippi is the impact upon the catfish farming industry from OPs. Cholinesterases have been widely used as a biomarker for the assessment of exposure to organophosphate insecticides. In this study, Blue Channel Catfish (Ictalurus furcatus) were exposed to the following concentrations of the organophosphate insecticide Malathion: 0, 0.5, 1.0, 2.0, 2.5, 5, 7, 10 and 15ppm. After 96 hours, the surviving catfish were sacrificed after using 0.1% 2-Phenoxyethanol as anesthesia. Brain, liver and muscle tissues were extracted and homogenized in pH 8.0 phosphate buffer. The supernatant of the homogenization was analyzed for cholinesterase activity using the Ellman Method. We hypothesized that all cholinesterases are inhibited after exposure to malathion. The results showed that the [LC.sub.50] for the fingerling Blue Channel Catfish is between 10 and 15ppm. The actylcholinesterase activity was significantly inhibited in brain tissue especially at the concentrations>5ppm. The butyrylcholinesterase activity in muscle and liver tissues was not significantly inhibited. This research was supported by the U.S. Department of the Army Research and Development grant # W912H2-04-2-0002 to Jackson State University.

11:30 ENVIRONMENTAL VARIABLES AFFECTING ANT (FORMICIDAE) COMMUNITY COMPOSITION IN FOUR HABITATS IN MISSISSIPPI

JoVonn Hill*, Richard L. Brown, and Joe A. MacGown, Mississippi State University, Mississippi State, MS 39762

Numerous species of ants have habitat preferences and respond quickly to disturbances to their environment, making them valuable for habitat monitoring. However, the effects of various environmental variables remain uncertain. This study investigates the relationship of ant community composition to various habitat characteristics by comparing ant communities and 12 environmental variables across four habitat types in Mississippi. The four habitat types include pasture, prairie, and oak-hickory forests in the Black Belt and forests in the Flatwoods physiographic region. Ants were sampled using pitfall traps, litter sampling, baiting and hand collecting. NMS and ANCOVA both revealed three distinct ant communities (pasture, prairie, and "forests") between the four habitat types based on species composition and mean ant abundance per habitat type. Principal component analysis (PCA) partitioned the environmental variables into four axes with eigenvalues>1. Axis 1 divides the site into two types (open and forests), while axis two separates pasture from prairie. Multiple regression models using the four significant PCA axes revealed that total species richness was significantly affected by variation in the first two PCA axes. Forested sites supported approximately nine more species of ants than prairies, and 21 more than pastures (p=.0001). Comparisons of ant functional group abundance were also made between the four habitat types with multiple regression models to investigate how the environmental variables affected certain groups of ants.

11:45 Divisional Business Meeting