Unless noted otherwise, all seminars are held
at 12 noon in Hollings Science Center, room 239.

Monday, September 7
Dr. Jacobus de Roode, Emory University   Website     
Research interest: the ecology and evolution of parasites, using butterflies and rodent malaria.

Virulence evolution in a protozoan parasite of monarch butterflies

[read abstract]
Why do parasites cause disease? Theory has shown that natural selection could select for virulent parasites if virulence is correlated with between-host parasite transmission. Because ecological conditions may affect virulence and transmission, theory further predicts that adaptive levels of virulence depend on the specific environment in which hosts and parasites interact. To test these predictions in a natural system, we study monarch butterflies (Danaus plexippus) and their protozoan parasite (Ophryocystis elektroscirrha).
     Our studies have shown that more virulent parasites obtain greater between-host transmission, and that parasites with intermediate levels of virulence obtain highest fitness. The average virulence of wild parasite isolates falls closely to this optimum level, providing additional support that virulence can evolve as a consequence of natural selection operating on parasite transmission. Our studies have also shown that parasites from geographically separated populations differ in their virulence, suggesting that population-specific ecological factors shape adaptive levels of virulence. One important ecological factor is the monarch larval host plants in the milkweed family. Monarch populations differ in the milkweed species they harbor, and experiments have shown that milkweeds can alter parasite virulence.
     Our running hypothesis is that plant availability shapes adaptive levels of parasite virulence in natural monarch populations. Testing this hypothesis will improve our understanding of why some parasites are more harmful than others, and will help with predicting the consequences of human actions on the evolution of disease.

Monday, September 14
Dr. Erin Dolan, Virginia Tech  Website     
Research interest: developing and providing tools to help the general public better understand genetics: designing programs and learning experiences that help students develop a deeper understanding of the applications and implications of biotechnology and the process of scientific inquiry.

Undergraduate level inquiry: Benefits and challenges of classroom-based research

Monday, September 21
Dr. Thomas Rainwater, Consultant 

Status and conservation of the critically endangered gharial (Gavialis gangeticus) in India

[read abstract]
The Indian gharial (Gavialis gangeticus) has been eliminated from much of its historic range and is listed as critically endangered by the IUCN (International Union on the Conservation of Nature). The National Chambal Sanctuary (NCS) in north central India is home to the largest remaining populations of gharials in the world, and the Chambal River provides critical habitat for other endangered species including Ganges river dolphins (Platanista gangetica), smooth-coated otters (Lutrogale perspicillata), red-crowned roof turtles (Batagur kachuga), mugger crocodiles (Crocodylus palustris), and numerous waterfowl and fish species.
     Between December 2007 and March 2008, approximately 110 subadult and adult gharials were found dead or dying in the NCS. The Chambal River is considered to be relatively pristine compared to India’s largest rivers; however, the available data suggest the cause of death was kidney failure, followed by visceral and articular gout, possibly resulting from exposure to an unidentified toxic chemical or mixture of chemicals. One hypothesis regarding the source of chemical exposure is that contaminated fish migrating into the Chambal River from its confluence with the highly polluted Yamuna River were consumed by gharials. Non-native tilapia (Oreochromis sp.) have been present for years in the Yamuna River, a drainage of the major urban cities Delhi and Agra, but have only recently moved into the NCS.
     In March 2009, we initiated a study to examine the health of tilapia in the Chambal River as a potential indicator of the influence of environmental pollution on wildlife fitness.  Specifically, we compared morphological indices used to assess fish health in tilapia collected in the Yamuna and Chambal rivers. Tilapia were collected from six locations along a putative gradient from an area of expected high pollution (Yamuna River) to an area of expected low pollution (Chambal River, ~ 240 km upstream from the Yamuna River). Morphological indices included condition factor (CF), hepatosomatic index (HIS), splenosomatic index (SSI), and gonadosomatic index (GSI).  CF was greater in tilapia from the Chambal compared to the Yamuna, and the CF improved within the Chambal as the distance upstream from the confluence with the Yamuna increased. HSI was greatest in tilapia from the Yamuna, whereas no differences were detected for SSI or GSI.
     These results support the hypothesis that environmental quality improves along a gradient from the Yamuna upstream into the Chambal River. Further analyses of contaminant burdens in tilapia along the same gradient are warranted to determine if this non-native species poses a serious threat to piscivorous wildlife as its range expands into new drainages.

Monday, September 28
Dr. Lisa Cunningham, MUSC  Website     
Research interest: the mechanosensory hair cells that are the sensory cells of the inner ear are responsible for transducing sound energy into neural signals. These cells are susceptible to death from noise trauma, aging, genetic disorders, and certain therapeutic drugs. The goal of work in our laboratory is to examine the molecules and signal transduction pathways that are involved in regulation of hair cell survival and death.

Life and Death in the Inner Ear: Heat Shock Proteins and Sensory Hair Cells

[read abstract]
Human hearing loss is often caused by death of mechanosensory hair cells that are the sensory cells of the inner ear. These cells transduce sound energy into neural signals. Hair cells are susceptible to death from noise trauma, aging, genetic disorders, and certain therapeutic drugs. Two primary classes of ototoxic drugs are the aminoglycoside antibiotics and the anticancer drug cisplatin. Hair cell death caused by these drugs is apoptotic, meaning the cell is activating an intrinsic program of cellular suicide.
    The goal of work in our laboratory is to examine the molecules and signal transduction pathways that are involved in regulation of hair cell survival and death. Recently we have shown that induction of heat shock proteins (HSPs) inhibits both aminoglycoside- and cisplatin-induced hair cell death. HSPs are evolutionarily-conserved molecules that are activated in response to cellular stress and can inhibit cell death in a large variety of systems. We are currently examining the molecular mechanism(s) underlying the protective effect of HSP induction in hair cells. Understanding these mechanisms will guide the development of therapies aimed at preventing hearing loss.

Monday, October 5
Dr. Derek Zelmer, USC, Aiken  Website     
Research interest: Among-scale interactions of population and community processes in aquatic systems, determinants of parasite community structure in aquatic vertebrates, transmission dynamics of parasites in lotic ecosystems.

Determinants of parasite community structure in freshwater fishes

Monday, October 12

FALL BREAK – no seminar scheduled

Monday, October 19
Dr. Robert Baldwin, Clemson University  Website     
Research interest: Conservation planning at multiple spatial and temporal scales (i.e., pool-breeding amphibian landscapes to ecoregions); effects of urbanization on amphibian and reptile communities; landscape ecology.

Conservation Planning for Pool-Breeding Amphibians

[read abstract]
Conservation planning occurs at multiple scales. My talk will examine several approaches I have taken with my colleagues from throughout North America for projects occurring at the continental, ecoregional, and local scales. GIS is used intensively at broad scales, but for pool-breeding amphibians at local scales field study must be integrated to make fine-scale decisions about allocating land for habitat for sensitive species, while still acknowledging the tremendous development pressure, in high-amenity areas. My talk will consist of three case studies using GIS data at the North American, Appalachian, and municipal scales for conservation planning, and will illustrate the particular problems with habitat conservation for species with complex life cycles, dependent upon wetlands as well as adjacent terrestrial habitats. I will make the case for integration of field and remote (i.e., GIS) studies, and for doing GIS only with a thorough understanding of the ecology of species whose habitat is being modeled.

Monday, October 26
Dr. Dana Nayduch, Georgia Southern University  Website     
Research interest: to investigate insect and microbe interactions. The current model is the housefly, bacteria and fungi; investigating housefly-microbe symbiosis from two perspectives: Housefly microbial biology; and housefly functional genomics.

Trash or treasure: How has living in sepsis shaped the house fly immune response?

[read abstract]
House flies (Musca domestica L.) eat, breed and thrive in septic environments that are teeming with microorganisms. As a result, flies often harbor pathogenic microbes in their digestive tracts and on their surfaces, yet they rarely succumb to disease.

Research in my laboratory focuses on the relationship between house flies and the bacteria they harbor, from the perspective of both parties in this symbiosis. We have examined the fate of several species of GFP-tagged bacteria in the house fly alimentary canal. The temporal and spatial fate of bacteria seems to be species-dependent, with some organisms being regurgitated in vomit, others being lysed early after ingestion, and still other species persisting and being excreted in feces.

Ingested bacteria face an onslaught of defense mechanisms in the house fly alimentary canal, including physical barriers (peritrophic matrix) and secreted humoral defenses (lysozyme and antimicrobial peptides; AMPs). An immune-stimulated adult housefly EST library was constructed and revealed several AMP genes of interest. The expression of several of these AMPs (attacin, diptericin, defensin, cecropin, sarcotoxin) was examined during both artificial and "natural" exposure to six species of Gram-negative or Gram-positive bacteria. Northern analysis showed that houseflies may have a species-specific and temporally-regulated AMP response to ingested bacteria, not previously observed in other insects. Interestingly, neither wild flies (not exposed to pure bacterial cultures, but also not microbe-free) nor flies fed heat-killed bacteria upregulated AMP expression. However, all life stages of house flies (larvae, pupae, adults) showed a constitutive expression of the peptidoglycan-digesting enzyme lysozyme. These data suggest that the house fly immune response may be tailored in a way that discriminates between threatening pathogens and benign commensals, and responds accordingly.

One proposed scenario is that physical barriers in the gut (the peritrophic matrix) and constitutive production of a broad-spectrum lysozyme both synergistically serve as a primary line of defense, while AMPs are produced only as needed when these other defenses are overwhelmed (either by the abundance or the type of microbe present). This unique immune repertoire may represent a level of specialization needed for a life of living in otherwise constant immune stimulation. Producing AMPs and other secondary responses only when needed could help conserve energy in flies by promoting metabolic efficiency and by deterring wasteful or unnecessary immune responses.

Monday, November 2
Dr. Gavin Naylor, The Florida State University  Website
Research interest: the mechanisms underlying biological diversification at both the organismal level and the molecular level. To discover how new traits arise and how genetic variation maps to phenotypic variation.

Metaphors in Molecular Evolution: Enlightenment in a Straight-Jacket

Monday, November 9
Dawn M. Roellig, University of Georgia Athens  Website
Research interest: vector-borne zoonoses (particularly those transmitted by ticks) and parasitic diseases.

Trypanosoma cruzi in the United States: Molecular characteristics and a host-gene dichotomy

[read abstract]
Trypanosoma cruzi, the causative agent of Chagas’ disease, is primarily a disease of humans in Central and South America. In the United States, autochthonous human cases have been reported and the prevalence in wild sylvatic hosts can be equally as high as in South America. T. cruzi is often characterized based on genotype and then biological characters, such as virulence, host predilection, and infectivity, correlated to the genotype group. Our findings indicate that only two genotypes (TcI and TcIIa) are present in the United States based on human, vector, wildlife, and domestic and captive exotic animal isolates. DNA sequencing of multiple gene targets has revealed genetic diversity in these isolates, and experimental infections of common sylvatic hosts indicate a host-strain dichotomy. In addition, experimental infections of laboratory mice indicate decreased virulence in these isolates compared with South American isolates. Collectively our research highlights genetic diversity in the region despite the presence of only two genotypes and in vivo biological characters that associate with these genotypes.

Monday, November 16
Dr. Chandrasekar S. Kousik, U.S. Vegetable Laboratory, USDA-ARS  Website
Research Plant Pathologist

Managing new and emerging diseases of watermelon

[read abstract]
Watermelon vine decline (WVD) is a new and emerging threat to watermelon production in southeast and west-central Florida and has caused more than $60 million in losses since 2004. The disease is caused by Squash vein yellowing virus (SqVYV, family: Potyviridae, genus: Ipomovirus) which is transmitted in a semi-persistent manner by whiteflies (Bemisia tabaci). Symptoms of WVD typically include a sudden decline of vines at harvest time, or one to two weeks prior to harvest and is capable of affecting fruit quality. So far only cucurbits have been determined to be hosts for SqVYV and the symptoms of vine decline have been observed only on watermelons. In surveys conducted in Florida over 40% of balsam-apple (Momordica charantia) plants collected from watermelon growing areas with previously reported cases of vine decline were found to be infected with SqVYV. Creeping cucumber (Melothria pendula) another common weed was also determined to a host for SqVYV. A combination of reflective plastic mulch with insecticidal treatments of neonicotinoid at transplanting followed by foliar spray of spiromefisen to manage whitefly populations significantly reduced WVD and incidence of fruit symptoms compared to un-treated plants that were on non reflective mulch. Applications of systemic acquired resistance inducers (SAR) in combination with insecticides also reduced the incidence and severity of WVD. We have identified several sources of resistance to SqVYV in the USDA germplasm. PI 500354 (Citrullus lanatus var. citroides), PI 386024 (C. colocynthis), and PI 459074 (C. lanatus var. lanatus) had significantly lower levels of WVD in the field studies compared with the highly susceptible commercial cultivars Mickey Lee and Crimson Sweet. Variability in the resistant reaction to SqVYV within these and other PI also was observed. Present recommendations for managing WVD include management of whitefly populations, removal of SqVYV reservoir hosts, and crop destruction soon after harvest.

Monday, November 23
T.B.A.

Monday, November 30
Dr. Timothy Sparkes, DePaul University  Website
Research interest: Aquatic Biology, Behavioral Ecology of Invertebrates and Fishes

Factors influencing mating patterns in the stream-dwelling isopod Lirceus fontinalis: ecology, physiology and behavior

[read abstract]
I will present a summary of several years of research on the mating behavior of the crustacean isopod Lirceus fontinalis. This research has used an integrative approach to examine the interacting effects of ecology and physiology on mating behavior and mating patterns and has yielded some unique insights. The stream-dwelling isopod L. fontinalis is a common detritivore in streams around Lexington, Kentucky. Mating behavior is common during the spring, and involves a precopulatory mate guarding phase, during which the male carries the female beneath him for several days. The mate guarding phase is followed by female molt and copulation. Prior to mating, male and female C. intermedius engage in conspicuous struggles (mating contests) during which both male and female choice occurs. Males exhibit preferences based on female molt status and females exhibit preferences for males based on physical condition. At the population-level, mating is size-assortative (SAM) with large males pairing with large females and small males pairing with small females. Patterns of SAM are highly variable among populations and variation in SAM correlates with population differences in local ecology. Isopods from permanent streams exhibit strong patterns of SAM, whereas isopods from intermittent streams exhibit weak patterns of SAM. I will propose explanations for the pattern of variation in SAM observed in these populations.

Monday, December 4
Dr. Pawel Michalak, University of Texas, Arlington  Website  |  Lab Website
Research interest: genomics from an evolutionary perspective; the evolution of gene and genome regulation patterns.

Genomic insights into the origin of new species