Current projects in the lab fall into three general areas:
1. Biology and impacts of invasive species
Biological impacts of kudzu (Pueraria montana). Kudzu is notorious for overgrowing native vegetation, but surprisingly little work has been done on how shading and soil nitrogen enrichment affect the diversity of native plant communities. Ph.D. student Gina Profetto is comparing vegetation and soil and water characteristics at invaded, control, and removal sites to quantify these impacts and determine how long they last after kudzu removal.
Genetics of contemporary and historical populations of water hyacinth (Eichhornia crassipes). Hyacinth was introduced to North America at the 1884 World’s Fair in New Orleans, and has since spread throughout much of the southeast and Mississippi River basin. It is commonly assumed that North American populations are genetically homogeneous descendants of a single clone, but there has been abundant opportunity for selection to produce genetic differentiation (repeated herbicide spraying, colonization of cold temperate habitats) since introduction. M.S. student Elliot Weidow is using AFLPs to study genetic structure of modern populations on the Gulf Coast and compare them to herbaria collections dating back to the early 20th century to determine how much genetic diversity currently exists and how it may have changed since introduction.
Reproductive biology of Chinese tallow tree (Triadica sebifera). Tallow individuals vary widely in their relative investment in male and female reproduction, and those that invest heavily in seed production may be of particular importance in population growth and colonization of new habitats. M.S. graduate Courtney Babin has shown that this variation is not related to size, suggesting that trees may instead respond to spatial and temporal resource availability or to the cost of reproduction. We are now beginning a long term project to relate diameter growth and reproductive investment over several years to the availability of nutrients, moisture, and light, in order to determine the reasons for variable sex allocation.
2. Population biology and management
Effect of habitat quality on reproduction in the Mississippi sandhill crane (Grus canadensis pulla). The Mississippi sandhill crane is a federally endangered, non-migratory population in coastal Mississippi that is largely maintained through release of captive-reared individuals due to poor reproduction in nature. In an effort to understand the reasons for poor recruitment, previous graduate projects have analyzed the current genetics of the population, predator pressure, and developed a habitat suitability map of the Mississippi Sandhill Crane National Wildlife Refuge. Ph.D. Student Henry Wooley is now studying the link between habitat quality and success in egg production, chick survival, and fledging on different nesting territories.
Anti-predator conditioning for costume-reared sandhill crane chicks. A recent analysis of the behavior of cranes nesting on the Mississippi Sandhill Crane National Wildlife Refuge has shown that few parents recognize or respond appropriately to nest predators. We have hypothesized that captive-reared cranes released on the refuge lack opportunities to acquire appropriate behavior through social learning from parents and other cranes. We are working with the Audubon Nature Institute Species Survival Center to train costume-reared crane chicks to recognize predators and learn to defend nests.
Manatee (Trichechus manatus) distribution in Lake Pontchartrain. Manatees are often found in Lake Pontchartrain and nearby areas on the northern Gulf Coast, but their seasonal occurrence and environmental preferences are still poorly known. M.S. student Rebecca Callaway is beginning a systematic study of manatee distribution in Lake Pontchartrain using watercraft and drone surveys. She will also measure environmental parameters to determine how manatee distribution is related to water quality.
3. Insect behavior and functional ecology
Morphological and behavioral plasticity in Melanoplus differentialis grasshoppers. The differential grasshopper is a generalist herbivore at the population level but is often individually specialized, providing a model system for understanding the evolution of generalized and specialized feeding strategies in insects. We are currently investigating plasticity in behavior and morphology in response to diet, and M.S. student Austin Culotta recently completed a study of the effects of hard and soft diets on morphology.
Nuptial hemolymph feeding by female Eunemobius carolinus crickets. Sexual selection drives males of many species to provide nuptial gifts to females as an inducement to mate, and in addition to providing nutrient-rich spermatophores, Eunemobius carolinus males allow females to chew on and imbibe hemolymph from tibial spines during mating. M. S. student Austin Culotta has begun a new project to determine the effects of hemolymph feeding on female and male fitness.