Rapid subsidence and eustatic sea level rise are leading to increased flooding and perpetually waterlogged soils along the Gulf Coast. This study addresses the impact of this environmental change on coastal Louisiana bottomland hardwood forests. I employed a space-for-time substitution to compare seed banks, seedling banks, and seed rain in two sites of different hydroperiod, and to predict how small increase in hydroperiod may affect forested wetland community composition and dynamics Within terrestrial ecosystems, seed banks respond to disturbances by providing individuals for regeneration. In this study the wetter ('swamp') site's seed hank was more dense and species rich than the drier ('ridge') site's. Herbaceous species dominated both sites' seed banks. Tree and shrub seeds were most numerous and species rich in the ridge site, suggesting regeneration of the woody community requires a seed bank like that encountered in drier soils. Thus, as hydroperiod Continue to increase, seed of woody species will become unavailable for disturbance response Like seed banks, seedling hanks are active in disturbance response. While the cumulative number of seedlings censured over two years was equivalent at both sites, the ridge site hod greater seedling density, longer mean seedling lifespan, and greater seedling survivorship. In both sites, woody seedlings were denser and more species rich than herbaceous seedlings. Although a severe drought caused short-term decreases in seedling density, health, and leaf number regardless of site, the expected increase in hydroperiod will have long-term implications Lastly, I used the seed bank, seedling bank, and seed rain data to construct site-specific static life tables for selected woody species and life form groupings. These illustrate how individual species would respond to increases in hydroperiod. While some woody species, including Acer rubrum and Brunnichia ovata, will benefit from more hydric soils, most, including Celtis laevigata and Liquidambar styraciflua, will decline This study indicates that environmental changes already underway will lead to a loss of coastal plain bottomland hardwood forests as communities shift to species adapted to greater hydroperiod. If these trends are allowed t0 continue unabated, an eventual loss of all woody species, and therefore coastal forested wetlands, is expected / acase@tulane.edu

acase@tulane.edu

This comparative study of the reproductive success of populations of I. pes-caprae around the Gulf of Mexico involved determining which insect species were flower visitors of I. pes-caprae at each study site, and which of the flower visitors were the effective pollinators in Yucatan. The distance pollen was carried was measured with the use of fluorescent powder to determine the impact of pollen flow on the breeding system of this self-incompatible species. Exclusion experiments were carried out in order to investigate the effect of ants on the reproductive success of I. pes-caprae and the relationship of the plant species with the seed predator Megacerus leucospilus. Measurements of morphometric traits of greenhouse plants grown from seed produced by populations around the Gulf of Mexico and the Caribbean were made to support data on gene flow. Population parameters were measured in order to compare populations from different areas. Crosses were made among plants from three populations in order to identify incompatibility groups and to obtain data on the type of incompatibility that was operating in the species / acase@tulane.edu

The factors limiting bird populations remain poorly understood, but evidence suggests non-breeding season events are important. I investigated the non-breeding ecology of resident and migrant forest landbirds during the annual dry-season in low-quality scrub and high-quality shade-coffee plantation habitat in Jamaica. Over four years (2002-2005), I studied the behavior, physiology, and population dynamics of birds in response to variation in dry-season food supply. In this system, I conducted the first landscape-scale food manipulation for tropical resident and wintering migrant birds. Plot-level supplementation and reduction altered food supply to a biologically significant degree in each year. Precipitation and food supply decreased in successive years creating a natural experiment in parallel to manipulations. For resident birds, most species had higher abundance and several had higher persistence following food supplementation. Manipulations did not cause changes in resident bird body condition. For Bananaquit (Coereba flaveola), food supplementation resulted in higher proportion of individuals in breeding condition. For migrants, I focused on the Ovenbird (Seiurus aurocapilla), a small monomorphic ground-forager. Multiple body condition indices responded to variation in food supply. However, food manipulation did not affect over-winter persistence or annual survival. Relative to birds in poor-habitat, Ovenbirds in high-quality habitat maintained optimum body condition, presumably to mitigate the tradeoff pressures of starvation and predation. In poor habitat, food constraints inhibited mass regulation and possibly delayed migration. Annual variation in spring migration departure timing corresponded to patterns of climate (and thus food). Most birds were territorial with a small home range containing roosts. Floaters occupied relatively large areas and comprised 8-16% of the population. The two classes of space use responded differently to changes in food supply: Floaters were better able to respond to shifts in food availability and had better body condition in low food situations. Food reduction did not induce sedentary individuals to adopt floater behaviors. I found no evidence of sex-based dominance relations in Ovenbirds. This study helps explain mechanisms by which bird populations respond to resource availability, and suggests that food is a primary driver of non-breeding season population limitation in seasonal tropical forests, at least on the Caribbean islands / acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

Interrelationships and possible hybridization between the shiners (CYPRINIDAE) Notropis lutrensis and N. venustus (subgenus Cyprinella) were studied in Bayou Pierre, Mississippi. Three approaches were used to evaluate these interrelationships. The first approach consisted of discriminant analysis of meristic and morphometric characters to identify parental and possible hybrid individuals in preserved specimens. This discriminant function separated the two reference N. lutrensis and N. venustus groups with 100% accuracy. An analysis of quarterly fish collections at eight localities showed a variable frequency of apparent hybrid individuals with an average of 13.7% The second methodology consisted of discriminant analysis for the separation of the above three groups on the basis of physico-chemical parameters. This approach was used to estimate niche overlap and separation between parental and hybrid clusters. The results showed the apparent hybrid group to be intermediate between parental groups, and Notropis lutrensis and N. venustus to have a niche overlap of 22.3%. Separation of the groups was primarily based on turbidity, apparent color, and the depth relative to width of the collecting site The final approach consisted of electrophoretic analysis to investigate genetic structure in Notropis collections and to explore possible genetic introgression between Notropis lutrensis and N. venustus. Comparison of proteins from allopatric and sympatric populations suggested likely gene introgression into N. venustus from N. lutrensis at several presumed genetic loci (CK, S-Mdh-2, Got-2) in the Lower Mississippi drainage. The occurrence of hybridization and introgression is also supported by the higher levels of genetic variability in Lower Mississippi N. venustus compared to levels in allopatric populations Hybridization between the two species is suggested as the origin of Gibbs' (1957) 'Red-Lower Mississippi' race of N. venustus. There is also evidence of gene introgession into N. lutrensis from N. venustus, although results are less certain due to higher background levels of genetic variability in N. lutrensis Although the three analytical approaches suggest a variable level of hybridization and gene introgression in Bayou Pierre, evidence indicates that Notropis lutrensis and N. venustus are generally distinct from each other in areas of sympatry, and are associated with specific allelic combinations. This distinctness suggests selection for the maintenance of certain gene complexes, and the specific validity of N. lutrensis and N. venustus. Hybridization in Bayou Pierre appears to be related to habitat alteration, increased turbidity, and to generalized breeding behavior in the two species Notropis camurus, a common member of the subgenus Cyprinella in Bayou Pierre, was also compared to its congeners. Electrophoretic evidence suggests that the species is quite distinct from both N. lutrensis and N. venustus, although it is closer genetically to N. venustus. A low frequency of hybridization occurs between N. camurus and N. venustus, although there is no apparent genetic introgression occurring / acase@tulane.edu

Ciliated protozoa comprise a diverse and quantitatively important component of salt marshes, especially in pools where microorganisms will tend to accumulate at the air-water and mud-water interfaces. The purpose of this study was to use artificial substrates as initially barren 'islands' and examine the colonization process in hopes of gaining a better understanding of the dynamics of the populations in these regions Mud from three different locations in the salt marsh near Leeville, La. was collected and placed in plastic pans in the laboratory. An overlying layer of seawater was added. Small nylon mesh grids (1.5 cm('2)) were placed parallel to the surface, either directly on the mud or just under the air-water interface. One grid (colonization grid) was collected and examined every two days for a period of three weeks. All ciliates on the grid were identified and counted. Additionally, a clean grid (invasion grid) was placed in the system each collection day and examined the next. These invasion grids gave an indication of the types and numbers of ciliates invading all grids over the interval between collections. Various physicochemical parameters were monitored Generally, community development follows the MacArthur-Wilson equilibrium theory. A dynamic equilibrium is attained with the species composition changing over time. There is a distinct succession of species from surface feeding forms to suspension feeding forms. The species composition and equilibrium number are also dependent on the origin of the mud. The invasion grids indicate that some species are excluded from the colonization grids, some are surviving on the colonization grids by a high invasion rate, still others are reproducing on the grids. Statistical analyses of association coefficients indicate the presence of species complexes The results of this study show that these artificial substrates do not just accumulate a random sampling of organisms, but that species interactions, environmental conditions and length of invasion all affect the developing 'island' community / acase@tulane.edu

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3273. Adviser: Edward J. Heske. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 50-61). Available also in a digital version from Dissertation Abstracts.