Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Bibliography: leaves 213-217.

Thesis (M.A.)--University of West Florida, 2008. / Title from title page of source document. Document formatted into pages; contains 138 pages. Includes bibliographical references.

Urbanization is accelerating in the United States and is contributing to fragmentation of natural habitats, causing changes in species composition and declines in native species. Human population growth in Orlando is typical of growth in the southeastern United States and throughout the range of cypress (Taxodium distichum). Orlando has numerous isolated cypress wetlands, called cypress domes, and many remain among the current urbanized area. This makes Orlando ideal to study the effects of urbanization on cypress domes. Specifically, I tested how urbanization and its effects on fragmentation, hydrology, and fire regime) affected (a) the numbers and spatial pattern of cypress domes in central Florida and (b) the recruitment of cypress within cypress domes. Analysis of historical loss found over 3,000 cypress domes identified in images from1984, of which 26% were lost or degraded (i.e., no longer cypressdominated) by 2004. Due to changed land use, many remaining cypress domes, formerly surrounded by natural lands, have become surrounded by urban lands causing spatial clustering and homogenization. Surprisingly, I found that both natural and urban cypress domes showed lower recruitment than agricultural cypress domes, where the natural fire regime has not been altered. The probability of cypress recruitment in cypress domes urbanized for more than 20 years is very low. Previous to that, cypress tends to recruit on the edge of cypress domes where there is less competition and hydrological conditions are more favorable. I estimate that only ~50% of the current cypress domes are recruiting and the existence of those wetlands are tied to the lifespan of the current adults. By 2104, I estimate that ~89% of the cypress domes currently recruiting will fail to recruit. I believe that reducing urban sprawl and restoring the natural fire iii regime to natural cypress domes will mitigate the current fate of cypress domes. Without this, cypress in isolated wetlands in central Florida, and providing Orlando urbanization is typical, throughout urbanized areas of the range, could be at risk. Cypress in urban areas will be then relegated to riparian zones and with unknown consequences for the species that utilize the former cypress dome habitat

Allocation of assimilated carbon amongst plant metabolic processes and tissues is important to understanding ecosystem carbon cycles. Due to the range of spatio-temporal scales and complex process interactions involved, direct measurements of allocation in natural environments are logistically difficult. Modeling approaches provide tools to examine these patterns by integrating finer scale process measurements. One such method is root:shoot balance, where plant growth is limited by either shoot activity (i.e. photosynthesis) or root activity (i.e. water and nutrient uptake). This method shows promise for application on frequently disturbed systems which perturb aboveground biomass and thus create imbalances in root and shoot activities. In this study, root:shoot balance, allometric relationships and phenological patterns were used to model carbon allocation and growth in Florida scrub oaks. The model was tested using ecosystem gas exchange (i.e. eddy covariance) and meteorological data from two independent sites at Merritt Island National Wildlife Refuge, FL which experienced two different types of disturbance events: a prescribed burn in 2006 and wind damage from Hurricane Frances in 2004. The effects of the two disturbance events, which differed greatly in magnitude and impact, were compared to identify similarities and differences in plant allocation response. Model results and process-based sensitivity analysis demonstrated the strong influence of autotrophic respiration on plant growth and allocation processes. Also, fine root dynamics were found to dominate partitioning trends of carbon allocated to growth. Overall, model results aligned well with observed biomass trends, with some discrepancies that suggest fine root turnover to be more dynamic than currently iv parameterized in the model. This modeling approach can be extended through the integration with more robust process models, for example, mechanistic photosynthesis, nitrogen uptake and/or dynamic root turnover models.

Subspecific taxonomic designations solely based on morphological characters can often lead to erroneous assumptions about the evolutionary history of populations. This study sought to investigate evolutionary questions and conservation implications associated with morphological subspecific designations of island populations. To this end, I focused my attention on the Lower Keys of Florida, a unique chain of islands with well-known geologic history and rich in endemic, endangered subspecies. I employed genetic analyses to evaluate historical variation and contemporary restriction of gene flow between the endangered Lower Keys marsh rabbit (Sylvilagus palustris hefneri) and its sister mainland taxa. A Bayesian phylogeny using 1063 base pairs of the mitochondrial cytochrome b gene did not recover reciprocal monophyly of the three named subspecies, and a 95% statistical parsimony haplotype network showed haplotypes being shared among subspecies. Furthermore, clustering analyses using 10 microsatellite loci identified a break within the Lower Keys, separating the western Lower Keys from the island of Big Pine Key. Surprisingly, Big Pine Key grouped with mainland populations and exhibits higher genetic diversity than the western Lower Keys islands. These unexpected findings suggest either a stepping-stone colonization pattern or recent gene flow between the mainland and Big Pine Key via natural dispersal or undocumented man-mediated transfers. Although these results suggest that subspecies designations within S. palustris are unwarranted, this study supports the designation western Lower Keys population as a discrete unit of conservation with regard to both DPS and ESU criteria. The importance of using several lines of evidence to uncover the evolutionary history of populations and implications for the conservation of island populations are discussed.

No description available.

No description available.

No description available.

No description available.

No description available.