MEES Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/19655
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Item Genetic Differentiation of Selected Eastern Box Turtle (Terrapene carolina) Populations in Fragmented Habitats, and a Comparison of Road-based Mortality Rates to Population Size(2009) Hagood, Susan; Adams, Lowell; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The decline of eastern box turtle populations is associated with habitat loss and fragmentation, lack of recruitment into breeding populations, removal of individuals from the wild for pets, and road mortality. Box turtle populations in many areas of the eastern United States may effectively be isolated as high traffic volumes on roads adjacent to turtle habitats prevent successful dispersal. If so, populations surrounded by heavily used roads may be less genetically diverse than those in relatively intact habitats. I investigated whether populations in three Montgomery County, Maryland parks that were surrounded by roads were genetically differentiated relative to populations in two larger habitats in Maryland's Prince George's and Anne Arundel counties. Sampling was conducted between 2005 and 2008. I used 10 microsatellite markers to compare these populations, and sampled in an additional five sites (two in Maryland, and one each in Pennsylvania, the District of Columbia, and Florida), to better assess population structure. I found little evidence of genetic differentiation among central Maryland populations regardless of the extent of isolation. I attribute these findings to the slow rate of change in turtle evolution; the observed similarities in genetic diversity may reflect past rather than present gene flow. I found moderate to great differentiation in populations separated by substantial distances. To determine whether road mortality exceeds additive mortality levels believed to be a threat to population persistence, I estimated population size in the three Montgomery County, Maryland, parks using mark-recapture techniques, and compared these estimates to the number of dead, injured, and live turtles in or very near roads observed during walking and driving surveys conducted in 2006. Road-based morality rates fell within the range estimated to be inconsistent with population growth in one of the parks. Road mortality appeared to affect females out of proportion to their abundance in the population. Suggestions for reducing box turtle mortality in areas associated with high mortality rates are included.Item THE MITOCHONDRIAL GENOME OF THE BLUE CRAB (CALLINECTES SAPIDUS), AN INFORMATIVE GENETIC MARKER FOR THE EVOLUTIONARY BIOLOGY AND POPULATION GENETICS OF THE SPECIES(2009) Feng, Xiaojun; Place, Allen R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The blue crab (Callinectes sapidus) is a widely distributed decapod which ranges from Nova Scotia to the northern Argentina coasts. It is one of the most abundant estuarine invertebrates, supporting both commercial and recreational fisheries along the Atlantic and Gulf coasts. This thesis presents data clearly establishing the unprecedented hyper-variability in the mitochondrial genome of C. sapidus. This variation extended to multiple regions, including the cox1, nad2, and nad4 protein coding loci as well as ribosomal 12s RNA molecule. The haplotype diversity of the nad2 gene approached 1, with a nucleotide diversity approaching 1%. This hyper-variability in the mtDNA allows using a single mtDNA gene (nad2) to distinguish hatchery-produced crabs from wild crabs after release to the wild. I found no dominant mtDNA haplotypes in wild populations but instead a distribution of a few low-frequency recurrent haplotypes with a large number of singletons. Because of this high diversity and extensive population mixing, the geographic structure in wild populations exhibits panmixia from the Atlantic to Gulf of Mexico. Some of the high genetic diversity found seems to stem from the heteroplasmic nature of the blue crab mtDNA. By cloning high fidelity PCR products, I confirmed single individual crab and megalopa harbored dozens of copies of mitochondrial haplotypes. A copy number analysis indicates discovery of unique haplotypes was probably not saturated with the possibility of inadequate sampling. The heteroplasmy in the blue crab appears to be under maternal inheritance without paternal contribution. While minor haplotypes are represented in wild populations, other minor haplotypes contained stop codons and/or non-synonymous substitutions which may influence the viability of the mitochondria. Given the blue crab inhabits a broad variety of environments and that the mtDNA genome appears to be under selective pressure, the potential for mtDNA functional correlates with this genetic diversity maybe at the basis for the robust physiological capability of the species.Item Genetic Determinant of Silicibacter sp. TM1040 Motility(2008-12-04) Suvanasuthi, Rooge; Belas, Robert; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Silicibacter sp. TM1040 is a member of the Roseobacter clade. Roseobacters play an important role in sulfur cycling in the ocean by degrading dimethylsulfoniopropionate (DMSP). Roseobacters are found in communities associated with most marine habits, especially with marine algae. Therefore, the ability to sense, move towards and maintain the interaction is an important physiological trait for the symbiosis between roseobacters and dinoflagellate. Previous work from our laboratory demonstrated that TM1040 is chemotaxis towards DMSP and DMSP catabolites, and motility of TM1040 is important for growth of P. piscicida. In contrast to enteric bacteria, little is known about the genes regulating motility in roseobacter species. This study, revealed similarities between the genes associated with motility in TM1040 and those from other α-proteobacteria species, but most importantly, it identified three new regulators that maybe involved in regulating the motility of TM1040.Item Expression of recombinant proteins in the methane-producing archaeon Methanosarcina acetivorans(2005-12-16) MacAuley, Sheridan Rose; Sowers, Kevin R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recombinant protein expression is a necessary tool for the investigation of proteins in the post-genomic era. While many systems exist for recombinant protein expression in organisms of the eukaryotic and eubacterial domains, few to none are available in the Archaea. A recombinant protein expression system using the methanogenic archaeon Methanosarcina acetivorans was developed which uses the highly regulated cdh promoter and allows expression of recombinant protein with optional 6xHis protein fusions to facilitate rapid purification. A protocol for high-density mass cultivation of M. acetivorans in a stainless steel bioreactor configured as a pH-auxostat was developed. The cdh promoter and alternate promoters were analyzed in attempt to enhance expression of recombinant proteins. The protein expression system was tested on several proteins: the Methanocaldococcus jannaschii prolyl tRNA synthetase, the M. acetivorans prolyl tRNA synthetase, the Methanosarcina thermophila carbonic anhydrase, and the Dehalococcoides ethenogenes tricholorethylene dehalogenase.