Browsing by Author "Bickham, John W."
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Item A comparison of diversity in the zfy gene in two species of pinnipeds with different breeding strategies(Texas A&M University, 2006-04-12) Sweny, Jason MichaelSequence variation was examined for the Zinc-finger Y (zfy) gene and the mitochondrial control region for two species of pinnipeds, the Steller sea lion (Eumetopias jubatus) and harbor seal (Phoca vitulina). The two species differ in aspects of their breeding strategies, dispersal, and life histories. Comparable stock sample sizes of males from each species were taken from localities that span at least one wellrecognized phylogeographic stock as defined by mtDNA markers. Variation in zfy, a strictly paternally inherited marker located on the Y chromosome, was low in both species. An interesting pattern of subdivision was found for zfy in harbor seals that was concordant with population subdivision for mtDNA. In Steller sea lions, no such concordant pattern was evident with only a single rare zfy variant being observed. One explanation for the different patterns observed is that dispersal is less in male harbor seals than in male Steller sea lions.Item Cave and cliff swallows as indicators of exposure and effects of environmental contaminants on birds from the Rio Grande, Texas(Texas A&M University, 2004-11-15) Musquiz, DanielCave (Petrochelidon fulva) and cliff swallows (Petrochelidon pyrrhonota) were collected along the Rio Grande and evaluated as potential indicators of environmental contamination. The Rio Grande receives toxic substances from agricultural, industrial, municipal, and non-point sources; consequently, high levels of contaminants have been detected in birds, mammals, fishes and sediments. Swallows were obtained from 8 sites between Brownsville and El Paso, as well as from a reference site in Burleson County, 320 miles north of the nearest site of the Rio Grande. Blood samples were analyzed by flow cytometry, a technique that allows the detection of DNA damage in blood and other tissues. Plasma samples were analyzed for thyroid hormones using a radioimmunoassay technique. Organochlorines and trace metal analysis was limited to a few samples. DDE and PCB levels were below levels known to cause reduced hatching, embryo mortality, and deformities, Hg, Pb, and As were below detection, and Se, Ni and Cr concentrations were lower than levels known to cause harm in birds. Neither species showed sex-related differences in chromosome damage. Cave swallows from the Del Rio area had the highest levels of DNA variation, which may be indicative of DNA damage, possibly from PAHs exposure. Previous studies indicate that sediment samples from tributaries near Del Rio have high levels of chromium compared to other sites along the Rio Grande. A significant increase in DNA variation between sampling years was detected in cave swallows from Llano Grande Lake. Wildlife samples collected from Llano Grande Lake have recorded high levels of DDE and PCBs; in addition, this urban/agricultural contaminant sink appears to be affected by PAH exposure. T3 levels were below the detection limit of the radioimmunoassay. There were no gender related differences in T4 levels in cave swallows. Cave swallows sampled from Laredo had significantly higher T4 levels than those from birds at other sites during 1999. It was not possible to determine thyroid hormone disruption in plasma samples. Thyroid hormone and flow cytometry data were useful in establishing baseline data. Areas of concern based on genotoxic data include Llano Grande Lake, Del Rio, and El Paso.Item Combining environmental chemistry, somatic biomarkers, and population genetics: an innovative approach in wildlife ecotoxicology(Texas A&M University, 2004-09-30) Matson, Cole WesleyThe Caspian region and specifically the Apsheron peninsula of Azerbaijan is known to be polluted with a variety of environmental contaminants, making risk assessment difficult. The wetlands of Sumgayit contain particularly complex mixtures of contaminants. Flow cytometry and the micronucleus assay were used to assess chromosomal damage in aquatic turtles and frogs inhabiting contaminated wetlands in Azerbaijan. By evaluating biomarkers that are indicative of somatic effects, elevated chromosomal damage was documented at several sites in Azerbaijan relative to reference sites. Sediment samples were analyzed for polycyclic aromatic hydrocarbons (PAHs), organochlorines (OCs), and mercury to evaluate contaminant associations with genetic damage. Sediment samples revealed heterogeneous patterns of PAH and mercury concentrations throughout Sumgayit. Significant positive correlations were documented between both PAH and mercury sediment concentrations and chromosomal damage. Population genetic methods were employed to study the effects of long-term chronic contaminant exposure in marsh frogs from Sumgayit. The Sumgayit region has reduced levels of genetic diversity, likely due to environmental degradation. One of the most contaminated sites in Sumgayit, WTP, appears to be a source of new mutations as a result of an increased mutation rate. Finally, the Sumgayit region seems to act as an ecological sink, with levels of gene flow into the region exceeding gene flow out of the region. This study provides not only exposure and biomarker data, but also an integrated method for assessing the cumulative population impacts of contaminant exposure by studying both population genetic and evolutionary effects. The results presented here will be used in conjunction with those of ongoing research involving both wildlife and humans to develop comprehensive ecological and human risk assessments.Item Did bowhead whales (Balaena mysticetus) from the Bering-Chukchi-Beaufort Seas undergo a genetic bottleneck? A test using nuclear microsatellite loci(Texas A&M University, 2005-11-01) Hunter, Devra DeniseThis study reexamines the nuclear microsatellite analysis by Rooney et al. (1999a) of Bering-Chukchi-Beaufort Seas bowhead whales (Balaena mysticetus) to determine if this population underwent a genetic bottleneck as a result of 19th and early 20th Century commercial whaling. This investigation used more accurate laboratory techniques to score alleles, had a larger sample size that was divided into two groups (mainland Alaska and St. Lawrence Island (SLI)), and used a moderately different set of microsatellite loci which are more variable and thus, more informative. The results corroborate the findings of Rooney et al. (1999a) for mainland Alaska showing no evidence of a genetic bottleneck. However, the SLI data analyses provide conflicting conclusions. The Wilcoxon test is significant for a heterozygote excess (p = 0.042) suggesting that a genetic bottleneck has occurred. This is not substantiated by the exact tests of each locus or the table-wide sign test. There is a possibility that a bottleneck has occurred, but due to the small sample size this is not a definitive conclusion and warrants reanalysis with a larger sample size.Item Genetic relationships and evolutionary history of extant Bowhead whale populations, Balaena mysticetus(2009-05-15) Huebinger, Ryan MichaelBowhead whales, Balaena mysticetus, are large baleen whales that are characterized by an Arctic distribution. In order to provide proper management recommendations to the International Whaling Commission, a panel of twenty-five microsatellite markers was developed. This panel consisted of pure cytosine-adenine (CA) repeats and was selected for their ability to consistently amplify and for their consistency for allele designations. This panel was utilized to investigate stock structure within the Bering-Chukchi-Beaufort population of bowheads. Over thirty reports and manuscripts utilized these data for providing management recommendations to the International Whaling Commision. From this work it was concluded that there is presently one stock of bowhead whales within the Bering-Chukchi-Beaufort seas. This data was also utilized to examine the genetic relationships of the remaining extant bowhead populations. The microsatellite data, in combination with sequences from the mitochondrial control region and the NADH dehydrogenase subunit 1 (ND1) region, were used to examine population structure. The Okhotsk Sea was identified as the most divergent population of bowheads. Relationships among the extant populations demonstrated high levels of effective gene flow between populations. Gene flow appeared to be female-biased in relation to the Okhotsk Sea, whereas gene flow between Canada and the Bering-Chukchi-Beaufort populations appears to be equal between the bowhead whale sexes.Item Phylogenetics of the genus Scotophilus (Chiroptera: Vespertilionidae): perspectives from paternally and maternally inherited genomes with emphasis on African species(Texas A&M University, 2006-10-30) Trujillo, Robert GregBats of the genus Scotophilus are distributed throughout sub-Saharan Africa, parts of southern and Southeast Asia, a majority of the Indomalayan Islands, Reunion Island, and Madagascar. The genus is composed of 14 recognized species with seven distributed throughout sub-Saharan Africa including: (S. dinganii (A. Smith, 1833), S. leucogaster (Cretzschmar, 1830), S. nigritellus de Winton, 1899, S. nigrita (Schreber, 1774), S. nucella Robbins, 1983, S. nux Thomas, 1904, and S. viridis (Peters, 1852). The remaining species include four from southern and southeast Asia (S. celebensis Sody, 1928; S. collinus Sody 1936; S. heathi (Horsfield, 1831); S. kuhlii Leach, 1821), two on Madagascar (S. sp. nov. Goodman et al., in press; and S. robustus Milne-Edwards, 1881), and one endemic to Reunion Island (S. borbonicus (E. Geoffroy, 1803). The systematics and taxonomy of this genus have been controversial and continue to be confusing. The genus is plagued with problems in species definition and the systematic relationships among members of the genus are poorly understood. The major goal of this study was to use a molecular phylogenetic approach to clarify some of the controversy and confusion surrounding the members of this genus. Nucleotide differences from mtDNA and the Y chromosome were used to examine phylogenetic patterns within Scotophilus. Based on these data two new species of Scotophilus were identified. Phylogenetically, African Scotophilus were found to comprise a monophyletic group with S. nux as the most basal African taxon. Overall, the Asian S. kuhlii was the most basal taxon. A distant relationship was identified between S. kuhlii and S. heathi, the other Asian species examined. The multiple origins of Malagasy Scotophilus are apparent as the two Malagasy taxa in the study do not share a sister-group relationship. The large bodied S. nigrita is closely related to S. dinganii and the S. dinganii-like species all share a close relationship. S. nigrita has a S. dinganii-like mtDNA haplotype and a very distinct zfy haplotype, suggesting a possible hybridization event with a S. dinganii-like ancestor.Item Variation of mitochondrial control region sequences of Steller sea lions: the three-stock hypothesis(Texas A&M University, 2004-09-30) Baker, Alyson ReneeSequence variation of a 238 bp segment of the mitochondrial control region was analyzed for 1,568 Steller sea lions (2.8% of the estimated species population) sampled from 50 rookeries representing nearly every locality at which Steller sea lions are known to breed in significant numbers. Haplotype diversity (H = 0.9164 ? 0.0035) was high and nucleotide diversity (? = 0.00967 ? 0.00586) was moderate. No evidence was observed for significant genetic bottleneck effects. Rookeries were grouped into regions and stocks to examine structure at different spatial scales. F- and ?-statistics were computed for all pairwise comparisons of rookeries, regions and stocks. Significant (P<0.05) divergence of eastern stock (southeastern Alaska to California) animals from western stock animals was supported in analyses at all spatial scales. Likewise, rookeries and regions from Asia were found to be significantly different from all other western stock rookeries. This was most clearly demonstrated using ?-statistics at the regional level. The Commander Islands clearly associate with Alaskan western stock rookeries, not with the Asian rookeries. Within each of the three stocks there is significant isolation by distance among rookeries. This relationship does not hold for inter-stock comparisons indicating that there are important barriers to gene flow among stocks. Mitochondrial DNA analysis supports the recognition of three stocks for appropriate conservation of the species. The currently recognized eastern stock is unaffected, but the western stock is now partitioned west of the Commander Islands yielding a western stock which ranges from Prince William Sound west to the Commander Islands, and an Asian stock including rookeries from the Kamchatka Peninsula, Kuril Islands, and Sea of Okhtosk.