Browsing by Subject "paleoecology"
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Item Mid-Cretaceous Palynoflora from Central Mid-Pacific Ocean(2012-10-19) Hsiung, Shih-YiAlbian (late Early Cretaceous) pollen and spores were used to reconstruct the floral history of Allison Guyot in the Albian period, to better understand pollen and spore distributions on mid-oceanic islands, to investigate whether Allison Guyot supported land plants in the Albian, and to test previous hypotheses about the development of the guyot. Albian spores found in Allison Guyot sediments from ODP Leg 143 Site 865 include: Laevigatosporites ovatus, Cyathidites minor, Cicatricosisporites sp., Baculatisporites comaumensis, Ceratosporites equalis, Gleicheniidites senonicus, Leptolepidites verrucatus, Retitriletes circolumenus, Lycopodiacidites dettmannae, Osmundacidites wellmanii, Cicatricosisporites hughesii, Impardecispora excavate, and others. Albian pollen from these samples include Callialasporites dampieri, Ephedra, and others occur in Albian samples. The high abundance of terrestrial palynomorphs in these samples suggests that Allison Guyot was exposed in the Albian and supported land plants. The high frequency of spores (more than 90 percent) reflects a flora dominated by ferns.Item Revisiting Copano Bay, Texas: an exceptional long-term record of ecological communities and their associated death assemblages(Texas A&M University, 2006-10-30) Ebnother, Danielle DawnThanks to previous work conducted by Staff et al. (1986), Copano Bay on the Texas coast presents an exceptional research area for studying 1) the effect of living volatility on death assemblage diversity and composition and 2) the stability of death assemblage diversity. Staff et al. (1986) revisited one site in Copano Bay every six weeks for 18 months in 1981-1982. In order to test the variability of both the live and dead assemblages of Copano Bay, Texas, the transect originally established by Staff et al. (1981) in 1981-1983, was reestablished in 2004 and sampled every six weeks for a duration of one year. Taxonomic abundance, diversity, and composition of these assemblages were compared to each other and those of Staff et al. (1981) in order to understand how both the living and dead assemblages have changed in the intervening 22 years. Important findings include: 1. Death assemblage composition in Copano Bay changed over 22 years more than expected based on short-term variation; 2. The death assemblages in Copano Bay reflected changes in taxonomic composition of the corresponding living community; 3. The death assemblages of Copano Bay were found to predominantly reflect the local, rather than the entire regional, species pool; and 4. Variation in diversity occurred at both six-week and 22-year time scales, indicating that the death assemblages at the study site are variable. Understanding time averaging and its effects on death assemblages will not only aid in paleocommunity reconstruction, but also aid in the construction of modern ecologic baselines.Item Utilizing Vertebrates to Understand the Factors that Influence Terrestrial Ecosystem Structure(2012-07-16) Redman, CoryConserving biodiversity in the current global ecological crisis requires a robust understanding of a multitude of abiotic and biotic processes operating at spatial and temporal scales that are nearly impossible to study on a human timescale and are therefore poorly understood. However, fossil data preserve a vast archive of information on past ecosystems and how they have changed through time. My PhD research is composed of three studies that look at biogeogaphic distribution, ecosystem structure, and trends in richness and diversity. Identifying organisms to the species level is a common practice in ecology when conducting community analyses. However, when species-level identification is not feasible, higher level taxonomic identifications are used as surrogates. This study tests the validity of supraspecific identifications for vertebrates in regional biogeography studies, using the recorded occurrences of terrestrial and aquatic taxa from 16 national parks on the Colorado Plateau and culling the data set based on a series of taphonomic processes to generated fossil assemblages. Changes in community structure as a result of increased magnitude and/or frequency of perturbations have been well documented in terrestrial and marine ecosystems. Unfortunately, the long-term effects of sea-level rise on vertebrate communities in coastal habitats are poorly understood and difficult to study on a human time scale. This study examines the long term effects of relative sea-level change on coastal plain ecosystems of the Belly River Group (Campanian) in southern Alberta using microvertebrate fossils. Most Cretaceous freshwater deposits in North America produce only a couple of articulated fish skeletons. Because of this preservational bias many workers suggested that freshwater teleosts were largely absent from North America until the Eocene or later. Late Cretaceous fish assemblages are of particular interest, because these assemblages undergo a major compositional change. Pre-Cretaceous fish assemblages are dominated by non-teleosts, while Paleogene assemblages are dominated by teleosts that are members of extant families. This study provides a first approach in characterizing long-term trends in richness and the distribution of Late Cretaceous, nonmarine actinopterygians of the Western Interior of North America.