In this thesis, I try to proceed one step further towards an understanding of the biogeographic processes forming the distribution patterns of organisms that we see today. Babblers and warblers are diverse groups of passerines that are phylogenetically intermixed with other groups in the superfamily Sylvioidea. First, the gross phylogeny of the babblers and associated groups was estimated. Five major lineages of a well-supported monophyletic babbler radiation were recovered, and we proposed a new classification at family and subfamily level. Further, the genus Pnoepyga was excluded from Timaliidae, and we proposed the new family Pnoepygidae fam. nov. Second, the systematic position was investigated for the Albertine Rift taxon Hemitesia neumanni, which was found to be nested within the almost entirely Asian family Cettidae, and possible biogeographical scenarios were discussed. We concluded that the most plausible explanation involved late Miocene vicariance in combination with local extinctions. Third, the historical biogeography of a Leiothrichinae subclade, the Turdoides babblers and allies, was inferred. We concluded that the Middle East region probably played an important role in the early history of this clade, followed by local extinctions in this region. Fourth, a Bayesian method to reconstruct the historical biogeography under an event-based model was proposed, where the total biogeographic histories are sampled from its posterior probability distribution using Markov chains. In conclusion, I believe that, especially with more sophisticated methods available, we will see an increasing number of studies inferring biogeographic histories that lead to distribution patterns built up by a combination of dispersals and vicariance, but where these distributions have been extensively reshaped, or litterally demolished, by local extinctions. Therefore, my answer to the frequently asked question dispersal or vicariance? is both, but not the least: extinctions. / At the time of the doctoral defence the following papers were unpublished and had a status as follows; Papers 3 and 4: Manuscripts

No description available.

Abstract Dissimilatory microbial sulfate reduction (MSR) The specific objectives of the study were to provide the first measurements of sulfur isotope fractionation associated with acidophilic sulfate reducing-microorganisms, and to examine whether pH influences sulfur fractionation during MSR. The fractionation associated with the strains investigated was comparable to that of neutrophilic strains with similar metabolisms (4-12‰), but varied with pH. Two fractionation regimes were identified: one regime is consistent with fractionation during exponential growth, while the other – not identified previously - is not linked to active sulfate reduction and may result from internal sulfate accumulation. This would represent the first measurement of sulfur fractionation during sulfate uptake, the first step of MSR. Geological processes at the Cretaceous-Paleogene (KPg) boundary The KPg boundary is associated with one of the largest biological extinctions in the history of our planet. Two major geologic events - the Chicxulub bolide impact with evaporite terrane and the eruption of the Deccan continental flood basalts - coincide with the KPg boundary and have been identified as possible triggers for the extinctions, but their relative timing remains unresolved. The objectives of this study were to identify the contribution of these processes to the sulfur burden in the sedimentary environment of two freshwater KPg sections, and to determine their relative timing. The results demonstrate that the peak of Deccan volcanism post-dates the Chicxulub impact and the associated abrupt KPg mass extinction, thus precluding a direct volcanic causal mechanism, but shedding light on the underlying causes for the delayed recovery of ecosystems in the early Paleogene.

Photocopy of typescript. / Bibliography: leaves 58-62. / Microfiche. / vii, 62 leaves ill. 29 cm

Several late Pleistocene fossil localities in the Kings Creek catchment, Darling Downs, southeastern Queensland, Australia, were examined in detail to establish an accurate, dated palaeoecological record for the region, and to test human versus climate change megafauna extinction hypotheses. Accelerator Mass Spectrometry (AMS 14C) and U/Th dating confirm that the deposits are late Pleistocene in age, but the dates obtained from the two methods are not in agreement. Fluvial depositional accumulation processes in the catchment reflect both high-energy channel and low-energy episodic overbank deposition. The most striking taphonomic observations for vertebrates in the deposits include: 1) low representation of post-cranial elements; 2) high degree of bone breakage; 3) variable abrasion but most identifiable bone elements with low to moderate degree of abrasion; 4) low rates of bone weathering; 5) low degree of carnivore bone modification; and 6) low degree of articulated or associated specimens. Collectively, those data suggest that the material was transported into the deposit from the surrounding proximal floodplain and that the assemblages reflect hydraulic sorting. A multifaceted palaeoecological investigation revealed significant habitat change between superposed assemblages of site QML796. The basal fossiliferous unit contained species that indicate the presence of a mosaic of habitats including riparian vegetation, vine thickets, scrubland, open and closed woodlands, and open grasslands during the late Pleistocene. Those woody and scrubby habitats contracted over the period of deposition so that by the time of deposition of the youngest horizon, the creek sampled a more open type environment. Sequential faunal horizons show a step-wise decrease in taxonomic diversity that cannot be explained by sampling or taphonomic bias. The decreasing diversity includes loss of some, but not all, megafauna and is consistent with a progressive local loss of megafauna in the catchment over an extended interval of time. Collectively, those data are consistent with a climatic cause of megafauna extinction, and no specific evidence was found to support human involvement in the local extinctions. Better dating of the deposits is critically important, as a secure chronology would have significant implications regarding the continent-wide extinction of the Australian megafauna.

A global extinction event has been documented in protozoan foraminifera in the late Pliocene to Pleistocene. The timing of the extinction event varied depending on location, however for Ocean Drilling Project Site 1125, disappearances occurred between 2.5 and 0.57 Ma, with the major decline approximately 1.1 Ma. In order to determine if this event affected benthic organisms other than protozoans, this study was undertaken to determine how podocopid ostracods (Crustacea) recovered Ocean Drilling Program Site 1125 responded. The present study was hindered by the small number of valves recovered; the fact that a large proportion of taxa found were undescribed and new to science; and the current state of taxonomic scheme that is under significant revision. These factors meant that a comprehensive comparison could not be achieved. Despite this, counts of ostracod valves and assessments of diversity from this study reveal a significant increase in both parameters from approximately 900-600 ka. Three possible causes were investigated to account for this increase, sediment type and sample size; affects of taphonomy, mainly dissolution; or an actual biotic 'event'. Statistical analyses showed that although sample size did have some effect, it was not the sole reason for the increase in ostracod numbers. Dissolution had an expected affect on the percentage of juveniles but no correlations were found with other sample characteristics. Sedimentation rate was investigated but this also proved unrelated. Therefore, it is suggested that the increase in total ostracod valves and diversity which occurs between 900 and 600 ka was in fact a natural, biotic 'event'. This preliminary evidence suggests that an oceanographic event that has negatively impacted on the foraminifers has had the reverse affect on the ostracod assemblage, in the sense that both population size and diversity increase during that time.

The ventral tegmental area (VTA) and its dopaminergic (DA) mesocorticolimbic projections are thought to be essential in the brain’s reward neurocircuitry. In humans and animal experimental subjects, mild electrical VTA stimulation increases dopamine levels and can induce euphoria. Paradoxically, aversive stimuli activate VTA neurons and forebrain DA activity, and excessive electrical stimulation of the VTA exaggerates fearfulness. Research suggests that experimental manipulation of either the amygdala or the VTA has similar effects on the acquisition and expression of Pavlovian conditioned fear. Recently it was demonstrated that electrical stimulation of the amygdala produced fear extinction deficits in rats. Fear extinction involves the progressive dissipation of conditioned fear responses by repeated non-reinforced exposure to a conditioned stimulus (CS). Maladaptive states of fear in fear-related anxiety disorders, such as post-traumatic stress disorders (PTSD) or specific phobias are thought to reflect fear extinction learning deficits. The primary purpose of the present study was to examine the effects of intra-VTA stimulation on fear extinction learning. Using fear-potentiated startle as a behavioural index of conditioned fear, it was found that 120 VTA stimulations paired or unpaired with non-reinforced CS presentations impaired the extinction of conditioned fear. This effect was not apparent in rats that received electrical stimulation of the substantia nigra (SN), suggesting that not all midbrain regions respond similarly. Electrical stimulation parameters did not have aversive affects because rats failed to show fear conditioning when electrical VTA stimulation was used as the unconditioned stimulus. Also, VTA stimulation did not alter conditioned fear expression in non-extinguished animals. Based on the results it is suggested that VTA activation disinhibited conditioned fear responding. Therefore, VTA neuronal excitation by aversive stimuli may play a role in fear-related anxiety disorders thought to reflect extinction learning deficits.

Thesis (Ph. D.)--Cornell University, 2008. / Title from PDF t.p. (viewed on Apr. 20, 2009). Vita. Includes bibliographical references. Mode of access: World Wide Web.

Thesis (Ph. D.)--Worcester Polytechnic Institute. / Keywords: suppression; drop size; high flash point pool fire. Includes bibliographical references (p. 210-218).

Thesis (M.S.)--State University of New York at Binghamton, Department of Psychology, 2009. / Includes bibliographical references.