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Effects Of Riverine Barriers On Avian Evolution In The Amazon Basin, Andre Eugene Moncrieff
Effects Of Riverine Barriers On Avian Evolution In The Amazon Basin, Andre Eugene Moncrieff
LSU Doctoral Dissertations
The high biodiversity found in the Amazon Basin has long captivated the attention of naturalists and evolutionary biologists seeking to explain its origins. Early observations by Alfred Wallace highlighted the role of rivers in delimiting the geographic ranges of many species; furthermore, where rivers narrow towards their headwaters, he noted that some species cross rivers freely. A major goal of this dissertation is to investigate how these and other observations about riverine barriers might inform our understanding of how speciation unfolds in Amazonia. My approach involved generating genomic data with dense geographic sampling for manakins in the genus Lepidothrix, …
Evolution Of Freshwater Fishes In The Northern Neotropics, Diego Elias
Evolution Of Freshwater Fishes In The Northern Neotropics, Diego Elias
LSU Doctoral Dissertations
The northern Neotropics (NN) represents one of the most geologically-complex regions on the planet, composed of island-like geological blocks that have undergone multiple episodes of isolation and connectivity at various geological times. The riverscapes of the NN harbor a unique assemblage of freshwater fishes. In contrast to the freshwaters systems of South America, which are dominated by ostariophysan lineages, the aquatic systems of the NN are dominated by lineages of two families: Cichlidae (cichlids) and Poeciliidae (livebearers). It has been suggested that the geologically complex nature of the region allowed ancestors of cichlids and livebearers to colonize and radiate within …
The Modern Mississippi: Provenance Indicators And Human Impact, Brittney Anne Gregory
The Modern Mississippi: Provenance Indicators And Human Impact, Brittney Anne Gregory
LSU Doctoral Dissertations
Given the significant degree to which the modern Mississippi River and its tributaries have been altered through dams, levees, and diversions, it is important to understand how sediment is transported from source to sink. The objective of this dissertation is to explore how the modern Mississippi River transports sediment from its tributaries to its delta using three independent proxies. Provenance indicators have traditionally been an effective way with which to characterize sediment transport in large river systems. First, detrital U-Pb zircon dating is used to investigate modern flux and possible anthropogenic influences on coarse-grained sediment within the modern Mississippi River. …
Untangling Earth System Responses Recorded In Sulfate's Sulfur And Oxygen Isotopes At The Dawn Of Multicellular Life And Today, Bryan Alan Killingsworth
Untangling Earth System Responses Recorded In Sulfate's Sulfur And Oxygen Isotopes At The Dawn Of Multicellular Life And Today, Bryan Alan Killingsworth
LSU Doctoral Dissertations
Major Earth system perturbations in the deep past and today are recorded in sulfate sulfur and oxygen isotopes, as examined here in three cases. (1) Sedimentary sulfate record of the “Marinoan Oxygen-17 Depletion” (MOSD) event, implies ultra-high CO2 atmosphere at ~635 Ma after global glaciation. MOSD duration is constrained by correlating its most complete record to radiometric dates. Barium sulfate layers in South China sediments show the MOSD in lower layers but persistently absent up section. Carbon-13 correlation locates the MOSD within dated intervals from other sites, yielding a 0 - 0.99 Myr duration. Thus, sedimentary constraint on this non-steady-state …