This study surveys late Holocene vertebrate fossils from Isla Floreana, Galapagos Islands. 20,000 fossils from four lava tubes near Post Office Bay are loosely associated with four radiocarbon dates of 2400 years BP or younger. Most fossils originated as regurgitated pellets of barn owls (Tyto punctatissima). They include six species now extinct on Floreana: Geochelone elephantopus, Alsophis biserialis, Tyto puntatissima, Mimus trifasciatus, Geospiza nebulosa, and Geospiza magnirostris. These species are, respectively, 1st, 7th, 16th, 6th, 15th, and 2nd in abundance among those recorded as fossils, making up 57% of individuals in the fauna. Thus extinction probably has changed the composition of Floreana's fauna even more than suggested by the number of extinct species alone. The evidence is circumstantial, but I believe that all extinction on Floreana is related to human impact, such as predation, habitat alteration, and introduction of alien animals (rats, mice, cats, dogs, pigs, goats, cattle, and donkeys). Direct human predation was probably the main cause of extinction only for Geochelone elephantopus. Extinction of Tyto punctatissima was probably due to loss of preferred prey species. Extinction of Mimus trifasciatus and Geospiza magnirostris may have accompanied destruction of Opuntia cactus. Extinction of Geospiza nebulosa may be related to habitat changes in the highlands. All extinction on Floreana probably occurred in historic times; whether this is true elsewhere in the Galapagos awaits more research. The lack of fossils of Coccyzus melacoryphus and Dendroica pectechia is further evidence that these birds colonized the Galapagos very recently. Fossils enable us to reconstruct natural, pre-human faunas more completely than previously possible. Modern biogeographical studies usually do not consider how natural the faunas are; they would benefit by considering changes wrought by human impact.

Oceanic island volcanoes such as those in the Hawaiian, Canary and Galapagos Islands are known to become unstable, causing failures of the subaerial and submarine slopes of the volcanic edifices. These mass wasting events appear to be the primary source of destruction and loss of volume of many oceanic islands, but our knowledge of mass wasting is still rudimentary in many seamount and island chains. To better understand mass wasting in the western Galapagos Islands, multi-beam bathymetry and backscatter sidescan sonar images were used to examine topography and acoustic backscatter signatures that are characteristic of mass wasting. Observations show that mass wasting plays an important role in the development of Galapagos volcanoes. While volcanic activity continues to conceal the submarine terrain, the data show that four forms of mass wasting are identified including debris flows, slumps sheets, chaotic slumps, and detached blocks. A total of 23 mass wasting features were found to exist in the western Galapagos Islands, including fourteen debris flows with one that incorporated a set of detached blocks, seven slump sheets, and one chaotic slump. Some of the indentified features have obvious origination zones while the sources of others are not clearly identifiable. Approximately 73 percent of the surveyed coastlines are affected by slumping on the steep upper slopes and ~64 percent are affected by debris flows on the lower slopes. Unlike the giant landslides documented by GLORIA imagery around the Hawaiian Islands, the western Galapagos Islands appear to be characterized by small slump sheets existing along the steep shallow submarine flanks of the island and by debris flows that are flanked by rift zones and extend off the platform. This study indicates that submarine mass wasting is widespread in the western Galapagos, suggesting that the production of small-scale downslope movement is part of the erosive nature of these oceanic volcanic islands.

No description available.

Sediment sampling, bathymetric data, and seismic reflection profiling were used to classify sediment deposition patterns on the Carnegie Ridge. Core sampling was used to relate compositional characteristics between equivalent areas, and seismic profiling to establish vertical variations. Three study areas were selected based on core distribution along the ridge. Grids of the following parameters were obtained: slope, elevation, percentage of carbonate, SiO2, and organic carbon contents. The general CaCO3 content distribution is highest on the ridge except in the areas affected by terrigenous deposition from the mainland, and volcanic debris from Galapagos Volcanic Platform. The general SiO2 content distribution is highest south of the Equator, bordering the west ridge. The organic carbon content is high in the equatorial upwelling area and close to the mainland. The relationship between organic carbon and carbonate was determined through correlation analysis. Based on those analyses, and considering the mixture of sedimentary sources and tectonic processes, the carbonate sediment is more important to this area. Sediments on the Carnegie Ridge above the lysocline are affected by three different types of processes controlling the sediment deposition. The first is the location of the high productivity zone in which pelagic settling is the source of sediment. The second is the difference in sea water properties between the Panama and Peru Basins surrounding the ridge, which creates different depositional environments. These properties create horizontal and vertical variations within water masses. Intermediate depths are affected by northward Pacific Central Water and bottom waters by northward Pacific Deep Water. The deflection of the bottom water flow by the existence of the Carnegie Ridge as a natural barrier produces scouring effects on the south flank. The third process controlling deposition is underwater dissolution on the saddle and east ridge by organic carbon degradation, which is enhanced by bottom water flow. Significant differences in sedimentation types were found in areas with hilltops, contrasted slopes, and slope bases, primarily related to changing depths and water flows, and lateral transport along the steepest north scarp.

Sediment sampling, bathymetric data, and seismic reflection profiling were used to classify sediment deposition patterns on the Carnegie Ridge. Core sampling was used to relate compositional characteristics between equivalent areas, and seismic profiling to establish vertical variations. Three study areas were selected based on core distribution along the ridge. Grids of the following parameters were obtained: slope, elevation, percentage of carbonate, SiO2, and organic carbon contents. The general CaCO3 content distribution is highest on the ridge except in the areas affected by terrigenous deposition from the mainland, and volcanic debris from Galapagos Volcanic Platform. The general SiO2 content distribution is highest south of the Equator, bordering the west ridge. The organic carbon content is high in the equatorial upwelling area and close to the mainland. The relationship between organic carbon and carbonate was determined through correlation analysis. Based on those analyses, and considering the mixture of sedimentary sources and tectonic processes, the carbonate sediment is more important to this area. Sediments on the Carnegie Ridge above the lysocline are affected by three different types of processes controlling the sediment deposition. The first is the location of the high productivity zone in which pelagic settling is the source of sediment. The second is the difference in sea water properties between the Panama and Peru Basins surrounding the ridge, which creates different depositional environments. These properties create horizontal and vertical variations within water masses. Intermediate depths are affected by northward Pacific Central Water and bottom waters by northward Pacific Deep Water. The deflection of the bottom water flow by the existence of the Carnegie Ridge as a natural barrier produces scouring effects on the south flank. The third process controlling deposition is underwater dissolution on the saddle and east ridge by organic carbon degradation, which is enhanced by bottom water flow. Significant differences in sedimentation types were found in areas with hilltops, contrasted slopes, and slope bases, primarily related to changing depths and water flows, and lateral transport along the steepest north scarp.

A three year study on Daphne Major island, Galapagos, describes the ecology and morphology of a simple Geospiza community. The four part thesis discusses the breeding and feeding ecology of two Daphne finches; G. fortis is a generalist adapted to a variable environment, and G. scandens is an ecological specialist experiencing a more stable environment. The measurement, growth, allometry, and multivariate properties of seven external morphological characters are described. The repeatabilities and heritabilities of the seven characters and principal component scores are large. Relations between the unusual intermediate-sized Daphne G. fortis phenotype and the Daphne environment are examined. Four hypotheses for the intermediacy, including genetic drift, hybridization, local adaptation, and competition are suggested, with evidence found to support parts of each except genetic drift. An episode of intense directional natural selection is documented, and Lack's character release explanation of the Daphne G. fortis phenotype is revised.

No description available.

Large-scale climate modes such as the El Niño/Southern Oscillation (ENSO), the Asian monsoon, and the Arctic Oscillation are responsible for much of the Earth’s climate variability. Despite the importance of these modes, we have limited understanding of how they vary on long (multidecadal to millennial) timescales due to the short length of instrumental climate records. Fortunately, climate information stored in natural archives can provide us with information on how these modes varied in the more distant past. Lake sediments are an ideal climate archive since they are continuous, have high temporal resolution, and contain many potential climate proxies. In the present study, I use lake sediment records to assess past climate and environmental changes associated with the El Niño/Southern Oscillation, the Asian monsoon, and the Arctic Oscillation. Exploring modern precipitation variability across the Asian monsoon region, I found that precipitation within this broad area is not coherent, which holds implications for paleorecords that are hypothesized to represent monsoon variability, including many lake sediment records on the Tibetan Plateau. Monsoon precipitation in the Arabian Sea is distinct from precipitation in India and China, and increased precipitation in the Arabian Sea coincides with decreased precipitation in the western North Pacific. Furthermore, only precipitation in southwestern Tibet responds to the Southwest monsoon, whereas precipitation in southeastern Tibet responds to the western North Pacific monsoon. In southwestern Tibet, I have reconstructed dust variability over the last millennium using the lake sediment record from Kiang Co. The sediment record shows a trend toward increasing dust over the 20th century, and our hypothesized dust proxy is positively correlated with the June-November Arctic Oscillation Index. A trend toward more positive Arctic Oscillation Index values as well as higher temperatures over the 20th century likely drove increased dustiness in southwestern Tibet, due the influence of temperature on glaciofluvial sediment availability in the Himalayas. Sediment trap, sediment core data, and modern measurements of local climate and lake water variables at Genovesa Crater Lake, Galápagos, indicate the lake and its sediments respond to local climate variability, with carbonate-rich sediments forming during prolonged dry periods (La Niña events), and organic-rich sediment forming during the warm season and El Niño events. The ratios of silica to calcium and strontium to calcium also reflect cool season SST. Thus, this lake sediment record has potential to provide a record of both seasonal and ENSO variability spanning the Holocene.

East Pacific green sea turtles, Chelonia mydas, play ecologically important roles in marine habitats which range from grazing (and thus regularly "mowing") algae and seagrass beds to cycling nutrients between the ocean and land. However, these important grazers have been hunted to ecological extinction in some places for their eggs, meat, and skin. The conservation initiative for the survival of sea turtles requires the protection of their primary habitats in conjunction with a decrease in their interaction with humans. One way these objectives can be met is through the creation of species distribution maps (SDMs). For this thesis, a SDM was created from a generalized additive model used to identify major feeding areas for East Pacific green turtles residing in the Galapagos Islands. The input for the model was green turtle sighting locations during a June 2010 marine life observation survey and remotely sensed values of four oceanographic parameters obtained from satellite sensors (Bathymetry, Sea Surface Temperature, Chlorophyll a, and Current Speed). Line transects of intertidal and subtidal shoreline regions of the islands of Isabela, San Cristobal, and Floreana were also completed, to describe similarities and differences in macroalgal abundance between the locations. A generalized additive model (GAM) explained 56% of the data's null deviance and had a true positive rate of 0.83. The corresponding species distribution map indicated that East Pacific green sea turtles prefer to forage in warm, low chlorophyll a, slow moving waters at depths mostly less than 250m throughout the archipelago. ANOVA analyses showed that macroalgal abundance was statistically different (p-value < 0.01) between the islands of San Cristobal and Isabela. The line transects analysis also documented that red algae was the most prominent phyla at the sites and that the macroalgal abundance did not vary much between months June 2010 and April/May 2011. With these results, potential foraging areas for East Pacific green turtles can be identified and protected. Future studies will be focused on the collection of macroalgae from coastal areas outlined in the SDM and the interactions between green turtles and their competitors and/or predators. This information can be used to validate the areas delineated by the model and to further the understanding of the spatial-temporal effects on macroalgal abundance.

Understanding the dynamics of functional genetic variability in small populations can have important implications in their conservation. I screened the variation of MHC II gene in Galapagos mockingbirds to evaluate the evolutionary forces that shaped the genetic variation. I found out that genetic drift affected the MHC variation together with a specific form of natural selection. Although the MHC is supposed to be under a pathogen-mediated selection I found no evidence for this theory in the mockingbird study system.