Few studies utilise modern species distribution data and modeling to make predictions for examining potential fossil localities. Instead, species distribution modeling is often used for palaeoenvironmental interpretations. Using palaeoclimate data to model potential past distributions for a species provides a prediction showing areas where its fossil remains may be found. In this study, the current, Last Glacial Maximum, and Last Interglacial potential distributions of the arid steppe-obligate saiga antelope (Artiodactyla: Bovidae, Saiga tatarica) were modeled using the species distribution model Maxent. Few fossil records exist, but available fossil locality records were used to validate both palaeo models, resulting in speculative predictions about where the saiga may have lived. Known fossil localities of saiga from the Last Glacial Maximum time period were located within predicted moderately suitable environments, while four of seven Last Interglacial fossil localities were located within predicted moderately suitable environments, suggesting that models can accurately identify areas where fossils for the saiga can be found. Specifically, these models suggest saiga fossils may be located in northwestern and northeastern China, the western and central regions of the Middle East, and southern Alaska. The predicted areas in northeastern China are of particular interest because saiga fossils have not been identified in this region, but some palaeontologists theorize that northeast China may have been suitable for saiga in the past. The models lend credence to this argument.

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Chapter 1. The family Pteronarcyidae (Plecoptera) is a highly studied group of stoneflies and very important to a wide variety of aquatic studies. Several phylogenies have been proposed for this group recent decades, however there is little congruence between the various topologies. The present study revises the phylogeny of the group by combining molecular data from mitochondrial cytochrome oxidase subunit II, ribosomal subunit 12S, ribosomal subunit 16S, and nuclear loci ribosomal subinit 18S and Histone H3, with published morphological data in a parsimony-based total evidence analysis. The analysis produced a well-supported phylogeny with novel relationships within the genus Pteronarcys. Maximum Likelihood and Bayesian analyses produced topologies congruent with parsimony analysis. Character mapping revealed several homoplasious morphological characters that were previously thought to be homologous. Chapter 2. Phylogeographic studies in aquatic insects provide valuable insights into mechanisms that shape the genetic structure of aquatic communities. Yet studies that include broad geographic areas are uncommon for this group. We conducted a broad scale phylogeographic analysis of P. badia across western North America. In order to allow us to generate a larger mitochondrial data set, we used 454 seqeuncing to reconstruct the complete mitochondrial genome in the early stages of the project. Our analysis reveals what appears to be a complex history of isolation and multiple invasions among some lineages. The study provides evidence of multiple glacial refugia and suggests that historical climactic isolations have been important mechanisms in determining genetic structure of insects in western North America. Our ability to generate a large mitochondrial data set through mitochondrial genome reconstruction greatly improved nodal support of our mitochondrial gene tree, and allowed us to make stronger inference of relationships between lineages and timing of divergence events.

Excavations at Natural Trap Cave (NTC) began in the mid-1970's and quickly yielded evidence of a diverse steppe fauna that existed during the Last Glacial Maximum (MIS 2) along the western slope of the Bighorn Mountains in north central Wyoming. NTC is a karst pit cave with a 24.5 m vertical drop into a roughly 43 m wide bell-shaped ‘Main Chamber’ and during the course of early excavations a plugged entrance to a fossil-bearing ‘Lower Chamber’ was discovered. Stratigraphic relationships below the entrance to the Main Chamber of the cave were originally studied in the mid-1970's, but were never formally published. Although stratigraphy, taphonomy, and depositional circumstances were briefly discussed over the following years, little has been done to correlate the numerous stratigraphic schemes used by various authors. In this study, four stratigraphic sections were measured and analyzed to establish an easily modifiable lithostratigraphic system of nomenclature. We provide the first correlations of all stratigraphic nomenclature used throughout excavations at NTC to facilitate comparisons with current and previous collections and publications. By leveraging more than 100 radioisotopic dates we developed an age-depth model and chronostratigraphic framework to further interrogate spatiotemporal relationships between strata, paleoenvironmental proxies, and fossil assemblages. Deposition is shown to be discontinuous; sediment accumulation in the study area is restricted to the buildup through peak penultimate and Last Glacial maxima. More recent (<10 ka) Holocene deposits unconformably cover the eroded surface of underlying Pleistocene strata. There is active reworking of sediments with transport and deposition of reactivated material within the Lower Chamber. We note that the two hiatuses coincide with interglacial periods and may reflect changing depositional circumstances within the cave such as extended periods of non-deposition, erosion, or bypass (possibly leading to deposition in the Lower Chamber). Contrary to previous reports, we demonstrate that it is unlikely a prominent snow cone existed or contributed to the pattern of sediment and fossil distribution within the study area, furthermore, we do not observe a continuous Pleistocene-Holocene transition in the study area. Further stratigraphic work will be needed to better understand the interrelationship between Main and Lower chamber deposits and the evolution of sediment accumulation in NTC.

This thesis develops a better knowledge of the extent and timing of glaciations in southern Argentina throughout the Quaternary. It provides a detailed understanding of successive major glacial outlet lobes in the Lago Pueyrredón valley. The glacial and glaciofluvial deposits in the valley, as elsewhere in the region, are extremely well-preserved and reflect punctuated glacial advances between ~ 1.1 Ma and ~ 17 ka. Several intermediate glaciations are undated, constrained by the limited time frame of radiocarbon age dating, the limited potential volcanic sites for K-Ar or 40Ar/39Ar age dating, and erosion and exhumation problems associated with cosmogenic-nuclide surface exposure ages on moraines. This thesis provides a new chronology for the mid-Quaternary glaciations based on methodological advances in cosmogenic-nuclide surface exposure age dating. This is done by deriving ages from glacial outwash terrace sediment and demonstrating their reliability. The work shows that for younger (i.e., last glacial) moraines, well-constrained ages can be derived from the common-practice of dating large boulders on the moraine surface. However, on older moraines, the ages so-derived become considerably scattered. This is interpreted to be caused primarily by boulder exhumation as a consequence of moraine erosion, resulting in shorter residence of some boulders at the surface relative to the moraine formation date. By contrast, glacial outwash surfaces in this area, if carefully chosen, can be shown to have undergone little aggradation or erosion, and thus have had long and consistent surface exposure since formation. Provided these surfaces can be stratigraphically linked with the glacial limits, they can provide good surface exposure ages. This has been convincingly confirmed in one location by a sequence of ages obtained from a 10Be concentration depth-profile which demonstrate the surface stability and lack of inherited nuclides. Using these methods, cosmogenic 10Be and 26Al surface exposure ages indicate successive major advances occurred at ~ 1.2 Ma, ~ 600 ka, ~ 260 ka and ~27 – 17.5 ka. These are correlated with global marine and ice core records.

<b>Cardamine hirsuta</b> L. is an emerging model system in developmental genetics, where natural genetic variation within <b>C. hirsuta</b> provides the means to investigate the genetic basis of morphological traits. This thesis investigates the geographical structure and genealogical history of genetic variation within <b>C. hirsuta</b> and identifies its closest relatives. This will enable the accurate selection of species for comparison with <b>C. hirsuta</b> when making interpretations of evolutionary processes, and provide a better understanding of morphological character evolution in <b>C. hirsuta</b>. The phylogeographic history of <b>C. hirsuta</b> was reconstructed using multiple chloroplast and nuclear markers and widespread accession sampling from across its native range. A distinct group was identified within <b>C. hirsuta</b>, restricted to the high mountains of East Africa. Climate suitability modelling showed that Pleistocene glacial dynamics have had a strong effect on the distribution of genetic variation within <b>C. hirsuta</b>. The phylogeographical data generated here was used to investigate the origin of <b>C. hirsuta</b> in the Azores, an oceanic archipelago. The Azores are dominated by an endemic chloroplast haplotype which is associated with an endemic phenotype. Thus, <b>C. hirsuta</b> appears to have diversified <b>in situ</b> in the Azores. Phylogenetic analyses of Cardamine, restricted to diploid species to remove the confounding effects of polyploids, found that <b>C. hirsuta</b> is most closely related to <b>C. oligosperma</b>, a western North American species. Multiple loci and extensive intraspecific sampling were brought to bear to demonstrate that <b>C. hirsuta</b> and <b>C. oligosperma</b> are reciprocally monophyletic. <b>Cardamine pattersonii</b>, a restricted endemic from north-west Oregon is likely to be an allopolyploid, with <b>C. oligosperma</b> as the maternal parent and possibly <b>C. nuttallii</b> as the paternal parent.

Este estudo apresenta indicações de mudanças paleoceanográficas ao longo dos últimos 25.000 anos na porção oeste do Oceano Atlântico Sul a partir do registro da variação de nanofósseis calcários em dois testemunhos de sedimento marinho da margem continental nordeste do Brasil. Outros indicadores foram incorporados às análises de nanofósseis calcários no intuito de melhor compreender as alterações observadas nas assembléias fósseis: 1) dados isotópicos de oxigênio de testas de foraminíferos planctônicos e bentônicos; 2) índice de temperatura e de nutrientes; 3) equação de paleoprodutividade e 4) análises estatísticas multivariadas. Os índices de temperatura e nutrientes foram, pela primeira vez, aplicados a nanofósseis calcários do Quaternário em amostras do Atlântico Sul. A integração dos resultados sugere que as principais características oceanográficas não sofreram alterações significativas nos últimos 25.000 anos, embora condições ambientais instáveis tenham sido registradas a partir da transição do Último Máximo Glacial - Holoceno. Durante o Último Máximo Glacial a região estudada sofreu pouca variação de temperatura, funcionando como um reservatório de calor. A variação da profundidade da termoclina/nutriclina foi considerada a principal resposta às oscilações climáticas, sendo relacionada às mudanças de intensidade dos ventos alísios. / This study focuses on changes in calcareous nannofossil assemblages as an evidence of paleoceanographic variability during the last 25,000 years in two deep sea piston cores from the northeastern Brazilian continental margin. To support reconstructing ancient marine environment others proxies have been applied along with the calcareous nannofossil analysis: 1) oxygen isotopic data from planktonic and benthic foraminifers\' tests; 2) temperature and nutrient indices; 3) paleoproductivity equation and 4) multivariate analysis. For the first time the temperature and nutrient indices were employed to Quaternary calcareous nannofossil from the South Atlantic Ocean. According to presented results major oceanographic features were stable in the last 25,000 years, although instable environmental conditions were recorded in the Last Glacial Maximum - Holocene boundary. During the Last Glacial Maximum the western tropical Atlantic seems to have experienced slight temperature changes and served as a heat and salt reservoir. Nutricline and thermocline depth variation was considered the most important response to climate changes largely related to Trade Winds strength oscillation.

As assembléias dos foraminíferos planctônicos fósseis de dois testemunhos amostrados do Atlântico tropical oeste representativo dos últimos 30.000 anos foram analisadas junto com estimativas de paleotemperatura superficial e &#8706;18O e &#8706;13C do foraminífero planctônico Globigerinoides ruber \'branca\'. Estes resultados mostraram que durante o Último Máximo Glacial e durante os eventos de resfriamento de curta duração Heinrich 1 and Younger Dryas o Atlântico tropical oeste manteve altas paleotemperaturas superficiais. Este estudo sugere que durante este período o Atlântico tropical oeste ocorreu uma acumulação de sal e clor nesta porção do Atlântico como conseqüência do enfraqueciemnto do transporte de calor e sal através do equador. Ao final destes eventos a intensificação do transporte de calor e sal foi restabelecido, baixando a temperatura superficial aos valores conhecidos atuamente. Este estudo sugere que o Atlântico tropical oeste atuou como um reservatório de calor e sal durante a deglaciação. / The planktonic foraminiferal assemblages of two piston cores from western tropical Atlantic covering the last 30,000 years have been analysed together with paleoceanographic ANN sea surface temperature reconstruction and ?18O and ?13C of the shallow dwelling planntonic foraminifera Globigerinoides ruber \'white\'. These proxies reveal that during the Last Glacial Maximum and during the Heinrich 1 and Younger Dryas cold events, the western tropical experienced warm periods. This study suggest that during these warm intervals a pronounced accumulation of heat and salt occurred at western tropical Atlantic, as a result of cross-equatorial heat and salt transport decrease. At the end of these events, the intensification of cross-equatorial heat and salt transport cooled and freshened the western tropical surface waters. This study suggests the western tropical Atlantic served as a heat and salt reservoir during deglaciation.

Parasitism in plants is often accompanied by a suite of morphological and physiological changes resulting in a condition known as the ‘parasitic reduction syndrome’. With changes including extreme vegetative reduction, frequently beyond any resemblance to its photosynthetic relatives, accompanied by significant losses of genes linked to photosynthesis, the study of parasitic plants can be challenging. Conopholis (Orobanchaceae) is a small holoparasitic genus distributed across eastern and southwestern North America and Central America. This genus has never been the subject of a molecular phylogenetic or morphometric analyses. In addition, very little is known of the relationships among populations and of their post-glacial history. To investigate the species limits and phylogenetic relationships in Conopholis, we conducted a comprehensive molecular phylogenetic study of the genus as well as a fine-scale morphometric study. Based on plastid and nuclear sequences, Conopholis was found to contain three distinct and well-supported lineages which have varying degrees of overlap with previously proposed taxa. The clustering and ordination analyses of the morphometric study corroborated the molecular data, demonstrating the morphological differentiation between the three lineages detected within Conopholis. A taxonomic re-alignment is proposed for the genus that recognizes three species, C. americana, C. panamensis, and C. alpina. To address genetic diversity and phylogeographic structure of C. americana in eastern North America, microsatellite markers were developed and characterized for the first time in this species. Using these newly generated markers along with sequences from the plastid genome, the persistence of a minimum of two glacial refugia at the last glacial maximum were inferred, one in Florida and southern Alabama and another in the Appalachian Mountains near the southern tip of Blue Ridge Mountains. The diversity seen across the southern Appalachian Mountains supports the hypothesis that populations derived from the southern and northern refugia come together in this area.