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Jamieson SSR, Ross N, Paxman GJG, Clubb FJ, Young DA, Yan S, Greenbaum J, Blankenship DD, Siegert MJ. An ancient river landscape preserved beneath the East Antarctic Ice Sheet. Nat Commun 2023; 14:6507. [PMID: 37875503 PMCID: PMC10597991 DOI: 10.1038/s41467-023-42152-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 10/02/2023] [Indexed: 10/26/2023] Open
Abstract
The East Antarctic Ice Sheet (EAIS) has its origins ca. 34 million years ago. Since then, the impact of climate change and past fluctuations in the EAIS margin has been reflected in periods of extensive vs. restricted ice cover and the modification of much of the Antarctic landscape. Resolving processes of landscape evolution is therefore critical for establishing ice sheet history, but it is rare to find unmodified landscapes that record past ice conditions. Here, we discover an extensive relic pre-glacial landscape preserved beneath the central EAIS despite millions of years of ice cover. The landscape was formed by rivers prior to ice sheet build-up but later modified by local glaciation before being dissected by outlet glaciers at the margin of a restricted ice sheet. Preservation of the relic surfaces indicates an absence of significant warm-based ice throughout their history, suggesting any transitions between restricted and expanded ice were rapid.
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Affiliation(s)
| | - Neil Ross
- School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
| | - Guy J G Paxman
- Department of Geography, Durham University, Durham, DH1 3LE, UK
| | - Fiona J Clubb
- Department of Geography, Durham University, Durham, DH1 3LE, UK
| | - Duncan A Young
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, USA
| | - Shuai Yan
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, USA
- Department of Geosciences, Jackson School of Geosciences, University of Texas at Austin, Austin, USA
| | - Jamin Greenbaum
- Scripps Institute for Oceanography, University of California at San Diego, San Diego, USA
| | - Donald D Blankenship
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, USA
| | - Martin J Siegert
- Tremough House, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
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2
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Akagi K, Koizumi K, Kadowaki M, Kitajima I, Saito S. New Possibilities for Evaluating the Development of Age-Related Pathologies Using the Dynamical Network Biomarkers Theory. Cells 2023; 12:2297. [PMID: 37759519 PMCID: PMC10528308 DOI: 10.3390/cells12182297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 09/12/2023] [Accepted: 09/15/2023] [Indexed: 09/29/2023] Open
Abstract
Aging is the slowest process in a living organism. During this process, mortality rate increases exponentially due to the accumulation of damage at the cellular level. Cellular senescence is a well-established hallmark of aging, as well as a promising target for preventing aging and age-related diseases. However, mapping the senescent cells in tissues is extremely challenging, as their low abundance, lack of specific markers, and variability arise from heterogeneity. Hence, methodologies for identifying or predicting the development of senescent cells are necessary for achieving healthy aging. A new wave of bioinformatic methodologies based on mathematics/physics theories have been proposed to be applied to aging biology, which is altering the way we approach our understand of aging. Here, we discuss the dynamical network biomarkers (DNB) theory, which allows for the prediction of state transition in complex systems such as living organisms, as well as usage of Raman spectroscopy that offers a non-invasive and label-free imaging, and provide a perspective on potential applications for the study of aging.
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Affiliation(s)
- Kazutaka Akagi
- Research Center for Pre-Disease Science, University of Toyama, Toyama 930-8555, Japan
| | - Keiichi Koizumi
- Research Center for Pre-Disease Science, University of Toyama, Toyama 930-8555, Japan
- Division of Presymptomatic Disease, Institute of Natural Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Makoto Kadowaki
- Research Center for Pre-Disease Science, University of Toyama, Toyama 930-8555, Japan
| | - Isao Kitajima
- Research Center for Pre-Disease Science, University of Toyama, Toyama 930-8555, Japan
| | - Shigeru Saito
- Research Center for Pre-Disease Science, University of Toyama, Toyama 930-8555, Japan
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3
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Hu C, Jiao Z, Deng X, Tu X, Lu A, Xie C, Jiang K, Zeng X, Liu ZJ, Huang W, Luo Y. The ecological adaptation of the unparalleled plastome character evolution in slipper orchids. FRONTIERS IN PLANT SCIENCE 2022; 13:1075098. [PMID: 36605947 PMCID: PMC9808092 DOI: 10.3389/fpls.2022.1075098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
Plastomes may have undergone adaptive evolution in the process of plant adaptation to diverse environments, whereby species may differ in plastome characters. Cypripedioideae successfully colonized distinct environments and could be an ideal group for studying the interspecific variation and adaptive evolution of plastomes. Comparative study of plastomes, ancestral state reconstruction, phylogenetic-based analysis, ecological niche modelling, and selective pressure analysis were conducted to reveal the evolutionary patterns of plastomes in Cypripedioideae and their relationship with environmental factors. The plastomes of the three evolved genera had reduced plastome size, increased GC content, and compacted gene content compared to the basal group. Variations in plastome size and GC content are proved to have clear relationships with climate regions. Furthermore, ecological niche modelling revealed that temperature and water factors are important climatic factors contributing to the distributional difference which is directly correlated with the climate regions. The temperature-sensitive genes ndh genes, infA, and rpl20 were found to be either lost/pseudogenized or under positive selection in the evolved groups. Unparalleled plastome character variations were discovered in slipper orchids. Our study indicates that variations in plastome characters have adaptive consequences and that temperature and water factors are important climatic factors that affect plastome evolution. This research highlights the expectation that plants can facilitate adaptation to different environmental conditions with the changes in plastome and has added critical insight for understanding the process of plastome evolution in plants.
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Affiliation(s)
- Chao Hu
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhenbin Jiao
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xinyan Deng
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China
| | - Xiongde Tu
- College of Forestry, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Aixian Lu
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China
- Key Laboratory of Orchid Conservation and Utilization of National Forestry and Grassland Administration at College of Landscape Architecture and Art, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Chengzhi Xie
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China
| | - Kai Jiang
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China
| | - Xinhua Zeng
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China
| | - Zhong-Jian Liu
- Key Laboratory of Orchid Conservation and Utilization of National Forestry and Grassland Administration at College of Landscape Architecture and Art, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Weichang Huang
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China
| | - Yibo Luo
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- China National Botanical Garden, Beijing, China
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4
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A comparative and ontogenetic examination of mitochondrial function in Antarctic notothenioid species. J Comp Physiol B 2022; 192:737-750. [PMID: 36104549 PMCID: PMC9550766 DOI: 10.1007/s00360-022-01461-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 07/25/2022] [Accepted: 08/30/2022] [Indexed: 12/03/2022]
Abstract
Notothenioidei fishes have evolved under stable cold temperatures; however, ocean conditions are changing globally, with polar regions poised to experience the greatest changes in environmental factors, such as warming. These stressors have the potential to dramatically affect energetic demands, and the persistence of the notothenioids will be dependent on metabolic capacity, or the ability to match energy supply with energy demand, to restore homeostasis in the face of changing climate conditions. In this study we examined aerobic metabolic capacity in three species, Trematomus bernacchii, T. pennellii and T. newnesi, and between two life stages, juvenile and adult, by assessing mitochondrial function of permeabilized cardiac fibers. Respiratory capacity differed among the adult notothenioids in this study, with greater oxidative phosphorylation (OXPHOS) respiration in the pelagic T. newnesi than the benthic T. bernacchii and T. pennellii. The variation in mitochondrial respiratory capacity was likely driven by differences in the mitochondrial content, as measured by citrate synthase activity, which was the highest in T. newnesi. In addition to high OXPHOS, T. newnesi exhibited lower LEAK respiration, resulting in greater mitochondrial efficiency than either T. bernacchii or T. pennellii. Life stage largely had an effect on mitochondrial efficiency and excess complex IV capacity, but there were little differences in OXPHOS respiration and electron transfer capacity, pointing to a lack of significant differences in the metabolic capacity between juveniles and adults. Overall, these results demonstrate species-specific differences in cardiac metabolic capacity, which may influence the acclimation potential of notothenioid fishes to changing environmental conditions.
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Meckler AN, Sexton PF, Piasecki AM, Leutert TJ, Marquardt J, Ziegler M, Agterhuis T, Lourens LJ, Rae JWB, Barnet J, Tripati A, Bernasconi SM. Cenozoic evolution of deep ocean temperature from clumped isotope thermometry. Science 2022; 377:86-90. [PMID: 35771913 DOI: 10.1126/science.abk0604] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Characterizing past climate states is crucial for understanding the future consequences of ongoing greenhouse gas emissions. Here, we revisit the benchmark time series for deep ocean temperature across the past 65 million years using clumped isotope thermometry. Our temperature estimates from the deep Atlantic Ocean are overall much warmer compared with oxygen isotope-based reconstructions, highlighting the likely influence of changes in deep ocean pH and/or seawater oxygen isotope composition on classical oxygen isotope records of the Cenozoic. In addition, our data reveal previously unrecognized large swings in deep ocean temperature during early Eocene acute greenhouse warmth. Our results call for a reassessment of the Cenozoic history of ocean temperatures to achieve a more accurate understanding of the nature of climatic responses to tectonic events and variable greenhouse forcing.
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Affiliation(s)
- A N Meckler
- Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway
| | - P F Sexton
- School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, UK
| | - A M Piasecki
- Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway
| | - T J Leutert
- Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway
| | - J Marquardt
- Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway
| | - M Ziegler
- Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - T Agterhuis
- Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - L J Lourens
- Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - J W B Rae
- School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, UK
| | - J Barnet
- School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, UK
| | - A Tripati
- Department of Earth, Planetary, and Space Science, Department of Atmospheric and Oceanic Science, Institute of the Environment and Sustainability, American Indian Studies Center, Center for Diverse Leadership in Science, University of California, Los Angeles, Los Angeles, USA
| | - S M Bernasconi
- Department of Earth Science, ETH Zürich, Zürich, Switzerland
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6
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Effects of noise correlation and imperfect data sampling on indicators of critical slowing down. THEOR ECOL-NETH 2022. [DOI: 10.1007/s12080-022-00532-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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7
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Paleogeography control of Indian monsoon intensification and expansion at 41 Ma. Sci Bull (Beijing) 2021; 66:2320-2328. [PMID: 36654458 DOI: 10.1016/j.scib.2021.07.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 06/20/2021] [Accepted: 06/22/2021] [Indexed: 02/03/2023]
Abstract
As a crucial part of the Asian monsoon stretching from tropical India to temperate East Asia, the Indian monsoon (IM) contributes predominant precipitation over Asian continent. However, our understanding of IM's onset, development and the underlying driving mechanisms is limited. Increasing evidence indicates that the IM began in the Eocene or even the Paleocene and was unexceptionally linked to the early rise of the Tibetan Plateau (TP). These were challenged by the heterogeneous and diachronous uplift of the TP and all the reported records were confined to tropical zone under tropical monsoon driven by the Intertropical Convergence Zone (ITCZ) that is irrelevant to the TP. Therefore, reliable paleoclimatic records from the extra-tropical IM region is crucial to reveal how the tropical IM expanded to subtropical and temperate zones and what driving factors might be related to it. Here we present robust Eocene paleoenvironmental records from central Yunnan (~26°N) in subtropical East Asia. The multiproxy results of two sites demonstrate a consistent sudden switch from a dry environment in the early Eocene to a seasonally wet one at 41 Ma, suggesting a jump of the tropical IM to the southern subtropical zone at 41 Ma. The full collision of India with Asia, and the resulting changes in paleogeography at 41 Ma (closure of the Neotethys sea, retreat of the Paratethys seas, fast northward movement of the southern margin of the TP and rise of the central TP), aided by synchronous Antarctic cooling, might have worked together to drive the IM enhancement and northward expansion.
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8
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Laitinen V, Dakos V, Lahti L. Probabilistic early warning signals. Ecol Evol 2021; 11:14101-14114. [PMID: 34707843 PMCID: PMC8525087 DOI: 10.1002/ece3.8123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 07/23/2021] [Accepted: 08/31/2021] [Indexed: 12/05/2022] Open
Abstract
Ecological communities and other complex systems can undergo abrupt and long-lasting reorganization, a regime shift, when deterministic or stochastic factors bring them to the vicinity of a tipping point between alternative states. Such changes can be large and often arise unexpectedly. However, theoretical and experimental analyses have shown that changes in correlation structure, variance, and other standard indicators of biomass, abundance, or other descriptive variables are often observed prior to a state shift, providing early warnings of an anticipated transition. Natural systems manifest unknown mixtures of ecological and environmental processes, hampered by noise and limited observations. As data quality often cannot be improved, it is important to choose the best modeling tools available for the analysis.We investigate three autoregressive models and analyze their theoretical differences and practical performance. We formulate a novel probabilistic method for early warning signal detection and demonstrate performance improvements compared to nonprobabilistic alternatives based on simulation and publicly available experimental time series.The probabilistic formulation provides a novel approach to early warning signal detection and analysis, with enhanced robustness and treatment of uncertainties. In real experimental time series, the new probabilistic method produces results that are consistent with previously reported findings.Robustness to uncertainties is instrumental in the common scenario where mechanistic understanding of the complex system dynamics is not available. The probabilistic approach provides a new family of robust methods for early warning signal detection that can be naturally extended to incorporate variable modeling assumptions and prior knowledge.
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Affiliation(s)
| | - Vasilis Dakos
- Institut des Sciences de l’Evolution de Montpellier (ISEM)University of MontpellierMontpellierFrance
| | - Leo Lahti
- Department of ComputingUniversity of TurkuTurkuFinland
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Kim SL, Zeichner SS, Colman AS, Scher HD, Kriwet J, Mörs T, Huber M. Probing the Ecology and Climate of the Eocene Southern Ocean With Sand Tiger Sharks Striatolamia macrota. PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY 2020; 35:e2020PA003997. [PMID: 34222817 PMCID: PMC8246854 DOI: 10.1029/2020pa003997] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 10/20/2020] [Accepted: 11/01/2020] [Indexed: 06/13/2023]
Abstract
Many explanations for Eocene climate change focus on the Southern Ocean-where tectonics influenced oceanic gateways, ocean circulation reduced heat transport, and greenhouse gas declines prompted glaciation. To date, few studies focus on marine vertebrates at high latitudes to discern paleoecological and paleoenvironmental impacts of this climate transition. The Tertiary Eocene La Meseta (TELM) Formation has a rich fossil assemblage to characterize these impacts; Striatolamia macrota, an extinct (†) sand tiger shark, is abundant throughout the La Meseta Formation. Body size is often tracked to characterize and integrate across multiple ecological dimensions. †S. macrota body size distributions indicate limited changes during TELMs 2-5 based on anterior tooth crown height (n = 450, mean = 19.6 ± 6.4 mm). Similarly, environmental conditions remained stable through this period based on δ18OPO4 values from tooth enameloid (n = 42; 21.5 ± 1.6‰), which corresponds to a mean temperature of 22.0 ± 4.0°C. Our preliminary ε Nd (n = 4) results indicate an early Drake Passage opening with Pacific inputs during TELM 2-3 (45-43 Ma) based on single unit variation with an overall radiogenic trend. Two possible hypotheses to explain these observations are (1) †S. macrota modified its migration behavior to ameliorate environmental changes related to the Drake Passage opening, or (2) the local climate change was small and gateway opening had little impact. While we cannot rule out an ecological explanation, a comparison with climate model results suggests that increased CO2 produces warm conditions that also parsimoniously explain the observations.
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Affiliation(s)
- Sora L. Kim
- Department of Geophysical SciencesUniversity of ChicagoChicagoILUSA
- Department of Life and Environmental SciencesUniversity of CaliforniaMercedCAUSA
| | - Sarah S. Zeichner
- Department of Geophysical SciencesUniversity of ChicagoChicagoILUSA
- Division of Geological and Planetary SciencesCalifornia Institute of TechnologyPasadenaCAUSA
| | - Albert S. Colman
- Department of Geophysical SciencesUniversity of ChicagoChicagoILUSA
- Department of Earth, Environment, and Planetary SciencesRice UniversityHoustonTXUSA
| | - Howie D. Scher
- Department of Earth, Ocean, and EnvironmentUniversity of South CarolinaColumbiaSCUSA
| | - Jürgen Kriwet
- Department of PalaeontologyUniversity of ViennaViennaAustria
| | - Thomas Mörs
- Department of PalaeobiologySwedish Museum of Natural HistoryStockholmSweden
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
| | - Matthew Huber
- Department of Earth, Atmosphere, and Planetary SciencesPurdue UniversityWest LafayetteINUSA
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Li F, Li S. Paleocene–Eocene and Plio–Pleistocene sea-level changes as “species pumps” in Southeast Asia: Evidence from Althepus spiders. Mol Phylogenet Evol 2018; 127:545-555. [DOI: 10.1016/j.ympev.2018.05.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 04/28/2018] [Accepted: 05/13/2018] [Indexed: 01/03/2023]
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11
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Díaz A, Gérard K, González-Wevar C, Maturana C, Féral JP, David B, Saucède T, Poulin E. Genetic structure and demographic inference of the regular sea urchin Sterechinus neumayeri (Meissner, 1900) in the Southern Ocean: The role of the last glaciation. PLoS One 2018; 13:e0197611. [PMID: 29874287 PMCID: PMC5991379 DOI: 10.1371/journal.pone.0197611] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 05/04/2018] [Indexed: 01/10/2023] Open
Abstract
One of the most relevant characteristics of the extant Southern Ocean fauna is its resiliency to survive glacial processes of the Quaternary. These climatic events produced catastrophic habitat reductions and forced some marine benthic species to move, adapt or go extinct. The marine benthic species inhabiting the Antarctic upper continental shelf faced the Quaternary glaciations with different strategies that drastically modified population sizes and thus affected the amount and distribution of intraspecific genetic variation. Here we present new genetic information for the most conspicuous regular sea urchin of the Antarctic continental shelf, Sterechinus neumayeri. We studied the patterns of genetic diversity and structure in this broadcast-spawner across three Antarctic regions: Antarctic Peninsula, the Weddell Sea and Adélie Land in East Antarctica. Genetic analyses based on mitochondrial and nuclear markers suggested that S. neumayeri is a single genetic unit around the Antarctic continent. The species is characterized by low levels of genetic diversity and exhibits a typical star-like haplotype genealogy that supports the hypothesis of a single in situ refugium. Based on two mutation rates standardized for this genus, the Bayesian Skyline plot analyses detected a rapid demographic expansion after the Last Glacial Maximum. We propose a scenario of rapid postglacial expansion and recolonization of Antarctic shallow areas from a less ice-impacted refugium where the species survived the LGM. Considering the patterns of genetic diversity and structure recorded in the species, this refugium was probably located in East Antarctica.
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Affiliation(s)
- Angie Díaz
- Departamento de Zoología, Universida d de Concepción, Barrio Universitario s/n, Concepción, Chile
| | - Karin Gérard
- Facultad de Ciencias, Universidad de Magallanes, Bulnes, Punta Arenas, Chile
- Laboratorio de Ecología Molecular Antártica y Subantártica, Universidad de Magallanes, Punta Arenas, Chile
| | - Claudio González-Wevar
- Laboratorio de Ecología Molecular Antártica y Subantártica, Universidad de Magallanes, Punta Arenas, Chile
- Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
- Instituto de Ecología y Biodiversidad (IEB), Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras, Ñuñoa, Santiago, Chile
| | - Claudia Maturana
- Instituto de Ecología y Biodiversidad (IEB), Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras, Ñuñoa, Santiago, Chile
| | - Jean-Pierre Féral
- UMR 7263—IMBE, Station Marine d’Endoume, Institut Méditerranéen de Biodiversité et d’Ecologie Marine et continentale, Chemin de la Batterie des Lions,Marseille, France
| | - Bruno David
- Biogéosciences, UMR CNRS 6282, Université de Bourgogne, boulevard Gabriel, Dijon, France
- Museum National d’Histoire Naturelle, Paris, France
| | - Thomas Saucède
- UMR 7263—IMBE, Station Marine d’Endoume, Institut Méditerranéen de Biodiversité et d’Ecologie Marine et continentale, Chemin de la Batterie des Lions,Marseille, France
| | - Elie Poulin
- Instituto de Ecología y Biodiversidad (IEB), Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras, Ñuñoa, Santiago, Chile
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Abstract
Earth’s modern climate is defined by the presence of ice at both poles, but that ice is now disappearing. Therefore understanding the origin and causes of polar ice stability is more critical than ever. Here we provide novel geochemical data that constrain past dynamics of glacial ice on Greenland and Arctic sea ice. Based on accurate source determinations of individual ice-rafted Fe-oxide grains, we find evidence for episodic glaciation of distinct source regions on Greenland as far-ranging as ~68°N and ~80°N synchronous with ice-rafting from circum-Arctic sources, beginning in the middle Eocene. Glacial intervals broadly coincide with reduced CO2, with a potential threshold for glacial ice stability near ~500 p.p.m.v. The middle Eocene represents the Cenozoic onset of a dynamic cryosphere, with ice in both hemispheres during transient glacials and substantial regional climate heterogeneity. A more stable cryosphere developed at the Eocene-Oligocene transition, and is now threatened by anthropogenic emissions. With rapidly disappearing ice, understanding the past behavior of the cryosphere is critical. Here, the authors indicate the initiation and disappearance of glaciation on Greenland and Arctic sea ice coincided in the past, synchronous with Antarctic ice and global ice volume, and a CO2 threshold of ~500 p.p.m.v.
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13
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Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic. Proc Natl Acad Sci U S A 2016; 113:11782-11787. [PMID: 27698116 DOI: 10.1073/pnas.1608100113] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Growth of the first permanent Antarctic ice sheets at the Eocene-Oligocene Transition (EOT), ∼33.7 million years ago, indicates a major climate shift within long-term Cenozoic cooling. The driving mechanisms that set the stage for this glaciation event are not well constrained, however, owing to large uncertainties in temperature reconstructions during the Eocene, especially at lower latitudes. To address this deficiency, we used recent developments in coccolith biogeochemistry to reconstruct equatorial Atlantic sea surface temperature (SST) and atmospheric pCO2 values from pelagic sequences preceding and spanning the EOT. We found significantly more variability in equatorial SSTs than previously reported, with pronounced cooling from the Early to Middle Eocene and subsequent warming during the Late Eocene. Thus, we show that the Antarctic glaciation at the Eocene-Oligocene boundary was preceded by a period of heat accumulation in the low latitudes, likely focused in a progressively contracting South Atlantic gyre, which contributed to cooling high-latitude austral regions. This prominent redistribution of heat corresponds to the emplacement of a strong meridional temperature gradient that typifies icehouse climate conditions. Our equatorial coccolith-derived geochemical record thus highlights an important period of global climatic and oceanic upheaval, which began 4 million years before the EOT and, superimposed on a long-term pCO2 decline, drove the Earth system toward a glacial tipping point in the Cenozoic.
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Kikkawa E, Tanaka M, Naruse TK, Tsuda TT, Tsuda M, Murata K, Kimura A. Diversity of MHC class I alleles in Spheniscus humboldti. Immunogenetics 2016; 69:113-124. [PMID: 27654451 DOI: 10.1007/s00251-016-0951-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 09/10/2016] [Indexed: 10/21/2022]
Abstract
The major histocompatibility complex locus (MHC) is a gene region related to immune response and exhibits a remarkably great diversity. We deduced that polymorphisms in MHC genes would help to solve several issues on penguins, including classification, phylogenetic relationship, and conservation. This study aimed to elucidate the structure and diversity of the so far unknown MHC class I gene in a penguin species. The structure of an MHC class I gene from the Humboldt penguin (Spheniscus humboldti) was determined by using an inverse PCR method. We designed PCR primers to directly determine nucleotide sequences of PCR products from the MHC class I gene and to obtain recombinant clones for investigating the diversity of the MHC class I gene in Humboldt penguins. A total of 24 MHC class I allele sequences were obtained from 40 individuals. Polymorphisms were mainly found in exons 2 and 3, as expected from the nature of MHC class I genes in vertebrate species including birds and mammals. Phylogenetic analyses of MHC class I alleles have revealed that the Humboldt penguin is closely related to the Red Knot (Calidris canutus) belonging to Charadriiformes.
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Affiliation(s)
- Eri Kikkawa
- College of Bioresource Sciences, Nihon University, Tokyo, Japan.,Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Masafumi Tanaka
- Division of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, Isehara, Japan
| | - Taeko K Naruse
- Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
| | - Tomi T Tsuda
- Division of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, Isehara, Japan.,Human Life Science, Tokushima Bunri University, Tokushima, Japan
| | - Michio Tsuda
- Division of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, Isehara, Japan
| | - Koichi Murata
- College of Bioresource Sciences, Nihon University, Tokyo, Japan
| | - Akinori Kimura
- Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
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Loyd SJ, Sample J, Tripati RE, Defliese WF, Brooks K, Hovland M, Torres M, Marlow J, Hancock LG, Martin R, Lyons T, Tripati AE. Methane seep carbonates yield clumped isotope signatures out of equilibrium with formation temperatures. Nat Commun 2016; 7:12274. [PMID: 27447820 PMCID: PMC4961868 DOI: 10.1038/ncomms12274] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 06/17/2016] [Indexed: 11/29/2022] Open
Abstract
Methane cold seep systems typically exhibit extensive buildups of authigenic carbonate minerals, resulting from local increases in alkalinity driven by methane oxidation. Here, we demonstrate that modern seep authigenic carbonates exhibit anomalously low clumped isotope values (Δ47), as much as ∼0.2‰ lower than expected values. In modern seeps, this range of disequilibrium translates into apparent temperatures that are always warmer than ambient temperatures, by up to 50 °C. We examine various mechanisms that may induce disequilibrium behaviour in modern seep carbonates, and suggest that the observed values result from several factors including kinetic isotopic effects during methane oxidation, mixing of inorganic carbon pools, pH effects and rapid precipitation. Ancient seep carbonates studied here also exhibit potential disequilibrium signals. Ultimately, these findings indicate the predominance of disequilibrium clumped isotope behaviour in modern cold seep carbonates that must be considered when characterizing environmental conditions in both modern and ancient cold seep settings. The geochemistry of methane cold seep carbonates is often used to reconstruct environmental conditions. Loyd et al. find disequilibrium clumped isotope compositions in modern seep carbonates that suggest temperatures up to 50°C too high, raising doubt on seep carbonate temperature reconstructions.
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Affiliation(s)
- S J Loyd
- Department of Geological Sciences, California State University, Fullerton, California 92831, USA.,Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, California 90095, USA
| | - J Sample
- School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, Arizona 86001, USA
| | - R E Tripati
- Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, California 90095, USA.,Department of Atmospheric and Oceanic Sciences, Institute of the Environment and Sustainability, University of California, Los Angeles, California 90095, USA.,European Institute of Marine Sciences (IUEM), Université de Brest, UMR 6538/6539, Rue Dumont D'Urville, and IFREMER, Plouzané 29019, France
| | - W F Defliese
- Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, California 90095, USA
| | - K Brooks
- Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, California 90095, USA
| | - M Hovland
- Centre for Geobiology, University of Bergen, Bergen 5003, Norway
| | - M Torres
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - J Marlow
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
| | - L G Hancock
- Department of Earth Sciences, University of California, Riverside, California 92521, USA
| | - R Martin
- Department of Earth and Space Sciences/Burke Museum, University of Washington, Seattle, Washington 98195, USA
| | - T Lyons
- Department of Earth Sciences, University of California, Riverside, California 92521, USA
| | - A E Tripati
- Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, California 90095, USA.,Department of Atmospheric and Oceanic Sciences, Institute of the Environment and Sustainability, University of California, Los Angeles, California 90095, USA.,European Institute of Marine Sciences (IUEM), Université de Brest, UMR 6538/6539, Rue Dumont D'Urville, and IFREMER, Plouzané 29019, France
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16
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Bosboom R, Mandic O, Dupont-Nivet G, Proust JN, Ormukov C, Aminov J. Late Eocene palaeogeography of the proto-Paratethys Sea in Central Asia (NW China, southern Kyrgyzstan and SW Tajikistan). ACTA ACUST UNITED AC 2015. [DOI: 10.1144/sp427.11] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractThe Cretaceous and Palaeogene sediments of the basins in Central Asia include the remnants of the easternmost extent of a vast shallow epicontinental sea, which extended across the Eurasian continent before it retreated westwards and eventually isolated as the Paratethys Sea. To improve understanding of its long-term palaeogeographical evolution, we complement the well-constrained chronological framework of the Tarim Basin in China with stratigraphic records of the sea retreat from the Fergana Basin and the Alai Valley Basin in southern Kyrgyzstan and the Afghan–Tajik Basin in SW Tajikistan. By lithostratigraphic analyses and identification of bivalve assemblages, this study establishes for the first time a clear and detailed regional correlation of Palaeogene marine strata across Central Asia, showing that the basins share a similar palaeogeographical evolution characterized by a long-term stepwise retreat punctuated by short-term shallow-marine incursions. Our correlation shows that the last two marine incursions recognized in the Tarim Basin can be traced westwards. The permanent disappearance of the sea from Central Asia probably occurred with limited diachroneity in the late Eocene, before the isolation of the Paratethys Sea, shifting the easternmost margin of the sea hundreds of kilometres westwards and probably significantly reducing moisture supply to the Asian interior.
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Affiliation(s)
- Roderic Bosboom
- Palaeomagnetic Laboratory Fort Hoofddijk, Faculty of Geosciences, Utrecht University, Budapestlaan 17, 3584 CD Utrecht, The Netherlands
| | - Oleg Mandic
- Geological–Palaeontological Department, Natural History Museum Vienna, Burgring 7, A-1010 Wien, Austria
| | - Guillaume Dupont-Nivet
- Palaeomagnetic Laboratory Fort Hoofddijk, Faculty of Geosciences, Utrecht University, Budapestlaan 17, 3584 CD Utrecht, The Netherlands
- Géosciences Rennes, UMR 6118, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
- Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education (Peking University), 100871 Beijing, China
| | - Jean-Noël Proust
- Géosciences Rennes, UMR 6118, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
| | - Cholponbek Ormukov
- Institute of Seismology: Kyrgyz Republic Bishkek, Asanbay 52/1, 720060, Bishkek, Kyrgyzstan
| | - Jovid Aminov
- Institute of Geology, Earthquake Engineering and Seismology, 267 Ayni Street, 734053, Dushanbe, Tajikistan
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17
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Crame JA, Beu AG, Ineson JR, Francis JE, Whittle RJ, Bowman VC. The Early Origin of the Antarctic Marine Fauna and Its Evolutionary Implications. PLoS One 2014; 9:e114743. [PMID: 25493546 PMCID: PMC4262473 DOI: 10.1371/journal.pone.0114743] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 11/13/2014] [Indexed: 12/02/2022] Open
Abstract
The extensive Late Cretaceous – Early Paleogene sedimentary succession of Seymour Island, N.E. Antarctic Peninsula offers an unparalleled opportunity to examine the evolutionary origins of a modern polar marine fauna. Some 38 modern Southern Ocean molluscan genera (26 gastropods and 12 bivalves), representing approximately 18% of the total modern benthic molluscan fauna, can now be traced back through at least part of this sequence. As noted elsewhere in the world, the balance of the molluscan fauna changes sharply across the Cretaceous – Paleogene (K/Pg) boundary, with gastropods subsequently becoming more diverse than bivalves. A major reason for this is a significant radiation of the Neogastropoda, which today forms one of the most diverse clades in the sea. Buccinoidea is the dominant neogastropod superfamily in both the Paleocene Sobral Formation (SF) (56% of neogastropod genera) and Early - Middle Eocene La Meseta Formation (LMF) (47%), with the Conoidea (25%) being prominent for the first time in the latter. This radiation of Neogastropoda is linked to a significant pulse of global warming that reached at least 65°S, and terminates abruptly in the upper LMF in an extinction event that most likely heralds the onset of global cooling. It is also possible that the marked Early Paleogene expansion of neogastropods in Antarctica is in part due to a global increase in rates of origination following the K/Pg mass extinction event. The radiation of this and other clades at ∼65°S indicates that Antarctica was not necessarily an evolutionary refugium, or sink, in the Early – Middle Eocene. Evolutionary source – sink dynamics may have been significantly different between the Paleogene greenhouse and Neogene icehouse worlds.
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Affiliation(s)
- J. Alistair Crame
- British Antarctic Survey, Natural Environment Research Council, Cambridge, United Kingdom
- * E-mail:
| | | | - Jon R. Ineson
- Geological Survey of Denmark and Greenland, Copenhagen, Denmark
| | - Jane E. Francis
- British Antarctic Survey, Natural Environment Research Council, Cambridge, United Kingdom
| | - Rowan J. Whittle
- British Antarctic Survey, Natural Environment Research Council, Cambridge, United Kingdom
| | - Vanessa C. Bowman
- British Antarctic Survey, Natural Environment Research Council, Cambridge, United Kingdom
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18
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19
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Cramer BS, Miller KG, Barrett PJ, Wright JD. Late Cretaceous–Neogene trends in deep ocean temperature and continental ice volume: Reconciling records of benthic foraminiferal geochemistry (δ18O and Mg/Ca) with sea level history. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011jc007255] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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20
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Reisser CMO, Wood AR, Bell JJ, Gardner JPA. Connectivity, small islands and large distances: the Cellana strigilis limpet complex in the Southern Ocean. Mol Ecol 2011; 20:3399-413. [PMID: 21771140 DOI: 10.1111/j.1365-294x.2011.05185.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Southern Ocean contains some of the most isolated islands on Earth, and fundamental questions remain regarding their colonization and the connectivity of their coastal biotas. Here, we conduct a genetic investigation into the Cellana strigilis (limpet) complex that was originally classified based on morphological characters into six subspecies, five of which are endemic to the New Zealand (NZ) subantarctic and Chatham islands (44-52°S). Previous genetic analyses of C. strigilis from six of the seven island groups revealed two lineages with little or no within-lineage variation. We analysed C. strigilis samples from all seven island groups using two mitochondrial (COI and 16S), one nuclear (ATPase β) and 58 loci from four randomly amplified polymorphic DNA markers (RAPDs) and confirmed the existence of two distinct lineages. The pronounced genetic structuring within each lineage and the presence of private haplotypes in individual islands are the result of little genetic connectivity and therefore very high self-recruitment. This study supports the significance of the subantarctic islands as refugia during the last glacial maximum and adds to the knowledge of contemporary population connectivity among coastal populations of remote islands in large oceans and the distance barrier to gene flow that exists in the sea (despite its continuous medium) for most taxa.
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Affiliation(s)
- Céline M O Reisser
- Centre for Marine Environmental and Economic Research, School of Biological Sciences, Victoria University of Wellington, Wellington 6140, New Zealand.
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21
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Long L, Fang X, Miao Y, Bai Y, Wang Y. Northern Tibetan Plateau cooling and aridification linked to Cenozoic global cooling: Evidence from n-alkane distributions of Paleogene sedimentary sequences in the Xining Basin. CHINESE SCIENCE BULLETIN 2011. [DOI: 10.1007/s11434-011-4469-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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22
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Finnegan S, Bergmann K, Eiler JM, Jones DS, Fike DA, Eisenman I, Hughes NC, Tripati AK, Fischer WW. The magnitude and duration of Late Ordovician-Early Silurian glaciation. Science 2011; 331:903-6. [PMID: 21273448 DOI: 10.1126/science.1200803] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Understanding ancient climate changes is hampered by the inability to disentangle trends in ocean temperature from trends in continental ice volume. We used carbonate "clumped" isotope paleothermometry to constrain ocean temperatures, and thereby estimate ice volumes, through the Late Ordovician-Early Silurian glaciation. We find tropical ocean temperatures of 32° to 37°C except for short-lived cooling by ~5°C during the final Ordovician stage. Evidence for ice sheets spans much of the study interval, but the cooling pulse coincided with a glacial maximum during which ice volumes likely equaled or exceeded those of the last (Pleistocene) glacial maximum. This cooling also coincided with a large perturbation of the carbon cycle and the Late Ordovician mass extinction.
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Affiliation(s)
- Seth Finnegan
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
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23
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Deciphering and dating the red panda’s ancestry and early adaptive radiation of Musteloidea. Mol Phylogenet Evol 2009; 53:907-22. [DOI: 10.1016/j.ympev.2009.08.019] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 04/25/2009] [Accepted: 08/14/2009] [Indexed: 11/20/2022]
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Abstract
AbstractThe Infracambrian is a term for mostly Neoproterozoic successions in North Africa and areas to the east. Its base lies within the middle Neoproterozoic period, or Cryogenian, includes the youngest Neoproterozoic period, or Ediacaran, and continues into the early Cambrian to the level at which trilobites first appear. The Cryogenian lacks any biostratigraphic zonation; and no global biostratigraphic schemes exist for the Ediacaran. The formal classification of the Neoproterozoic is currently under review.The Cryogenian–Ediacaran (CE) interval includes at least three prominent diamictite horizons that are clearly linked to penecontemporaneous glaciations. The oldest is ‘Sturtian’, next oldest is ‘Marinoan’ (probably the most extensive), both names are Australian in origin but are used internationally. The Gaskiers glaciation is the youngest and probably the least extensive. There are important unresolved problems of the precise number, age, extent and nomenclature of the Neoproterozic glaciations in Australia.Several palaeomagnetic poles in the age range 600–550 Ma place glacial deposits of that age range in Australia in tropical latitudes. These data, together with older poles from Laurentia, gave rise to the notion of the Snowball Earth, in which the Earth froze over completely, but the profound refrigeration required appears to have had very little effect on biological evolution.Biostratigraphic zonation with the precision attainable throughout the Phanerozoic does not appear possible for the CE interval. Thus, most correlations are based on about 40 U–Pb and Re–Os dates. These confirm the existence of at least three glacial sequences (sequence is used here as an informal term), but it is possible that the Sturtian and Marinoan were essentially one glacial unit. Deglaciation was accompanied by the unique ‘cap carbonates’.The glacial sequences all show a characteristic δ13C pattern, but present knowledge is inadequate to use these patterns for detailed global correlation. The most reliable chemostratigraphic correlations are likely to be based on strontium isotope variations.Black shale horizons commonly follow deglaciation. A few basins produce Neoproterozoic hydrocarbons; others are potential producers. As a whole, the Neoproterozoic represents both a scientific and an exploration frontier.
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Affiliation(s)
- Alan G. Smith
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK (e-mail: )
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25
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Scheffer M, Bascompte J, Brock WA, Brovkin V, Carpenter SR, Dakos V, Held H, van Nes EH, Rietkerk M, Sugihara G. Early-warning signals for critical transitions. Nature 2009; 461:53-9. [PMID: 19727193 DOI: 10.1038/nature08227] [Citation(s) in RCA: 1486] [Impact Index Per Article: 99.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Complex dynamical systems, ranging from ecosystems to financial markets and the climate, can have tipping points at which a sudden shift to a contrasting dynamical regime may occur. Although predicting such critical points before they are reached is extremely difficult, work in different scientific fields is now suggesting the existence of generic early-warning signals that may indicate for a wide class of systems if a critical threshold is approaching.
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Affiliation(s)
- Marten Scheffer
- Department of Environmental Sciences, Wageningen University, PO Box 47, 6700 AA Wageningen, The Netherlands.
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Speelman EN, Van Kempen MML, Barke J, Brinkhuis H, Reichart GJ, Smolders AJP, Roelofs JGM, Sangiorgi F, de Leeuw JW, Lotter AF, Sinninghe Damsté JS. The Eocene Arctic Azolla bloom: environmental conditions, productivity and carbon drawdown. GEOBIOLOGY 2009; 7:155-70. [PMID: 19323694 DOI: 10.1111/j.1472-4669.2009.00195.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Enormous quantities of the free-floating freshwater fern Azolla grew and reproduced in situ in the Arctic Ocean during the middle Eocene, as was demonstrated by microscopic analysis of microlaminated sediments recovered from the Lomonosov Ridge during Integrated Ocean Drilling Program (IODP) Expedition 302. The timing of the Azolla phase (approximately 48.5 Ma) coincides with the earliest signs of onset of the transition from a greenhouse towards the modern icehouse Earth. The sustained growth of Azolla, currently ranking among the fastest growing plants on Earth, in a major anoxic oceanic basin may have contributed to decreasing atmospheric pCO2 levels via burial of Azolla-derived organic matter. The consequences of these enormous Azolla blooms for regional and global nutrient and carbon cycles are still largely unknown. Cultivation experiments have been set up to investigate the influence of elevated pCO2 on Azolla growth, showing a marked increase in Azolla productivity under elevated (760 and 1910 ppm) pCO2 conditions. The combined results of organic carbon, sulphur, nitrogen content and 15N and 13C measurements of sediments from the Azolla interval illustrate the potential contribution of nitrogen fixation in a euxinic stratified Eocene Arctic. Flux calculations were used to quantitatively reconstruct the potential storage of carbon (0.9-3.5 10(18) gC) in the Arctic during the Azolla interval. It is estimated that storing 0.9 10(18) to 3.5 10(18) g carbon would result in a 55 to 470 ppm drawdown of pCO2 under Eocene conditions, indicating that the Arctic Azolla blooms may have had a significant effect on global atmospheric pCO2 levels through enhanced burial of organic matter.
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Affiliation(s)
- E N Speelman
- Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands.
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27
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AUGÉ MARC, SMITH RICHARD. An assemblage of early Oligocene lizards (Squamata) from the locality of Boutersem (Belgium), with comments on the Eocene-Oligocene transition. Zool J Linn Soc 2009. [DOI: 10.1111/j.1096-3642.2008.00435.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Strugnell JM, Rogers AD, Prodöhl PA, Collins MA, Allcock AL. The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopuses. Cladistics 2008; 24:853-860. [DOI: 10.1111/j.1096-0031.2008.00234.x] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Abstract
In the Earth's history, periods of relatively stable climate have often been interrupted by sharp transitions to a contrasting state. One explanation for such events of abrupt change is that they happened when the earth system reached a critical tipping point. However, this remains hard to prove for events in the remote past, and it is even more difficult to predict if and when we might reach a tipping point for abrupt climate change in the future. Here, we analyze eight ancient abrupt climate shifts and show that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift. Such slowing down, measured as increased autocorrelation, can be mathematically shown to be a hallmark of tipping points. Therefore, our results imply independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds. Because the mechanism causing slowing down is fundamentally inherent to tipping points, it follows that our way to detect slowing down might be used as a universal early warning signal for upcoming catastrophic change. Because tipping points in ecosystems and other complex systems are notoriously hard to predict in other ways, this is a promising perspective.
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Late Eocene pollen records and palaeoenvironmental changes in northern Tibetan Plateau. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/s11430-008-0091-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Convey P, Gibson JAE, Hillenbrand CD, Hodgson DA, Pugh PJA, Smellie JL, Stevens MI. Antarctic terrestrial life – challenging the history of the frozen continent? Biol Rev Camb Philos Soc 2008; 83:103-17. [DOI: 10.1111/j.1469-185x.2008.00034.x] [Citation(s) in RCA: 247] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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32
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Eocene/Oligocene ocean de-acidification linked to Antarctic glaciation by sea-level fall. Nature 2008; 452:979-82. [DOI: 10.1038/nature06853] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Accepted: 02/19/2008] [Indexed: 11/09/2022]
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Pörtner HO, Peck L, Somero G. Thermal limits and adaptation in marine Antarctic ectotherms: an integrative view. Philos Trans R Soc Lond B Biol Sci 2008; 362:2233-58. [PMID: 17553776 PMCID: PMC2443174 DOI: 10.1098/rstb.2006.1947] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
A cause and effect understanding of thermal limitation and adaptation at various levels of biological organization is crucial in the elaboration of how the Antarctic climate has shaped the functional properties of extant Antarctic fauna. At the same time, this understanding requires an integrative view of how the various levels of biological organization may be intertwined. At all levels analysed, the functional specialization to permanently low temperatures implies reduced tolerance of high temperatures, as a trade-off. Maintenance of membrane fluidity, enzyme kinetic properties (Km and k(cat)) and protein structural flexibility in the cold supports metabolic flux and regulation as well as cellular functioning overall. Gene expression patterns and, even more so, loss of genetic information, especially for myoglobin (Mb) and haemoglobin (Hb) in notothenioid fishes, reflect the specialization of Antarctic organisms to a narrow range of low temperatures. The loss of Mb and Hb in icefish, together with enhanced lipid membrane densities (e.g. higher concentrations of mitochondria), becomes explicable by the exploitation of high oxygen solubility at low metabolic rates in the cold, where an enhanced fraction of oxygen supply occurs through diffusive oxygen flux. Conversely, limited oxygen supply to tissues upon warming is an early cause of functional limitation. Low standard metabolic rates may be linked to extreme stenothermy. The evolutionary forces causing low metabolic rates as a uniform character of life in Antarctic ectothermal animals may be linked to the requirement for high energetic efficiency as required to support higher organismic functioning in the cold. This requirement may result from partial compensation for the thermal limitation of growth, while other functions like hatching, development, reproduction and ageing are largely delayed. As a perspective, the integrative approach suggests that the patterns of oxygen- and capacity-limited thermal tolerance are linked, on one hand, with the capacity and design of molecules and membranes, and, on the other hand, with life-history consequences and lifestyles typically seen in the permanent cold. Future research needs to address the detailed aspects of these interrelationships.
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Affiliation(s)
- Hans O Pörtner
- Alfred-Wegener-Institut für Polar- und Meeresforschung, Physiologie mariner Tiere, 27515, Bremerhaven, Germany.
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Rogers AD. Evolution and biodiversity of Antarctic organisms: a molecular perspective. Philos Trans R Soc Lond B Biol Sci 2008; 362:2191-214. [PMID: 17553774 PMCID: PMC2443175 DOI: 10.1098/rstb.2006.1948] [Citation(s) in RCA: 151] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The Antarctic biota is highly endemic, and the diversity and abundance of taxonomic groups differ from elsewhere in the world. Such characteristics have resulted from evolution in isolation in an increasingly extreme environment over the last 100 Myr. Studies on Antarctic species represent some of the best examples of natural selection at the molecular, structural and physiological levels. Analyses of molecular genetics data are consistent with the diversity and distribution of marine and terrestrial taxa having been strongly influenced by geological and climatic cooling events over the last 70 Myr. Such events have resulted in vicariance driven by continental drift and thermal isolation of the Antarctic, and in pulses of species range contraction into refugia and subsequent expansion and secondary contact of genetically distinct populations or sister species during cycles of glaciation. Limited habitat availability has played a major role in structuring populations of species both in the past and in the present day. For these reasons, despite the apparent simplicity or homogeneity of Antarctic terrestrial and marine environments, populations of species are often geographically structured into genetically distinct lineages. In some cases, genetic studies have revealed that species defined by morphological characters are complexes of cryptic or sibling species. Climate change will cause changes in the distribution of many Antarctic and sub-Antarctic species through affecting population-level processes such as life history and dispersal.
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Cheng CHC, Detrich HW. Molecular ecophysiology of Antarctic notothenioid fishes. Philos Trans R Soc Lond B Biol Sci 2008; 362:2215-32. [PMID: 17553777 PMCID: PMC2443173 DOI: 10.1098/rstb.2006.1946] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The notothenioid fishes of the Southern Ocean surrounding Antarctica are remarkable examples of organismal adaptation to extreme cold. Their evolution since the mid-Miocene in geographical isolation and a chronically cold marine environment has resulted in extreme stenothermality of the extant species. Given the unique thermal history of the notothenioids, one may ask what traits have been gained, and conversely, what characters have been lost through change in the information content of their genomes. Two dramatic changes that epitomize such evolutionary transformations are the gain of novel antifreeze proteins, which are obligatory for survival in icy seawater, by most notothenioids and the paradoxical loss of respiratory haemoproteins and red blood cells, normally deemed indispensable for vertebrate life, by the species of a highly derived notothenioid family, the icefishes. Here, we review recent advances in our understanding of these traits and their evolution and suggest future avenues of investigation. The formerly coherent paradigm of notothenioid freeze avoidance, developed from three decades of study of antifreeze glycoprotein (AFGP) based cold adaptation, now faces challenges stemming from the recent discovery of antifreeze-deficient, yet freeze-resistant, early notothenioid life stages and from definitive evidence that the liver is not the physiological source of AFGPs in notothenioid blood. The resolution of these intriguing observations is likely to reveal new physiological traits that are unique to the notothenioids. Similarly, the model of AFGP gene evolution from a notothenioid pancreatic trypsinogen-like gene precursor is being expanded and refined based on genome-level analyses of the linked AFGP loci and their ancestral precursors. Finally, the application of comparative genomics to study evolutionary change in the AFGP genotypes of cool-temperate notothenioids from sub-Antarctic habitats, where these genes are not necessary, will contribute to the mechanistic understanding of the dynamics of AFGP gene gain and loss. In humans and most vertebrates, mutations in the alpha- or beta-globin genes or defects in globin chain synthesis are causes of severe genetic disease. Thus, the 16 species of haemoglobinless, erythrocyte-null icefishes are surprising anomalies -- in fact, they could only have evolved and thrived due to relaxed selection pressure for oxygen-binding proteins in the cold, oxygen-rich waters of the Southern Ocean. Fifteen of the sixteen icefish species have lost most of the adult alphabeta-globin locus and retain only a small 3' fragment of the alpha-globin gene. The only exception to this pattern occurs in Neopagetopsis ionah, which possesses a disrupted alphabeta-globin gene complex that probably represents a non-functional intermediate on the evolutionary pathway to near total globin gene extinction. By contrast, six of the icefish species fail to express myoglobin. The absence of myoglobin expression has occurred by several independent mutations and distinct mechanisms. Haemoprotein loss is correlated with dramatic increases in cellular mitochondrial density, heart size, blood volume and capillary bed volume. Evolution of these compensatory traits was probably facilitated by the homeostatic activity of nitric oxide, a key modulator of angiogenesis and mitochondrial biogenesis. These natural knockouts of the red blood cell lineage are an excellent genomic resource for erythroid gene discovery by comparative genomics, as illustrated for the newly described gene, bloodthirsty.
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Affiliation(s)
- C-H Christina Cheng
- Department of Animal Biology, University of Illinois, Urbana, IL 61801, USA.
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Aronson RB, Thatje S, Clarke A, Peck LS, Blake DB, Wilga CD, Seibel BA. Climate Change and Invasibility of the Antarctic Benthos. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2007. [DOI: 10.1146/annurev.ecolsys.38.091206.095525] [Citation(s) in RCA: 227] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Benthic communities living in shallow-shelf habitats in Antarctica (<100-m depth) are archaic in structure and function compared to shallow-water communities elsewhere. Modern predators, including fast-moving, durophagous (skeleton-crushing) bony fish, sharks, and crabs, are rare or absent; slow-moving invertebrates are generally the top predators; and epifaunal suspension feeders dominate many soft-substratum communities. Cooling temperatures beginning in the late Eocene excluded durophagous predators, ultimately resulting in the endemic living fauna and its unique food-web structure. Although the Southern Ocean is oceanographically isolated, the barriers to biological invasion are primarily physiological rather than geographic. Cold temperatures impose limits to performance that exclude modern predators. Global warming is now removing those physiological barriers, and crabs are reinvading Antarctica. As sea temperatures continue to rise, the invasion of durophagous predators will modernize the shelf benthos and erode the indigenous character of marine life in Antarctica.
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Affiliation(s)
| | - Sven Thatje
- National Oceanography Centre, Southampton, School of Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, United Kingdom
| | - Andrew Clarke
- British Antarctic Survey, NERC, Cambridge CB3 0ET, United Kingdom;,
| | - Lloyd S. Peck
- British Antarctic Survey, NERC, Cambridge CB3 0ET, United Kingdom;,
| | - Daniel B. Blake
- Department of Geology, University of Illinois, Urbana, Illinois 61801
| | - Cheryl D. Wilga
- Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island 02881;,
| | - Brad A. Seibel
- Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island 02881;,
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Stoeck T, Kasper J, Bunge J, Leslin C, Ilyin V, Epstein S. Protistan diversity in the Arctic: a case of paleoclimate shaping modern biodiversity? PLoS One 2007; 2:e728. [PMID: 17710128 PMCID: PMC1940325 DOI: 10.1371/journal.pone.0000728] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2007] [Accepted: 07/05/2007] [Indexed: 11/25/2022] Open
Abstract
Background The impact of climate on biodiversity is indisputable. Climate changes over geological time must have significantly influenced the evolution of biodiversity, ultimately leading to its present pattern. Here we consider the paleoclimate data record, inferring that present-day hot and cold environments should contain, respectively, the largest and the smallest diversity of ancestral lineages of microbial eukaryotes. Methodology/Principal Findings We investigate this hypothesis by analyzing an original dataset of 18S rRNA gene sequences from Western Greenland in the Arctic, and data from the existing literature on 18S rRNA gene diversity in hydrothermal vent, temperate sediments, and anoxic water column communities. Unexpectedly, the community from the cold environment emerged as one of the richest observed to date in protistan species, and most diverse in ancestral lineages. Conclusions/Significance This pattern is consistent with natural selection sweeps on aerobic non-psychrophilic microbial eukaryotes repeatedly caused by low temperatures and global anoxia of snowball Earth conditions. It implies that cold refuges persisted through the periods of greenhouse conditions, which agrees with some, although not all, current views on the extent of the past global cooling and warming events. We therefore identify cold environments as promising targets for microbial discovery.
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Affiliation(s)
- Thorsten Stoeck
- Department of Ecology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Jennifer Kasper
- Department of Ecology, University of Kaiserslautern, Kaiserslautern, Germany
| | - John Bunge
- Department of Statistical Science, Cornell University, Ithaca, New York, United States of America
| | - Chesley Leslin
- Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Valya Ilyin
- Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Slava Epstein
- Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
- Marine Science Center, Northeastern University, Nahant, Massachusetts, United States of America
- * To whom correspondence should be addressed. E-mail:
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Edgar KM, Wilson PA, Sexton PF, Suganuma Y. No extreme bipolar glaciation during the main Eocene calcite compensation shift. Nature 2007; 448:908-11. [PMID: 17713530 DOI: 10.1038/nature06053] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 06/28/2007] [Indexed: 11/08/2022]
Abstract
Major ice sheets were permanently established on Antarctica approximately 34 million years ago, close to the Eocene/Oligocene boundary, at the same time as a permanent deepening of the calcite compensation depth in the world's oceans. Until recently, it was thought that Northern Hemisphere glaciation began much later, between 11 and 5 million years ago. This view has been challenged, however, by records of ice rafting at high northern latitudes during the Eocene epoch and by estimates of global ice volume that exceed the storage capacity of Antarctica at the same time as a temporary deepening of the calcite compensation depth approximately 41.6 million years ago. Here we test the hypothesis that large ice sheets were present in both hemispheres approximately 41.6 million years ago using marine sediment records of oxygen and carbon isotope values and of calcium carbonate content from the equatorial Atlantic Ocean. These records allow, at most, an ice budget that can easily be accommodated on Antarctica, indicating that large ice sheets were not present in the Northern Hemisphere. The records also reveal a brief interval shortly before the temporary deepening of the calcite compensation depth during which the calcite compensation depth shoaled, ocean temperatures increased and carbon isotope values decreased in the equatorial Atlantic. The nature of these changes around 41.6 million years ago implies common links, in terms of carbon cycling, with events at the Eocene/Oligocene boundary and with the 'hyperthermals' of the Early Eocene climate optimum. Our findings help to resolve the apparent discrepancy between the geological records of Northern Hemisphere glaciation and model results that indicate that the threshold for continental glaciation was crossed earlier in the Southern Hemisphere than in the Northern Hemisphere.
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Affiliation(s)
- Kirsty M Edgar
- National Oceanography Centre, School of Ocean and Earth Science, European Way, Southampton, SO14 3ZH, UK
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Clarke JA, Ksepka DT, Stucchi M, Urbina M, Giannini N, Bertelli S, Narváez Y, Boyd CA. Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change. Proc Natl Acad Sci U S A 2007; 104:11545-50. [PMID: 17601778 PMCID: PMC1913862 DOI: 10.1073/pnas.0611099104] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2006] [Indexed: 11/18/2022] Open
Abstract
New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly it has been proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4-8 million years ago), well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes >30 million years earlier than prior data suggested, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude approximately 14 degrees S) regions during greenhouse earth conditions. One new species, Perudyptes devriesi, is among the deepest divergences within Sphenisciformes. The second, Icadyptes salasi, is the most complete giant (>1.5 m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper.
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Affiliation(s)
- Julia A Clarke
- Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Campus Box 8208, Raleigh, NC 27695, USA.
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Eldrett JS, Harding IC, Wilson PA, Butler E, Roberts AP. Continental ice in Greenland during the Eocene and Oligocene. Nature 2007; 446:176-9. [PMID: 17287724 DOI: 10.1038/nature05591] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2006] [Accepted: 01/08/2007] [Indexed: 11/09/2022]
Abstract
The Eocene and Oligocene epochs (approximately 55 to 23 million years ago) comprise a critical phase in Earth history. An array of geological records supported by climate modelling indicates a profound shift in global climate during this interval, from a state that was largely free of polar ice caps to one in which ice sheets on Antarctica approached their modern size. However, the early glaciation history of the Northern Hemisphere is a subject of controversy. Here we report stratigraphically extensive ice-rafted debris, including macroscopic dropstones, in late Eocene to early Oligocene sediments from the Norwegian-Greenland Sea that were deposited between about 38 and 30 million years ago. Our data indicate sediment rafting by glacial ice, rather than sea ice, and point to East Greenland as the likely source. Records of this type from one site alone cannot be used to determine the extent of ice involved. However, our data suggest the existence of (at least) isolated glaciers on Greenland about 20 million years earlier than previously documented, at a time when temperatures and atmospheric carbon dioxide concentrations were substantially higher.
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Affiliation(s)
- James S Eldrett
- School of Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, European Way, Southampton SO14 3ZH, UK
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Montañez IP, Tabor NJ, Niemeier D, Dimichele WA, Frank TD, Fielding CR, Isbell JL, Birgenheier LP, Rygel MC. CO2-Forced Climate and Vegetation Instability During Late Paleozoic Deglaciation. Science 2007; 315:87-91. [PMID: 17204648 DOI: 10.1126/science.1134207] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The late Paleozoic deglaciation is the vegetated Earth's only recorded icehouse-to-greenhouse transition, yet the climate dynamics remain enigmatic. By using the stable isotopic compositions of soil-formed minerals, fossil-plant matter, and shallow-water brachiopods, we estimated atmospheric partial pressure of carbon dioxide (pCO2) and tropical marine surface temperatures during this climate transition. Comparison to southern Gondwanan glacial records documents covariance between inferred shifts in pCO2, temperature, and ice volume consistent with greenhouse gas forcing of climate. Major restructuring of paleotropical flora in western Euramerica occurred in step with climate and pCO2 shifts, illustrating the biotic impact associated with past CO2-forced turnover to a permanent ice-free world.
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Affiliation(s)
- Isabel P Montañez
- Department of Geology, University of California, Davis, CA 95616, USA.
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Moran K, Backman J, Brinkhuis H, Clemens SC, Cronin T, Dickens GR, Eynaud F, Gattacceca J, Jakobsson M, Jordan RW, Kaminski M, King J, Koc N, Krylov A, Martinez N, Matthiessen J, McInroy D, Moore TC, Onodera J, O'Regan M, Pälike H, Rea B, Rio D, Sakamoto T, Smith DC, Stein R, St John K, Suto I, Suzuki N, Takahashi K, Watanabe M, Yamamoto M, Farrell J, Frank M, Kubik P, Jokat W, Kristoffersen Y. The Cenozoic palaeoenvironment of the Arctic Ocean. Nature 2006; 441:601-5. [PMID: 16738653 DOI: 10.1038/nature04800] [Citation(s) in RCA: 404] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Accepted: 04/13/2006] [Indexed: 11/08/2022]
Abstract
The history of the Arctic Ocean during the Cenozoic era (0-65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm 'greenhouse' world, during the late Palaeocene and early Eocene epochs, to a colder 'icehouse' world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent approximately 14 Myr, we find sedimentation rates of 1-2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (approximately 3.2 Myr ago) and East Antarctic ice (approximately 14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (approximately 45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at approximately 49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (approximately 55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change.
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Affiliation(s)
- Kathryn Moran
- Graduate School of Oceanography & Department of Ocean Engineering, University of Rhode Island, Narragansett, Rhode Island 02882, USA.
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Li F, Wu N, Rousseau DD. Preliminary study of mollusk fossils in the Qinan Miocene loess-soil sequence in western Chinese Loess Plateau. ACTA ACUST UNITED AC 2006. [DOI: 10.1007/s11430-006-0724-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
Age estimates for the opening of Drake Passage range from 49 to 17 million years ago (Ma), complicating interpretations of the relationship between ocean circulation and global cooling. Secular variations of neodymium isotope ratios at Agulhas Ridge (Southern Ocean, Atlantic sector) suggest an influx of shallow Pacific seawater approximately 41 Ma. The timing of this connection and the subsequent deepening of the passage coincide with increased biological productivity and abrupt climate reversals. Circulation/productivity linkages are proposed as a mechanism for declining atmospheric carbon dioxide. These results also indicate that Drake Passage opened before the Tasmanian Gateway, implying the late Eocene establishment of a complete circum-Antarctic pathway.
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Affiliation(s)
- Howie D Scher
- Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USA.
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