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Li QQ, Khasbagan, Zhang ZP, Wen J, Yu Y. Plastid phylogenomics of the tribe potentilleae (Rosaceae). Mol Phylogenet Evol 2024; 190:107961. [PMID: 37918684 DOI: 10.1016/j.ympev.2023.107961] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 04/08/2023] [Accepted: 10/30/2023] [Indexed: 11/04/2023]
Abstract
The tribe Potentilleae comprises approximately 1700 species in 13 genera, making it one of the largest of the 16 tribes in Rosaceae. Our understanding of the composition and relationships among members of Potentilleae has advanced dramatically with the application of molecular markers in the last two decades. Yet there is still much work remaining toward a robust phylogenetic framework for the entire Potentilleae and a comprehensive genus-level dating framework for the tribe. The goals of the present study were to establish a phylogenetic framework for Potentilleae, infer the origin and diversification of the tribe using a temporal framework, and explore the taxonomic implications in light of the updated phylogenetic framework. We used the plastome sequences from 158 accessions representing 139 taxa covering all 13 recognized genera of the tribe to reconstruct the Potentilleae phylogeny. High phylogenetic resolution was recovered along the Potentilleae backbone. Two major clades were recovered within Potentilleae, corresponding to the two subtribes Fragariinae and Potentillinae. Within Fragariinae, two subclades were recovered. In one subclade, Sibbaldia sensu stricto is sister to a clade containing Sibbaldianthe, Comarum, Farinopsis, and Alchemilla sensu lato. In the other subclade, Fragaria is sister to a clade comprising Chamaerhodos, Chamaecallis, Drymocallis, Dasiphora, and Potaninia. Within Potentillinae, Argentina is sister to Potentilla sensu stricto. Within Potentilla sensu stricto, clade Himalaya is sister to Alba, and the Himalaya-Alba clade together is sister to a clade comprising Reptans, Potentilla ancistrifolia Bunge, Fragarioides, Ivesioid, and Argentea. Divergence time estimates indicated that tribe Potentilleae originated during the middle Eocene, and subtribes Fragariinae and Potentillinae diverged around the Eocene-Oligocene transition, and divergence times dated for Potentilleae genera ranged from the early Miocene to the late Pleistocene.
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Affiliation(s)
- Qin-Qin Li
- College of Life Science and Technology, Inner Mongolia Normal University, Hohhot 010022, Inner Mongolia, China; Department of Botany, National Museum of Natural History, Smithsonian Institution, PO Box 37012, Washington, DC 20013-7012, USA
| | - Khasbagan
- College of Life Science and Technology, Inner Mongolia Normal University, Hohhot 010022, Inner Mongolia, China
| | - Zhi-Ping Zhang
- College of Computer Science and Technology, Inner Mongolia Normal University, Hohhot 010022, Inner Mongolia, China
| | - Jun Wen
- Department of Botany, National Museum of Natural History, Smithsonian Institution, PO Box 37012, Washington, DC 20013-7012, USA.
| | - Yan Yu
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China.
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Paleoceanographic Perturbations and the Marine Carbonate System during the Middle to Late Miocene Carbonate Crash—A Critical Review. GEOSCIENCES 2021. [DOI: 10.3390/geosciences11020094] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study intends to review and assess the middle to late Miocene Carbonate Crash (CC) events in the low to mid latitudes of the Pacific, Indian, Caribbean and Atlantic Oceans as part of the global paleoceanographic reorganisations between 12 and 9 Ma with an emphasis on record preservation and their relation to mass accumulation rates (MAR). In the Eastern Pacific the accumulation changes in carbonate and opal probably reflect an El-Niño-like state of low productivity, which marks the beginning of the CC-event (11.5 Ma), followed by decreased preservation and influx of corrosive bottom waters (10.3 to 10.1 Ma). At the same time in the Atlantic, carbonate preservation considerably increases, suggesting basin-to-basin fractionation. The low-latitude Indian Ocean, the Pacific and the Caribbean are all characterised by a similar timing of preservation increase starting at ~9.6–9.4 Ma, while their MARs show drastic changes with different timing of events. The Atlantic preservation pattern shows an increase as early as 11.5 Ma and becomes even better after 10.1 Ma. The shallow Indian Ocean (Mascarene plateau) is characterised by low carbonate accumulation throughout and increasing preservation after 9.4 Ma. At the same time, the preservation in the Atlantic, including the Caribbean, is increasing due to enhanced North Atlantic deep-water formation, leading to the increase in carbonate accumulation at 10 Ma. Moreover, the shoaling of the Central American Isthmus might have helped to enhance Caribbean preservation after 9.4 Ma. Lower nannoplankton productivity in the Atlantic should have additionally contributed to low mass accumulation rates during the late CC-interval. Overall, it can be inferred that these carbonate minima events during the Miocene may be the result of decreased surface ocean productivity and oceanographically driven increased seafloor dissolution.
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Neville LA, Grasby SE, McNeil DH. Limited freshwater cap in the Eocene Arctic Ocean. Sci Rep 2019; 9:4226. [PMID: 30862936 PMCID: PMC6414537 DOI: 10.1038/s41598-019-40591-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 02/04/2019] [Indexed: 11/19/2022] Open
Abstract
Remains of the freshwater fern Azolla, found in Eocene (~50 Ma ago) sediments in the modern central Arctic Ocean, have been used to suggest that seasonal freshwater caps covered the entire Arctic Ocean during that time, with significant impact on global ocean circulation and climate. However, these records are located on the Lomonosov Ridge, which during the Eocene was a continental fragment barely rifted from Eurasia, separating the smaller Eurasian Basin from the much larger Amerasian Basin to the west. As such, the Lomonosov Ridge does not necessarily record environmental conditions of the broader Arctic Ocean. We tested the hypothesis of freshwater caps by examining sediment records from the western Amerasian Basin. Here we show that in the larger Amerasian Basin the Azolla event is associated with marine microfauna along with allochthonous (terrestrially sourced) organic matter. We propose that Azolla events are related to an increased hydrologic cycle washing terrestrially sourced Azolla, and other organics, into the Arctic Ocean. If freshwater caps did occur, then they were at best restricted to the small Eurasian Basin and would have had a limited impact on Eocene global climate, contrary to current models.
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Affiliation(s)
- Lisa A Neville
- Geological Survey of Canada, Natural Resources Canada, Calgary, Alberta, T2L 2A7, Canada.,AGAT Laboratories, Calgary, Alberta, T2E 7J2, Canada
| | - Stephen E Grasby
- Geological Survey of Canada, Natural Resources Canada, Calgary, Alberta, T2L 2A7, Canada.
| | - David H McNeil
- Geological Survey of Canada, Natural Resources Canada, Calgary, Alberta, T2L 2A7, Canada
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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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Stärz M, Jokat W, Knorr G, Lohmann G. Threshold in North Atlantic-Arctic Ocean circulation controlled by the subsidence of the Greenland-Scotland Ridge. Nat Commun 2017; 8:15681. [PMID: 28580952 PMCID: PMC5465373 DOI: 10.1038/ncomms15681] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Accepted: 04/19/2017] [Indexed: 11/30/2022] Open
Abstract
High latitude ocean gateway changes are thought to play a key role in Cenozoic climate evolution. However, the underlying ocean dynamics are poorly understood. Here we use a fully coupled atmosphere-ocean model to investigate the effect of ocean gateway formation that is associated with the subsidence of the Greenland–Scotland Ridge. We find a threshold in sill depth (∼50 m) that is linked to the influence of wind mixing. Sill depth changes within the wind mixed layer establish lagoonal and estuarine conditions with limited exchange across the sill resulting in brackish or even fresher Arctic conditions. Close to the threshold the ocean regime is highly sensitive to changes in atmospheric CO2 and the associated modulation in the hydrological cycle. For larger sill depths a bi-directional flow regime across the ridge develops, providing a baseline for the final step towards the establishment of a modern prototype North Atlantic-Arctic water exchange. During the Cenozoic the Arctic Ocean change from a restricted freshwater regime towards more saline modern ocean conditions is supposedly driven by the subsidence of the Greenland-Scotland Ridge. Here, the authors derive a threshold for this shift, constrained by the characteristic depth of wind mixing.
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Affiliation(s)
- Michael Stärz
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany
| | - Wilfried Jokat
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany
| | - Gregor Knorr
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany
| | - Gerrit Lohmann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany
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Stein R, Fahl K, Schreck M, Knorr G, Niessen F, Forwick M, Gebhardt C, Jensen L, Kaminski M, Kopf A, Matthiessen J, Jokat W, Lohmann G. Evidence for ice-free summers in the late Miocene central Arctic Ocean. Nat Commun 2016; 7:11148. [PMID: 27041737 PMCID: PMC4822014 DOI: 10.1038/ncomms11148] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 02/24/2016] [Indexed: 11/10/2022] Open
Abstract
Although the permanently to seasonally ice-covered Arctic Ocean is a unique and sensitive component in the Earth's climate system, the knowledge of its long-term climate history remains very limited due to the restricted number of pre-Quaternary sedimentary records. During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides along Lomonosov Ridge. Removal of younger sediments from steep headwalls has led to exhumation of Miocene sediments close to the seafloor. Here we document the presence of IP25 as a proxy for spring sea-ice cover and alkenone-based summer sea-surface temperatures >4 °C that support a seasonal sea-ice cover with an ice-free summer season being predominant during the late Miocene in the central Arctic Ocean. A comparison of our proxy data with Miocene climate simulations seems to favour either relatively high late Miocene atmospheric CO2 concentrations and/or a weak sensitivity of the model to simulate the magnitude of high-latitude warming in a warmer than modern climate.
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Affiliation(s)
- Ruediger Stein
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany.,Department of Geosciences (FB5), University of Bremen, Klagenfurter Strasse 4, Bremen 28359, Germany
| | - Kirsten Fahl
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany
| | - Michael Schreck
- Arctic Research Centre, Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 406-840, Korea
| | - Gregor Knorr
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany
| | - Frank Niessen
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany
| | - Matthias Forwick
- Institute of Geology, University of Tromsø-The Arctic University of Norway, P O Box 6050 Langnes, Tromsø 9037, Norway
| | - Catalina Gebhardt
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany
| | - Laura Jensen
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany
| | - Michael Kaminski
- Geosciences Department, College of Petroleum Engineering &Geosciences, King Fahd University of Petroleum &Minerals, Dhahran 31261, Saudi Arabia
| | - Achim Kopf
- Department of Geosciences (FB5), University of Bremen, Klagenfurter Strasse 4, Bremen 28359, Germany.,MARUM-Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, Bremen 28359, Germany
| | - Jens Matthiessen
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany
| | - Wilfried Jokat
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany.,Department of Geosciences (FB5), University of Bremen, Klagenfurter Strasse 4, Bremen 28359, Germany
| | - Gerrit Lohmann
- Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, Bremerhaven 27568, Germany.,MARUM-Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, Bremen 28359, Germany
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Veith M, Göçmen B, Sotiropoulos K, Kieren S, Godmann O, Steinfartz S. Seven at one blow: the origin of major lineages of the viviparous Lycian salamanders (Lyciasalamandra Veith and Steinfartz, 2004) was triggered by a single paleo-historic event. AMPHIBIA-REPTILIA 2016. [DOI: 10.1163/15685381-00003067] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The number of tectonic and climatic events that are used to explain speciation processes in the eastern Mediterranean region is low compared to the western Mediterranean. Among them, the emergence of the mid-Aegean trench and the Messinian Salinity Crisis (MSC) often concurred with speciation time estimates that were inferred from molecular data. We here present a dated molecular phylogeny of Lyciasalamandra from Turkey and Greece based on ca. 4500 bp of the mitochondrial genome (3000 bp of three nuclear genes appeared to be completely inconclusive due to their extremely low degree of variation among taxa). Seven major lineages emerged simultaneously from a basal hard polytomy. A scenario that dates this polytomy to 12.3 and 10.2 million years ago, around the final emergence of the mid-Aegean trench, appears to be most plausible. The MSC can be made responsible for first intraspecific divergence events within L. luschani, L. fazilae and L. flavimembris. Further diversification can be explained by Pliocene and Pleistocene glaciations. Based on levels of molecular differentiation we suggest the recently described species L. arikani, L. irfani and L. yehudahi to be treated as subspecies of L. billae.
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Affiliation(s)
- Michael Veith
- Department of Biogeography, Trier University, Universitätsring 15, 54296 Trier, Germany
| | - Bayram Göçmen
- Zoology Section, Department of Biology, Faculty of Science, Ege University, 35100 Bornova, İzmir, Turkey
| | - Konstantinos Sotiropoulos
- Department of Biological Applications & Technologies, University of Ioannina, 45110 Ioannina, Greece
| | - Sarah Kieren
- Department of Biogeography, Trier University, Universitätsring 15, 54296 Trier, Germany
| | | | - Sebastian Steinfartz
- Zoological Institute, Technische Universität Braunschweig, Mendelssohnstraße 4, 38106 Braunschweig, Germany
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10
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Tremblay LB, Schmidt GA, Pfirman S, Newton R, DeRepentigny P. Is ice-rafted sediment in a North Pole marine record evidence for perennial sea-ice cover? PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2015; 373:rsta.2014.0168. [PMID: 26347534 DOI: 10.1098/rsta.2014.0168] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/29/2015] [Indexed: 06/05/2023]
Abstract
Ice-rafted sediments of Eurasian and North American origin are found consistently in the upper part (13 Ma BP to present) of the Arctic Coring Expedition (ACEX) ocean core from the Lomonosov Ridge, near the North Pole (≈88° N). Based on modern sea-ice drift trajectories and speeds, this has been taken as evidence of the presence of a perennial sea-ice cover in the Arctic Ocean from the middle Miocene onwards (Krylov et al. 2008 Paleoceanography 23, PA1S06. (doi:10.1029/2007PA001497); Darby 2008 Paleoceanography 23, PA1S07. (doi:10.1029/2007PA001479)). However, other high latitude land and marine records indicate a long-term trend towards cooling broken by periods of extensive warming suggestive of a seasonally ice-free Arctic between the Miocene and the present (Polyak et al. 2010 Quaternary Science Reviews 29, 1757-1778. (doi:10.1016/j.quascirev.2010.02.010)). We use a coupled sea-ice slab-ocean model including sediment transport tracers to map the spatial distribution of ice-rafted deposits in the Arctic Ocean. We use 6 hourly wind forcing and surface heat fluxes for two different climates: one with a perennial sea-ice cover similar to that of the present day and one with seasonally ice-free conditions, similar to that simulated in future projections. Model results confirm that in the present-day climate, sea ice takes more than 1 year to transport sediment from all its peripheral seas to the North Pole. However, in a warmer climate, sea-ice speeds are significantly faster (for the same wind forcing) and can deposit sediments of Laptev, East Siberian and perhaps also Beaufort Sea origin at the North Pole. This is primarily because of the fact that sea-ice interactions are much weaker with a thinner ice cover and there is less resistance to drift. We conclude that the presence of ice-rafted sediment of Eurasian and North American origin at the North Pole does not imply a perennial sea-ice cover in the Arctic Ocean, reconciling the ACEX ocean core data with other land and marine records.
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Affiliation(s)
- L B Tremblay
- Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, Canada H3A OB9 Lamont-Doherty Earth Observatory of Columbia University, 61 route 9W, Palisades, NY 10964, USA
| | - G A Schmidt
- NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
| | - S Pfirman
- Barnard College, 3009 Broadway, New York, NY 10027, USA
| | - R Newton
- Lamont-Doherty Earth Observatory of Columbia University, 61 route 9W, Palisades, NY 10964, USA
| | - P DeRepentigny
- Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, Canada H3A OB9
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Pointing SB, Burkhard Büdel, Convey P, Gillman LN, Körner C, Leuzinger S, Vincent WF. Biogeography of photoautotrophs in the high polar biome. FRONTIERS IN PLANT SCIENCE 2015; 6:692. [PMID: 26442009 PMCID: PMC4566839 DOI: 10.3389/fpls.2015.00692] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 08/21/2015] [Indexed: 11/19/2023]
Abstract
The global latitudinal gradient in biodiversity weakens in the high polar biome and so an alternative explanation for distribution of Arctic and Antarctic photoautotrophs is required. Here we identify how temporal, microclimate and evolutionary drivers of biogeography are important, rather than the macroclimate features that drive plant diversity patterns elsewhere. High polar ecosystems are biologically unique, with a more central role for bryophytes, lichens and microbial photoautotrophs over that of vascular plants. Constraints on vascular plants arise mainly due to stature and ontogenetic barriers. Conversely non-vascular plant and microbial photoautotroph distribution is correlated with favorable microclimates and the capacity for poikilohydric dormancy. Contemporary distribution also depends on evolutionary history, with adaptive and dispersal traits as well as legacy influencing biogeography. We highlight the relevance of these findings to predicting future impacts on diversity of polar photoautotrophs and to the current status of plants in Arctic and Antarctic conservation policy frameworks.
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Affiliation(s)
- Stephen B. Pointing
- Institute for Applied Ecology New Zealand, School of Applied Sciences, Auckland University of Technology, Auckland, New Zealand
| | - Burkhard Büdel
- Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Peter Convey
- British Antarctic Survey, NERC, Cambridge, UK
- National Antarctic Research Centre, University of Malaya, Kuala Lumpur, Malaysia
| | - Len N. Gillman
- Institute for Applied Ecology New Zealand, School of Applied Sciences, Auckland University of Technology, Auckland, New Zealand
| | | | - Sebastian Leuzinger
- Institute for Applied Ecology New Zealand, School of Applied Sciences, Auckland University of Technology, Auckland, New Zealand
| | - Warwick F. Vincent
- Centre d’\Études Nordiques and Département de Biologie, Université Laval, Québec, QC, Canada
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Manzetti S. Remediation technologies for oil-drilling activities in the Arctic: oil-spill containment and remediation in open water. ACTA ACUST UNITED AC 2014. [DOI: 10.1080/21622515.2014.966156] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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13
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Miller RM. Evidence for the evolution of the Kalahari dunes from the Auob River, southeastern Namibia. ACTA ACUST UNITED AC 2014. [DOI: 10.1080/0035919x.2014.955555] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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14
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Evolution and biogeography of gymnosperms. Mol Phylogenet Evol 2014; 75:24-40. [DOI: 10.1016/j.ympev.2014.02.005] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 02/06/2014] [Accepted: 02/10/2014] [Indexed: 11/20/2022]
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15
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First record of eocene bony fishes and crocodyliforms from Canada's Western Arctic. PLoS One 2014; 9:e96079. [PMID: 24788829 PMCID: PMC4006887 DOI: 10.1371/journal.pone.0096079] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 04/03/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Discovery of Eocene non-marine vertebrates, including crocodylians, turtles, bony fishes, and mammals in Canada's High Arctic was a critical paleontological contribution of the last century because it indicated that this region of the Arctic had been mild, temperate, and ice-free during the early - middle Eocene (∼53-50 Ma), despite being well above the Arctic Circle. To date, these discoveries have been restricted to Canada's easternmost Arctic - Ellesmere and Axel Heiberg Islands (Nunavut). Although temporally correlative strata crop out over 1,000 km west, on Canada's westernmost Arctic Island - Banks Island, Northwest Territories - they have been interpreted as predominantly marine. We document the first Eocene bony fish and crocodyliform fossils from Banks Island. PRINCIPAL FINDINGS We describe fossils of bony fishes, including lepisosteid (Atractosteus), esocid (pike), and amiid, and a crocodyliform, from lower - middle Eocene strata of the Cyclic Member, Eureka Sound Formation within Aulavik National Park (∼76°N. paleolat.). Palynology suggests the sediments are late early to middle Eocene in age, and likely spanned the Early Eocene Climatic Optimum (EECO). CONCLUSIONS/SIGNIFICANCE These fossils extend the geographic range of Eocene Arctic lepisosteids, esocids, amiids, and crocodyliforms west by approximately 40° of longitude or ∼1100 km. The low diversity bony fish fauna, at least at the family level, is essentially identical on Ellesmere and Banks Islands, suggesting a pan-High Arctic bony fish fauna of relatively basal groups around the margin of the Eocene Arctic Ocean. From a paleoclimatic perspective, presence of a crocodyliform, gar and amiid fishes on northern Banks provides further evidence that mild, year-round temperatures extended across the Canadian Arctic during early - middle Eocene time. Additionally, the Banks Island crocodyliform is consistent with the phylogenetic hypothesis of a Paleogene divergence time between the two extant alligatorid lineages Alligator mississippiensis and A. sinensis, and high-latitude dispersal across Beringia.
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De Schepper S, Groeneveld J, Naafs BDA, Van Renterghem C, Hennissen J, Head MJ, Louwye S, Fabian K. Northern hemisphere glaciation during the globally warm early Late Pliocene. PLoS One 2013; 8:e81508. [PMID: 24349081 PMCID: PMC3861316 DOI: 10.1371/journal.pone.0081508] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 10/14/2013] [Indexed: 11/19/2022] Open
Abstract
The early Late Pliocene (3.6 to ∼3.0 million years ago) is the last extended interval in Earth's history when atmospheric CO2 concentrations were comparable to today's and global climate was warmer. Yet a severe global glaciation during marine isotope stage (MIS) M2 interrupted this phase of global warmth ∼3.30 million years ago, and is seen as a premature attempt of the climate system to establish an ice-age world. Here we propose a conceptual model for the glaciation and deglaciation of MIS M2 based on geochemical and palynological records from five marine sediment cores along a Caribbean to eastern North Atlantic transect. Our records show that increased Pacific-to-Atlantic flow via the Central American Seaway weakened the North Atlantic Current and attendant northward heat transport prior to MIS M2. The consequent cooling of the northern high latitude oceans permitted expansion of the continental ice sheets during MIS M2, despite near-modern atmospheric CO2 concentrations. Sea level drop during this glaciation halted the inflow of Pacific water to the Atlantic via the Central American Seaway, allowing the build-up of a Caribbean Warm Pool. Once this warm pool was large enough, the Gulf Stream-North Atlantic Current system was reinvigorated, leading to significant northward heat transport that terminated the glaciation. Before and after MIS M2, heat transport via the North Atlantic Current was crucial in maintaining warm climates comparable to those predicted for the end of this century.
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Affiliation(s)
- Stijn De Schepper
- Department of Earth Science, University of Bergen, Bergen, Norway
- Geosciences Department, University of Bremen, Bremen, Germany
- * E-mail:
| | - Jeroen Groeneveld
- MARUM – Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - B. David A Naafs
- Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
| | | | - Jan Hennissen
- Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Martin J. Head
- Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
- Department of Earth Sciences, Brock University, St. Catharines, Ontario, Canada
| | - Stephen Louwye
- Research Unit Palaeontology, Ghent University, Ghent, Belgium
| | - Karl Fabian
- Norwegian Geological Survey, Trondheim, Norway
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Haywood AM, Dolan AM, Pickering SJ, Dowsett HJ, McClymont EL, Prescott CL, Salzmann U, Hill DJ, Hunter SJ, Lunt DJ, Pope JO, Valdes PJ. On the identification of a Pliocene time slice for data-model comparison. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20120515. [PMID: 24043865 PMCID: PMC3785814 DOI: 10.1098/rsta.2012.0515] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The characteristics of the mid-Pliocene warm period (mPWP: 3.264-3.025 Ma BP) have been examined using geological proxies and climate models. While there is agreement between models and data, details of regional climate differ. Uncertainties in prescribed forcings and in proxy data limit the utility of the interval to understand the dynamics of a warmer than present climate or evaluate models. This uncertainty comes, in part, from the reconstruction of a time slab rather than a time slice, where forcings required by climate models can be more adequately constrained. Here, we describe the rationale and approach for identifying a time slice(s) for Pliocene environmental reconstruction. A time slice centred on 3.205 Ma BP (3.204-3.207 Ma BP) has been identified as a priority for investigation. It is a warm interval characterized by a negative benthic oxygen isotope excursion (0.21-0.23‰) centred on marine isotope stage KM5c (KM5.3). It occurred during a period of orbital forcing that was very similar to present day. Climate model simulations indicate that proxy temperature estimates are unlikely to be significantly affected by orbital forcing for at least a precession cycle centred on the time slice, with the North Atlantic potentially being an important exception.
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Affiliation(s)
- Alan M. Haywood
- School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
| | - Aisling M. Dolan
- School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
| | - Steven J. Pickering
- School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
| | - Harry J. Dowsett
- Eastern Geology and Paleoclimate Science Center, USGS, 926A National Center, Reston, VA 20192, USA
| | - Erin L. McClymont
- Department of Geography, Durham University, South Road, Durham DH1 3LE, UK
| | - Caroline L. Prescott
- School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
| | - Ulrich Salzmann
- School of Built and Natural Environment, Northumbria University, Ellison Building, Newcastle upon Tyne NE1 8ST, UK
| | - Daniel J. Hill
- School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
- British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK
| | - Stephen J. Hunter
- School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
| | - Daniel J. Lunt
- School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK
| | - James O. Pope
- School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
| | - Paul J. Valdes
- School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK
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Kuklinski P, Taylor PD, Denisenko NV, Berning B. Atlantic origin of the arctic biota? Evidence from phylogenetic and biogeographical analysis of the cheilostome bryozoan genus pseudoflustra. PLoS One 2013; 8:e59152. [PMID: 23536863 PMCID: PMC3607580 DOI: 10.1371/journal.pone.0059152] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 02/12/2013] [Indexed: 11/19/2022] Open
Abstract
The intricate geological evolution of the Arctic Ocean is paralleled by complexities in the biogeographical and phylogenetical histories of the Arctic biota, including bryozoans. Here we present revised taxonomic descriptions for all known species of the bryozoan genus Pseudoflustra, and use the present-day distributions and phylogenetic relationships between these species to infer the historical biogeography of the genus. Nine species belonging to the genus Pseudoflustra are recognized in the Arctic and North Atlantic. One new species, previously identified as Ichthyaria aviculata, is described as Pseudoflustra radeki sp. nov. Another species, previously assigned to Smittoidea as S. perrieri, is transferred to Pseudoflustra. Biogeographical analysis of Pseudoflustra reveals that species distributions mostly match current patterns pertaining in the North Atlantic and Arctic Ocean. Distributions were probably shaped by recent geological history as present-day current directions in the Arctic Ocean are believed to have been similar for at least the last 120 000 years. Phylogenetic analysis of Pseudoflustra places the five Arctic-North Atlantic species in a clade crownward of a paraphyletic grouping of North Atlantic species. Given that the Arctic Ocean was fully glaciated until 18 000 years, the most likely explanation for this phylogeographical pattern is that species of Pseudoflustra colonized the Arctic relatively recently from North Atlantic sources. However, a fuller understanding of the origin of Pseudoflustra in the Arctic will require molecular and fossil data, neither of which are currently available.
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Affiliation(s)
- Piotr Kuklinski
- Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland ; Natural History Museum, London, United Kingdom.
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Hoffmann MH, Schneider J, Hase P, Röser M. Rapid and recent world-wide diversification of bluegrasses (Poa, Poaceae) and related genera. PLoS One 2013; 8:e60061. [PMID: 23544123 PMCID: PMC3609727 DOI: 10.1371/journal.pone.0060061] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 02/25/2013] [Indexed: 11/19/2022] Open
Abstract
Rapid species diversifications provide fascinating insight into the development of biodiversity in time and space. Most biological radiations studied to date, for example that of cichlid fishes or Andean lupines, are confined to isolated geographical areas like lakes, islands or island-like regions. Using DNA sequence data of the ribosomal internal transcribed spacer (ITS) for many species of the Poa alliance, a group comprising about 775 C3 grass species, revealed rapid and parallel diversifications in various parts of the world. Some of these radiations are restricted to isolated areas like the Andes, whereas others are typical of the lowlands of mainly the northern hemisphere. These radiations thus are not restricted to island-like areas and are seemingly actively ongoing. The ages of the diversifying clades are estimated to be 2.5–0.23 million years (Myr). Conservative diversification rates in the Poa alliance amount to 0.89–3.14 species per Myr, thus are in the order of, or even exceeding, other instances of well-known radiations. The grass radiations of the mainly cold-adapted Poa alliance coincide with the Late Tertiary global cooling, which resulted in the retreat of forests and the subsequent formation of cold-adapted grasslands especially in the northern, but also in parts of the southern hemisphere. The cold tolerance, suggested to be one of the ecological key innovations, may have been acquired during the early diversification of the subfamily Pooideae, but became significant millions of years later during the Pliocene/Pleistocene radiation of the Poa alliance.
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Affiliation(s)
- Matthias H Hoffmann
- Martin Luther University Halle-Wittenberg, Institute of Biology, Geobotany and Botanical Garden, Halle, Germany.
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20
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Abstract
Fundamental differences in the distribution of oceans and landmasses in the Northern and Southern Hemispheres potentially impact patterns of biological diversity in the two areas. The evolutionary history of conifers provides an opportunity to explore these dynamics, because the majority of extant conifer species belong to lineages that have been broadly confined to the Northern or Southern Hemisphere during the Cenozoic. Incorporating genetic information with a critical review of fossil evidence, we developed an age-calibrated phylogeny sampling ∼80% of living conifer species. Most extant conifer species diverged recently during the Neogene within clades that generally were established during the later Mesozoic, but lineages that diversified mainly in the Southern Hemisphere show a significantly older distribution of divergence ages than their counterparts in the Northern Hemisphere. Our tree topology and divergence times also are best fit by diversification models in which Northern Hemisphere conifer lineages have higher rates of species turnover than Southern Hemisphere lineages. The abundance of recent divergences in northern clades may reflect complex patterns of migration and range shifts during climatic cycles over the later Neogene leading to elevated rates of speciation and extinction, whereas the scattered persistence of mild, wetter habitats in the Southern Hemisphere may have favored the survival of older lineages.
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Convey P, Aitken S, di Prisco G, Gill M, Coulson S, Barry T, Jónsdóttir I, Dang P, Hik D, Kulkarni T, Lewis G. The impacts of climate change on circumpolar biodiversity. ACTA ACUST UNITED AC 2012. [DOI: 10.1080/14888386.2012.732556] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Ishitani Y, Ujiié Y, de Vargas C, Not F, Takahashi K. Phylogenetic relationships and evolutionary patterns of the order Collodaria (Radiolaria). PLoS One 2012; 7:e35775. [PMID: 22567112 PMCID: PMC3342292 DOI: 10.1371/journal.pone.0035775] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 03/21/2012] [Indexed: 11/18/2022] Open
Abstract
Collodaria are the only group of Radiolaria that has a colonial lifestyle. This group is potentially the most important plankton in the oligotrophic ocean because of its large biomass and the high primary productivity associated with the numerous symbionts inside a cell or colony. The evolution of Collodaria could thus be related to the changes in paleo-productivity that have affected organic carbon fixation in the oligotrophic ocean. However, the fossil record of Collodaria is insufficient to trace their abundance through geological time, because most collodarians do not have silicified shells. Recently, molecular phylogeny based on nuclear small sub-unit ribosomal DNA (SSU rDNA) confirmed Collodaria to be one of five orders of Radiolaria, though the relationship among collodarians is still unresolved because of inadequate taxonomic sampling. Our phylogenetic analysis has revealed four novel collodarian sequences, on the basis of which collodarians can be divided into four clades that correspond to taxonomic grouping at the family level: Thalassicollidae, Collozoidae, Collosphaeridae, and Collophidae. Comparison of the results of our phylogenetic analyses with the morphological characteristics of each collodarian family suggests that the first ancestral collodarians had a solitary lifestyle and left no silica deposits. The timing of events estimated from molecular divergence calculations indicates that naked collodarian lineages first appeared around 45.6 million years (Ma) ago, coincident with the diversification of diatoms in the pelagic oceans. Colonial collodarians appeared after the formation of the present ocean circulation system and the development of oligotrophic conditions in the equatorial Pacific (ca. 33.4 Ma ago). The divergence of colonial collodarians probably caused a shift in the efficiency of primary production during this period.
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Affiliation(s)
- Yoshiyuki Ishitani
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.
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Willis K, MacDonald G. Long-Term Ecological Records and Their Relevance to Climate Change Predictions for a Warmer World. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2011. [DOI: 10.1146/annurev-ecolsys-102209-144704] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This review focuses on biotic responses during intervals of time in the fossil record when the magnitude and rate of climate change exceeded or were comparable with those predicted to occur in the next century ( Solomon et al. 2007 ). These include biotic responses during: (a) the Paleo-Eocene Thermal Maximum and early Eocene Climatic Optimum, (b) the mid-Pliocene warm interval, (c) the Eemian, and (d) the most recent glacial-interglacial transition into the Holocene. We argue that although the mechanisms responsible for these past changes in climate were different (i.e., natural processes rather than anthropogenic), the rate and magnitude of climate change were often similar to those predicted for the next century and therefore highly relevant to understanding future biotic responses. In all intervals we examine the fossil evidence for the three most commonly predicted future biotic scenarios, namely, extirpation, migration (in the form of a permanent range shift), or adaptation. Focusing predominantly on the terrestrial plant fossil record, we find little evidence for extirpation during warmer intervals; rather, range shifts, community turnover, adaptation, and sometimes an increase in diversity are observed.
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Affiliation(s)
- K.J. Willis
- Biodiversity Institute, Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom
- Department of Biology, University of Bergen, N-5020 Bergen, Norway
| | - G.M. MacDonald
- Department of Geography, University of California, Los Angeles, California 90095-1524
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24
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Haywood AM, Ridgwell A, Lunt DJ, Hill DJ, Pound MJ, Dowsett HJ, Dolan AM, Francis JE, Williams M. Are there pre-Quaternary geological analogues for a future greenhouse warming? PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:933-956. [PMID: 21282155 DOI: 10.1098/rsta.2010.0317] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Given the inherent uncertainties in predicting how climate and environments will respond to anthropogenic emissions of greenhouse gases, it would be beneficial to society if science could identify geological analogues to the human race's current grand climate experiment. This has been a focus of the geological and palaeoclimate communities over the last 30 years, with many scientific papers claiming that intervals in Earth history can be used as an analogue for future climate change. Using a coupled ocean-atmosphere modelling approach, we test this assertion for the most probable pre-Quaternary candidates of the last 100 million years: the Mid- and Late Cretaceous, the Palaeocene-Eocene Thermal Maximum (PETM), the Early Eocene, as well as warm intervals within the Miocene and Pliocene epochs. These intervals fail as true direct analogues since they either represent equilibrium climate states to a long-term CO(2) forcing--whereas anthropogenic emissions of greenhouse gases provide a progressive (transient) forcing on climate--or the sensitivity of the climate system itself to CO(2) was different. While no close geological analogue exists, past warm intervals in Earth history provide a unique opportunity to investigate processes that operated during warm (high CO(2)) climate states. Palaeoclimate and environmental reconstruction/modelling are facilitating the assessment and calculation of the response of global temperatures to increasing CO(2) concentrations in the longer term (multiple centuries); this is now referred to as the Earth System Sensitivity, which is critical in identifying CO(2) thresholds in the atmosphere that must not be crossed to avoid dangerous levels of climate change in the long term. Palaeoclimatology also provides a unique and independent way to evaluate the qualities of climate and Earth system models used to predict future climate.
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Affiliation(s)
- Alan M Haywood
- School of Earth and Environment, Earth and Environment Building, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK.
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25
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Ancient origins determine global biogeography of hot and cold desert cyanobacteria. Nat Commun 2011; 2:163. [PMID: 21266963 DOI: 10.1038/ncomms1167] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Accepted: 12/15/2010] [Indexed: 01/09/2023] Open
Abstract
Factors governing large-scale spatio-temporal distribution of microorganisms remain unresolved, yet are pivotal to understanding ecosystem value and function. Molecular genetic analyses have focused on the influence of niche and neutral processes in determining spatial patterns without considering the temporal scale. Here, we use temporal phylogenetic analysis calibrated using microfossil data for a globally sampled desert cyanobacterium, Chroococcidiopsis, to investigate spatio-temporal patterns in microbial biogeography and evolution. Multilocus phylogenetic associations were dependent on contemporary climate with no evidence for distance-related patterns. Massively parallel pyrosequencing of environmental samples confirmed that Chroococcidiopsis variants were specific to either hot or cold deserts. Temporally scaled phylogenetic analyses showed no evidence of recent inter-regional gene flow, indicating populations have not shared common ancestry since before the formation of modern continents. These results indicate that global distribution of desert cyanobacteria has not resulted from widespread contemporary dispersal but is an ancient evolutionary legacy. This highlights the importance of considering temporal scales in microbial biogeography.
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26
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Differential extinction and the contrasting structure of polar marine faunas. PLoS One 2010; 5:e15362. [PMID: 21203524 PMCID: PMC3008738 DOI: 10.1371/journal.pone.0015362] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 11/11/2010] [Indexed: 11/19/2022] Open
Abstract
Background The low taxonomic diversity of polar marine faunas today reflects both the failure of clades to colonize or diversify in high latitudes and regional extinctions of once-present clades. However, simple models of polar evolution are made difficult by the strikingly different faunal compositions and community structures of the two poles. Methodology/Principal Findings A comparison of early Cenozoic Arctic and Antarctic bivalve faunas with modern ones, within the framework of a molecular phylogeny, shows that while Arctic losses were randomly distributed across the tree, Antarctic losses were significantly concentrated in more derived families, resulting in communities dominated by basal lineages. Potential mechanisms for the phylogenetic structure to Antarctic extinctions include continental isolation, changes in primary productivity leading to turnover of both predators and prey, and the effect of glaciation on shelf habitats. Conclusions/Significance These results show that phylogenetic consequences of past extinctions can vary substantially among regions and thus shape regional faunal structures, even when due to similar drivers, here global cooling, and provide the first phylogenetic support for the “retrograde” hypothesis of Antarctic faunal evolution.
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Lu H, Wang X, Li L. Aeolian sediment evidence that global cooling has driven late Cenozoic stepwise aridification in central Asia. ACTA ACUST UNITED AC 2010. [DOI: 10.1144/sp342.4] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractIt has been a long held view that uplift of the Tibetan Plateau dominated stepwise climatic drying in central Asia during the late Cenozoic. On the other hand, global cooling may also have forced Asian drying and the subsequent formation of aeolian deposits in north China. Until now, whether the Tibetan uplift or the global cooling has been the first-order driver controlling stepwise Asian drying has remained a contentious issue. In this study, we examine the thick aeolian silt deposit, which is regarded as a good archive of palaeoclimatic changes in central Asia and north China, in order to qualitatively reconstruct the drying process in Asia during the late Cenozoic. On the basis of our long-term field surveys, laboratory analyses and previous investigations, we have obtained time sequences of Asian drying from the early Miocene to late Pleistocene; we compare this newly reconstructed time series of Asian aridification with the time series of global cooling and Tibetan uplift to identify the first-order driver of stepwise Asian aridification. A good match between the drying and global cooling might indicate that global cooling was the most likely driver of stepwise drying in interior Asia. On the other hand, controversy regarding timing and amplitude of Tibetan uplift during the late Cenozoic suggests that the prevailing conclusion that Tibetan uplift forces Asian drying should be regarded as immature. A mechanism that global cooling drove the Asian drying is tentatively suggested.
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Affiliation(s)
- H. Lu
- School of Geographic and Oceanographic Sciences, Institute for Climate and Global Change Research, Nanjing University, Nanjing 210093, China
| | - X. Wang
- School of Geographic and Oceanographic Sciences, Institute for Climate and Global Change Research, Nanjing University, Nanjing 210093, China
| | - L. Li
- School of Geographic and Oceanographic Sciences, Institute for Climate and Global Change Research, Nanjing University, Nanjing 210093, China
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Shimada T, Aplin KP, Suzuki H. Mus lepidoides (Muridae, Rodentia) of central Burma is a distinct species of potentially great evolutionary and biogeographic significance. Zoolog Sci 2010; 27:449-59. [PMID: 20443693 DOI: 10.2108/zsj.27.449] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mus lepidoides of central Burma (Myanmar) was described 75 years ago but has since been dismissed as a regional variant of the Indian field mouse, M. booduga. DNA sequences of multiple mitochondrial and nuclear genes from recently collected specimens, combined with a fresh morphological reassessment, reaffirm the distinctiveness of M. lepidoides from M. booduga and from all other species of Mus. Mus lepidoides is so distinct in fact that it warrants placement in its own Species Group within subgenus Mus. Molecular and morphological assessments of phylogenetic affinities converge on the exciting possibility that M. lepidoides represents the previously elusive sibling taxon to the Mus musculus Species Group. If confirmed, this relationship would provide the previously missing connection between the main radiation of subgenus Mus in Southeast and South Asia, and the radiation of the M. musculus Species Group in western Asia and Europe. We speculate that a common ancestor of M. lepidoides and the M. musculus Species Group occupied a continuous but episodic tract of xeric habitat that linked central Burma with northern India at various times during the late Pliocene and Quaternary. Further molecular and cytogenetic studies on the phylogenetic position of M. lepidoides clearly represent a high priority in mouse research.
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Affiliation(s)
- Tomofumi Shimada
- Laboratory of Ecology and Genetics, Graduate School of Environmental Earth Science, Hokkaido University, Kita-ku, Sapporo, Japan
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Sandve SR, Fjellheim S. Did gene family expansions during the Eocene-Oligocene boundary climate cooling play a role in Pooideae adaptation to cool climates? Mol Ecol 2010; 19:2075-88. [PMID: 20406386 DOI: 10.1111/j.1365-294x.2010.04629.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Adaptation to cool environments is a common feature in the core group of the grass subfamily Pooideae (Triticeae and Poeae). This suggest an ancient evolutionary origin of low temperature stress tolerance dating back prior to the initiation of taxonomic divergence of core Pooideae species. Viewing the Pooideae evolution in a palaeo-climatic perspective reveals that taxonomic divergence of the core Pooideae group initiated shortly after a global super-cooling period at the Eocene-Oligocene boundary (approximately 33.5-26 Ma). This global climate cooling altered distributions of plants and animals and must have imposed selection pressure for improved low temperature stress responses. Lineage-specific gene family expansions are known to be involved in adaptation to new environmental stresses. In Pooideae, two gene families involved in low temperature stress response, the C-repeat binding factor (CBF) and fructosyl transferase (FT) gene families, has undergone lineage-specific expansions. We investigated the timing of these gene family expansions by molecular dating and found that Pooideae-specific expansion events in CBF and FT gene families took place during Eocene-Oligocene super-cooling period. We hypothesize that the E-O super-cooling exerted selection pressure for improved low temperature stress response and frost tolerance in a core Pooideae ancestor, and that those individuals with multiple copies of CBF and FT genes were favoured.
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Affiliation(s)
- Simen Rød Sandve
- Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, PO Box 5003, 1431 Aas, Norway.
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Hoffmann MH, von Hagen KB, Hörandl E, Röser M, Tkach NV. SOURCES OF THE ARCTIC FLORA: ORIGINS OF ARCTIC SPECIES IN RANUNCULUS AND RELATED GENERA. INTERNATIONAL JOURNAL OF PLANT SCIENCES 2010; 171:90-106. [PMID: 20582248 PMCID: PMC2892301 DOI: 10.1086/647918] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The arctic biome is a relatively young ecosystem with ~2300 species of vascular plants. We studied the genus Ranunculus as an example of the origin and evolution of the arctic flora. For this purpose we used molecular phylogenetic and clock analyses based on evaluation of nuclear ITS and chloroplast matK-trnK DNA sequences in 194 taxa of Ranunculus and closely related genera. Taxa occurring in the Arctic arose form seven phylogenetic lineages of Ranunculus and also in the genera Coptidium and Halerpestes. Two clades of Ranunculus are species-rich in the Arctic, i.e., Ranunculus sect. Ranunculus and R. sect. Auricomus (both from R. subg. Ranunculus), but this is due to a number of arctic "microtaxa" morphologically barely separate from R. acris in the former clade and the widely agamospermic species complex of R. auricomus in the latter. Lineages with species adapted to wetlands or aquatic habitats are significant groups represented in the arctic flora (R. subg. Ranunculus sectt. Flammula and Hecatonia/Xanthobatrachium, R. subg. Batrachium, genus Coptidium) but show no clear signs of radiation in the Arctic or the northern boreal zone, except for sectt. Hecatonia/Xanthobatrachium, with R. hyperboreus and R. sceleratus subsp. reptabundus. Astonishingly few of the otherwise numerous lineages of Ranunculus with distributions in the higher mountain systems of Eurasia and North America have acted as "founding sources" for the arctic flora. The only clear example is that of the arctic-alpine R. glacialis and the Beringian R. chamissonis from the lineage of subg. R. sectt. Aconitifolii/Crymodes, although there might be others in sect. Auricomus not recovered in the current molecular data. Lineages that gave rise to arctic taxa diverged from each other from the early Miocene (R. glacialis/R. chamissonis, Coptidium, lineages in Halerpestes) and continued at an even rate throughout the Tertiary. There are no signs that the intense climate changes of the late Pliocene and the Quaternary substantially accelerated or impeded diversification in Ranunculus. Only the crown group split of R. acris and its relatives is clearly of Quaternary age. A detailed comparison concerning morphology, karyology, and life form excludes fundamental differences between taxa of Ranunculus in the Arctic and their respective closest relatives in regions south of it. Ecological traits, e.g., preferences for dry or moist soils or growth in open and sheltered conditions, also do not differ between arctic and nonarctic̣ taxa. Migration into the Arctic thus started from different phylogenetic lineages and at different times, without development of obvious special traits in the adaptation to arctic environments. This recurrent pattern in Ranunculus differs from that seen in other arctic genera, e.g., Artemisia, in which special traits of adaptation to arctic environments are found. In Ranunculus, the origin of the open arctic biome primarily favored range expansions of taxa/species already adapted to wet habitats in cold areas and depending on rapid dispersal.
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Affiliation(s)
- Matthias H. Hoffmann
- Geobotanik und Botanischer Garten, Martin-Luther-Universität Halle-Wittenberg, Institut für Biologie, Am Kirchtor 3, 06108 Halle, Germany
| | - K. Bernhard von Hagen
- Geobotanik und Botanischer Garten, Martin-Luther-Universität Halle-Wittenberg, Institut für Biologie, Am Kirchtor 3, 06108 Halle, Germany
| | - Elvira Hörandl
- Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, 1030 Vienna, Austria
| | - Martin Röser
- Geobotanik und Botanischer Garten, Martin-Luther-Universität Halle-Wittenberg, Institut für Biologie, Am Kirchtor 3, 06108 Halle, Germany
| | - Natalia V. Tkach
- Geobotanik und Botanischer Garten, Martin-Luther-Universität Halle-Wittenberg, Institut für Biologie, Am Kirchtor 3, 06108 Halle, Germany
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31
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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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32
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The future of ice sheets and sea ice: between reversible retreat and unstoppable loss. Proc Natl Acad Sci U S A 2009; 106:20590-5. [PMID: 19884496 DOI: 10.1073/pnas.0902356106] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We discuss the existence of cryospheric "tipping points" in the Earth's climate system. Such critical thresholds have been suggested to exist for the disappearance of Arctic sea ice and the retreat of ice sheets: Once these ice masses have shrunk below an anticipated critical extent, the ice-albedo feedback might lead to the irreversible and unstoppable loss of the remaining ice. We here give an overview of our current understanding of such threshold behavior. By using conceptual arguments, we review the recent findings that such a tipping point probably does not exist for the loss of Arctic summer sea ice. Hence, in a cooler climate, sea ice could recover rapidly from the loss it has experienced in recent years. In addition, we discuss why this recent rapid retreat of Arctic summer sea ice might largely be a consequence of a slow shift in ice-thickness distribution, which will lead to strongly increased year-to-year variability of the Arctic summer sea-ice extent. This variability will render seasonal forecasts of the Arctic summer sea-ice extent increasingly difficult. We also discuss why, in contrast to Arctic summer sea ice, a tipping point is more likely to exist for the loss of the Greenland ice sheet and the West Antarctic ice sheet.
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Evidence for middle Eocene Arctic sea ice from diatoms and ice-rafted debris. Nature 2009; 460:376-9. [PMID: 19606146 DOI: 10.1038/nature08163] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Accepted: 05/21/2009] [Indexed: 11/08/2022]
Abstract
Oceanic sediments from long cores drilled on the Lomonosov ridge, in the central Arctic, contain ice-rafted debris (IRD) back to the middle Eocene epoch, prompting recent suggestions that ice appeared in the Arctic about 46 million years (Myr) ago. However, because IRD can be transported by icebergs (derived from land-based ice) and also by sea ice, IRD records are restricted to providing a history of general ice-rafting only. It is critical to differentiate sea ice from glacial (land-based) ice as climate feedback mechanisms vary and global impacts differ between these systems: sea ice directly affects ocean-atmosphere exchanges, whereas land-based ice affects sea level and consequently ocean acidity. An earlier report assumed that sea ice was prevalent in the middle Eocene Arctic on the basis of IRD, and although somewhat preliminary supportive evidence exists, these data are neither comprehensive nor quantified. Here we show the presence of middle Eocene Arctic sea ice from an extraordinary abundance of a group of sea-ice-dependent fossil diatoms (Synedropsis spp.). Analysis of quartz grain textural characteristics further supports sea ice as the dominant transporter of IRD at this time. Together with new information on cosmopolitan diatoms and existing IRD records, our data strongly suggest a two-phase establishment of sea ice: initial episodic formation in marginal shelf areas approximately 47.5 Myr ago, followed approximately 0.5 Myr later by the onset of seasonally paced sea-ice formation in offshore areas of the central Arctic. Our data establish a 2-Myr record of sea ice, documenting the transition from a warm, ice-free environment to one dominated by winter sea ice at the start of the middle Eocene climatic cooling phase.
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Davies A, Kemp AES, Pike J. Late Cretaceous seasonal ocean variability from the Arctic. Nature 2009; 460:254-8. [PMID: 19587768 DOI: 10.1038/nature08141] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Accepted: 05/13/2009] [Indexed: 11/10/2022]
Abstract
The modern Arctic Ocean is regarded as a barometer of global change and amplifier of global warming and therefore records of past Arctic change are critical for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the Late Cretaceous epoch (65-99 million years ago), yet records from such times may yield important clues to Arctic Ocean behaviour in near-future warmer climates. Here we present a seasonally resolved Cretaceous sedimentary record from the Alpha ridge of the Arctic Ocean. This palaeo-sediment trap provides new insight into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized. Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific subtropical gyre, or those indicated for the Mediterranean sapropels. With increased CO(2) levels and warming currently driving increased stratification in the global ocean, this style of production that is adapted to stratification may become more widespread. Our evidence for seasonal diatom production and flux testify to an ice-free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low temperatures in the Late Cretaceous Arctic Ocean, rather than recent suggestions of a 15 degrees C mean annual temperature at this time.
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Affiliation(s)
- Andrew Davies
- National Oceanography Centre Southampton, School of Ocean and Earth Science, University of Southampton, Southampton, SO14 3ZH, UK
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Increased seasonality through the Eocene to Oligocene transition in northern high latitudes. Nature 2009; 459:969-73. [DOI: 10.1038/nature08069] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Accepted: 04/09/2009] [Indexed: 11/09/2022]
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Forschner SR, Sheffer R, Rowley DC, Smith DC. Microbial diversity in Cenozoic sediments recovered from the Lomonosov Ridge in the Central Arctic Basin. Environ Microbiol 2009; 11:630-9. [DOI: 10.1111/j.1462-2920.2008.01834.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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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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Hoffmann MH, Röser M. Taxon recruitment of the arctic flora: an analysis of phylogenies. THE NEW PHYTOLOGIST 2009; 182:774-780. [PMID: 19309448 DOI: 10.1111/j.1469-8137.2009.02782.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The Arctic is the endpoint of many climatic gradients and is presently occupied by c. 2200 vascular plant species. Glaciation started in the Middle Eocene but a significant expansion of the Greenland ice shield occurred only c. 3.2 million yr ago, leading to the expansion of the treeless circumpolar arctic tundra. Available molecular phylogenetic studies were evaluated for 148 of 374 genera occurring in the Arctic to determine the relative roles of their independent origins and their diversification in the development of the contemporary arctic flora. The number of arctic species paralleled the total number of species in a genus. Multiple arctic species within a genus originated mostly independently of each other and from different lineages. Minor radiations occurred in only a few genera and major radiations were absent. Mostly parallel evolution of arctic taxa from nonarctic ancestors, supposedly of different ages of origin, scarcity of radiations and rarity of endemics are main features of the arctic flora.
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Affiliation(s)
- Matthias H Hoffmann
- Martin-Luther-University Halle-Wittenberg, Institute of Biology, Am Kirchtor 3, D-06108 Halle, Germany
| | - Martin Röser
- Martin-Luther-University Halle-Wittenberg, Institute of Biology, Am Kirchtor 3, D-06108 Halle, Germany
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Reid PC, Fischer AC, Lewis-Brown E, Meredith MP, Sparrow M, Andersson AJ, Antia A, Bates NR, Bathmann U, Beaugrand G, Brix H, Dye S, Edwards M, Furevik T, Gangstø R, Hátún H, Hopcroft RR, Kendall M, Kasten S, Keeling R, Le Quéré C, Mackenzie FT, Malin G, Mauritzen C, Olafsson J, Paull C, Rignot E, Shimada K, Vogt M, Wallace C, Wang Z, Washington R. Chapter 1. Impacts of the oceans on climate change. ADVANCES IN MARINE BIOLOGY 2009; 56:1-150. [PMID: 19895974 DOI: 10.1016/s0065-2881(09)56001-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The oceans play a key role in climate regulation especially in part buffering (neutralising) the effects of increasing levels of greenhouse gases in the atmosphere and rising global temperatures. This chapter examines how the regulatory processes performed by the oceans alter as a response to climate change and assesses the extent to which positive feedbacks from the ocean may exacerbate climate change. There is clear evidence for rapid change in the oceans. As the main heat store for the world there has been an accelerating change in sea temperatures over the last few decades, which has contributed to rising sea-level. The oceans are also the main store of carbon dioxide (CO2), and are estimated to have taken up approximately 40% of anthropogenic-sourced CO2 from the atmosphere since the beginning of the industrial revolution. A proportion of the carbon uptake is exported via the four ocean 'carbon pumps' (Solubility, Biological, Continental Shelf and Carbonate Counter) to the deep ocean reservoir. Increases in sea temperature and changing planktonic systems and ocean currents may lead to a reduction in the uptake of CO2 by the ocean; some evidence suggests a suppression of parts of the marine carbon sink is already underway. While the oceans have buffered climate change through the uptake of CO2 produced by fossil fuel burning this has already had an impact on ocean chemistry through ocean acidification and will continue to do so. Feedbacks to climate change from acidification may result from expected impacts on marine organisms (especially corals and calcareous plankton), ecosystems and biogeochemical cycles. The polar regions of the world are showing the most rapid responses to climate change. As a result of a strong ice-ocean influence, small changes in temperature, salinity and ice cover may trigger large and sudden changes in regional climate with potential downstream feedbacks to the climate of the rest of the world. A warming Arctic Ocean may lead to further releases of the potent greenhouse gas methane from hydrates and permafrost. The Southern Ocean plays a critical role in driving, modifying and regulating global climate change via the carbon cycle and through its impact on adjacent Antarctica. The Antarctic Peninsula has shown some of the most rapid rises in atmospheric and oceanic temperature in the world, with an associated retreat of the majority of glaciers. Parts of the West Antarctic ice sheet are deflating rapidly, very likely due to a change in the flux of oceanic heat to the undersides of the floating ice shelves. The final section on modelling feedbacks from the ocean to climate change identifies limitations and priorities for model development and associated observations. Considering the importance of the oceans to climate change and our limited understanding of climate-related ocean processes, our ability to measure the changes that are taking place are conspicuously inadequate. The chapter highlights the need for a comprehensive, adequately funded and globally extensive ocean observing system to be implemented and sustained as a high priority. Unless feedbacks from the oceans to climate change are adequately included in climate change models, it is possible that the mitigation actions needed to stabilise CO2 and limit temperature rise over the next century will be underestimated.
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Affiliation(s)
- Philip C Reid
- Sir Alister Hardy Foundation for Ocean Science, The Laboratory, Citadel Hill, Plymouth PL1 2PB, United Kingdom
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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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Greene CH, Pershing AJ, Cronin TM, Ceci N. ARCTIC CLIMATE CHANGE AND ITS IMPACTS ON THE ECOLOGY OF THE NORTH ATLANTIC. Ecology 2008; 89:S24-38. [PMID: 19097482 DOI: 10.1890/07-0550.1] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Charles H Greene
- Ocean Resources and Ecosystems Program, Snee Hall, Cornell University, Ithaca, New York 14853, USA.
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Abstract
India's northward flight and collision with Asia was a major driver of global tectonics in the Cenozoic and, we argue, of atmospheric CO(2) concentration (pCO(2)) and thus global climate. Subduction of Tethyan oceanic crust with a carpet of carbonate-rich pelagic sediments deposited during transit beneath the high-productivity equatorial belt resulted in a component flux of CO(2) delivery to the atmosphere capable to maintain high pCO(2) levels and warm climate conditions until the decarbonation factory shut down with the collision of Greater India with Asia at the Early Eocene climatic optimum at approximately 50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO(2) by efficient silicate weathering further perturbed the delicate equilibrium between CO(2) input to and removal from the atmosphere toward progressively lower pCO(2) levels, thus marking the onset of a cooling trend over the Middle and Late Eocene that some suggest triggered the rapid expansion of Antarctic ice sheets at around the Eocene-Oligocene boundary.
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Graham LA, Lougheed SC, Ewart KV, Davies PL. Lateral transfer of a lectin-like antifreeze protein gene in fishes. PLoS One 2008; 3:e2616. [PMID: 18612417 PMCID: PMC2440524 DOI: 10.1371/journal.pone.0002616] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2008] [Accepted: 06/05/2008] [Indexed: 11/18/2022] Open
Abstract
Fishes living in icy seawater are usually protected from freezing by endogenous antifreeze proteins (AFPs) that bind to ice crystals and stop them from growing. The scattered distribution of five highly diverse AFP types across phylogenetically disparate fish species is puzzling. The appearance of radically different AFPs in closely related species has been attributed to the rapid, independent evolution of these proteins in response to natural selection caused by sea level glaciations within the last 20 million years. In at least one instance the same type of simple repetitive AFP has independently originated in two distant species by convergent evolution. But, the isolated occurrence of three very similar type II AFPs in three distantly related species (herring, smelt and sea raven) cannot be explained by this mechanism. These globular, lectin-like AFPs have a unique disulfide-bonding pattern, and share up to 85% identity in their amino acid sequences, with regions of even higher identity in their genes. A thorough search of current databases failed to find a homolog in any other species with greater than 40% amino acid sequence identity. Consistent with this result, genomic Southern blots showed the lectin-like AFP gene was absent from all other fish species tested. The remarkable conservation of both intron and exon sequences, the lack of correlation between evolutionary distance and mutation rate, and the pattern of silent vs non-silent codon changes make it unlikely that the gene for this AFP pre-existed but was lost from most branches of the teleost radiation. We propose instead that lateral gene transfer has resulted in the occurrence of the type II AFPs in herring, smelt and sea raven and allowed these species to survive in an otherwise lethal niche.
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Affiliation(s)
- Laurie A. Graham
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada
| | | | - K. Vanya Ewart
- NRC Institute for Marine Biosciences, Halifax, Nova Scotia, Canada
| | - Peter L. Davies
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada
- Department of Biology, Queen's University, Kingston, Ontario, Canada
- NRC Institute for Marine Biosciences, Halifax, Nova Scotia, Canada
- * E-mail:
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Lundberg JG, Sullivan JP, Rodiles-Hernández R, Hendrickson DA. Discovery of African roots for the Mesoamerican Chiapas catfish, Lacantunia enigmatica, requires an ancient intercontinental passage. PROCEEDINGS OF THE ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA 2007. [DOI: 10.1635/0097-3157(2007)156[39:doarft]2.0.co;2] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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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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Jakobsson M, Backman J, Rudels B, Nycander J, Frank M, Mayer L, Jokat W, Sangiorgi F, O'Regan M, Brinkhuis H, King J, Moran K. The early Miocene onset of a ventilated circulation regime in the Arctic Ocean. Nature 2007; 447:986-90. [PMID: 17581581 DOI: 10.1038/nature05924] [Citation(s) in RCA: 179] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Accepted: 05/10/2007] [Indexed: 11/08/2022]
Abstract
Deep-water formation in the northern North Atlantic Ocean and the Arctic Ocean is a key driver of the global thermohaline circulation and hence also of global climate. Deciphering the history of the circulation regime in the Arctic Ocean has long been prevented by the lack of data from cores of Cenozoic sediments from the Arctic's deep-sea floor. Similarly, the timing of the opening of a connection between the northern North Atlantic and the Arctic Ocean, permitting deep-water exchange, has been poorly constrained. This situation changed when the first drill cores were recovered from the central Arctic Ocean. Here we use these cores to show that the transition from poorly oxygenated to fully oxygenated ('ventilated') conditions in the Arctic Ocean occurred during the later part of early Miocene times. We attribute this pronounced change in ventilation regime to the opening of the Fram Strait. A palaeo-geographic and palaeo-bathymetric reconstruction of the Arctic Ocean, together with a physical oceanographic analysis of the evolving strait and sill conditions in the Fram Strait, suggests that the Arctic Ocean went from an oxygen-poor 'lake stage', to a transitional 'estuarine sea' phase with variable ventilation, and finally to the fully ventilated 'ocean' phase 17.5 Myr ago. The timing of this palaeo-oceanographic change coincides with the onset of the middle Miocene climatic optimum, although it remains unclear if there is a causal relationship between these two events.
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Affiliation(s)
- Martin Jakobsson
- Department of Geology and Geochemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
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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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