Present-Day Genetic Structure of the Holoparasite Conopholis americana (Orobanchaceae) in Eastern North America and the Location of Its Refugia during the Last Glacial Cycle

2016 ◽  
Vol 177 (2) ◽  
pp. 132-144 ◽  
Author(s):  
Anuar Rodrigues ◽  
Saša Stefanović
Keyword(s):  
Genetic Structure ◽  
North America ◽  
Eastern North America ◽  
Glacial Cycle ◽  
Last Glacial ◽  
The Last Glacial

Vegetation and environment in Eastern North America during the Last Glacial Maximum

2000 ◽  
Vol 19 (6) ◽  
pp. 489-508 ◽  
Author(s):  
Stephen T. Jackson ◽  
Robert S. Webb ◽  
Katharine H. Anderson ◽  
Jonathan T. Overpeck ◽  
Thompson Webb III ◽  
...  
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Eastern North America ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Millennial-scale variations in western Sierra Nevada precipitation during the last glacial cycle MIS 4/3 transition

2014 ◽  
Vol 82 (1) ◽  
pp. 236-248 ◽  
Author(s):  
Jessica L. Oster ◽  
Isabel P. Montañez ◽  
Regina Mertz-Kraus ◽  
Warren D. Sharp ◽  
Greg M. Stock ◽  
...  
Keyword(s):  
North America ◽  
Sierra Nevada ◽  
Western Slope ◽  
Western North America ◽  
Glacial Cycle ◽  
Climatic Response ◽  
Last Glacial ◽  
Mis 3 ◽  
Heinrich Event ◽  
The Last Glacial

AbstractDansgaard–Oeschger (D–O) cycles had far-reaching effects on Northern Hemisphere and tropical climate systems during the last glacial period, yet the climatic response to D–O cycles in western North America is controversial, especially prior to 55 ka. We document changes in precipitation along the western slope of the central Sierra Nevada during early Marine Oxygen Isotope Stages (MIS) 3 and 4 (55–67 ka) from a U-series dated speleothem record from McLean's Cave. The timing of our multi-proxy geochemical dataset is coeval with D–O interstadials (15–18) and stadials, including Heinrich Event 6. The McLean's Cave stalagmite indicates warmer and drier conditions during Greenland interstadials (GISs 15–18), signified by elevated δ18O, δ13C, reflectance, and trace element concentrations, and less radiogenic 87Sr/86Sr. Our record extends evidence of a strong linkage between high-latitude warming and reduced precipitation in western North America to early MIS 3 and MIS 4. This record shows that the linkage persists in diverse global climate states, and documents the nature of the climatic response in central California to Heinrich Event 6.

scholarly journals Genomic evidence of a widespread southern distribution during the Last Glacial Maximum for two eastern North American hickory species

2017 ◽  
Author(s):  
Jordan B. Bemmels ◽  
Christopher W. Dick
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
North America ◽  
Last Glacial Maximum ◽  
Temperate Forest ◽  
Eastern North America ◽  
Carya Ovata ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AimPhylogeographic studies of temperate forest taxa often infer complex histories involving population subdivision into distinct refugia during the Last Glacial Maximum (LGM). However, temperate forests may have been broadly distributed in southeastern North America during the LGM. We investigate genome-wide genetic structure in two widespread eastern North America tree species to determine if range expansion from a contiguous area or from genetically isolated refugia better explains the postglacial history of trees and forests from this region.LocationEastern North America (ENA).TaxaBitternut hickory (Carya cordiformis (Wangenh.) K.Koch) and shagbark hickory (Carya ovata (Mill.) K.Koch).MethodsGenetic diversity and differentiation indices were calculated from >1,000 nuclear SNP loci genotyped in ca. 180 individuals per species sampled across ENA. Genetic structure was investigated using principle component analysis and genetic clustering algorithms. As an additional tool for inference, areas of suitable habitat during the LGM were predicted using species distribution models (SDMs).ResultsPopulations across all latitudes showed similar levels of genetic diversity. Most genetic variation was weakly differentiated across ENA, with the exception of an outlier population of Carya ovata in Texas. Genetic structure in each species exhibited an isolation-by-distance pattern. SDMs predicted high LGM habitat suitability over much of the southeastern United States.Main conclusionsBoth hickory species likely survived the LGM in a large region of continuous habitat and recolonized northern areas in a single expanding front that encountered few migration barriers. More complex scenarios, such as forest refugia, need not be invoked to explain genetic structure. The genetically distinct Texas population of Carya ovata could represent a separate glacial refugium, but other explanations are possible. Relative to that of other temperate forest regions, the phylogeographic history of ENA may have been exceptionally simple, involving a northward range shift but without well defined refugia.

scholarly journals Numerical studies on the Impact of the Last Glacial Cycle on recent borehole temperature profiles: implications for terrestrial energy balance

2014 ◽  
Vol 10 (5) ◽  
pp. 1693-1706 ◽  
Author(s):  
H. Beltrami ◽  
G. S. Matharoo ◽  
L. Tarasov ◽  
V. Rath ◽  
J. E. Smerdon
Keyword(s):  
Steady State ◽  
North America ◽  
Heat Content ◽  
Temperature Profiles ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Steady State Temperature ◽  
Borehole Temperature ◽  
The Impact ◽  
The Last Glacial

Abstract. Reconstructions of past climatic changes from borehole temperature profiles are important independent estimates of temperature histories over the last millennium. There remain, however, multiple uncertainties in the interpretation of these data as climatic indicators and as estimates of the changes in the heat content of the continental subsurface due to long-term climatic change. One of these uncertainties is associated with the often ignored impact of the last glacial cycle (LGC) on the subsurface energy content, and on the estimate of the background quasi steady-state signal associated with the diffusion of accretionary energy from the Earth's interior. Here, we provide the first estimate of the impact of the development of the Laurentide ice sheet on the estimates of energy and temperature reconstructions from measurements of terrestrial borehole temperatures in North America. We use basal temperature values from the data-calibrated Memorial University of Newfoundland glacial systems model (MUN-GSM) to quantify the extent of the perturbation to estimated steady-state temperature profiles, and to derive spatial maps of the expected impacts on measured profiles over North America. Furthermore, we present quantitative estimates of the potential effects of temperature changes during the last glacial cycle on the borehole reconstructions over the last millennium for North America. The range of these possible impacts is estimated using synthetic basal temperatures for a period covering 120 ka to the present day that include the basal temperature history uncertainties from an ensemble of results from the calibrated numerical model. For all the locations, we find that within the depth ranges that are typical for available boreholes (≈600 m), the induced perturbations to the steady-state temperature profile are on the order of 10 mW m−2, decreasing with greater depths. Results indicate that site-specific heat content estimates over North America can differ by as much as 50%, if the energy contribution of the last glacial cycle in those areas of North America that experienced glaciation is not taken into account when estimating recent subsurface energy changes from borehole temperature data.

Modeling North American Freshwater Runoff through the Last Glacial Cycle

1999 ◽  
Vol 52 (3) ◽  
pp. 300-315 ◽  
Author(s):  
Shawn J. Marshall ◽  
Garry K.C. Clarke
Keyword(s):  
North America ◽  
North Atlantic ◽  
Ice Sheets ◽  
Ice Sheet ◽  
High Amplitude ◽  
Ice Age ◽  
Glacial Cycle ◽  
Ice Dynamics ◽  
Last Glacial ◽  
The Last Glacial

The Northern Hemisphere ice sheets decayed rapidly during deglacial phases of the ice-age cycle, producing meltwater fluxes that may have been of sufficient magnitude to perturb oceanic circulation. The continental record of ice-sheet history is more obscured during the growth and advance of the last great ice sheets, ca. 120,000–20,000 yr B.P., but ice cores tell of high-amplitude, millennial-scale climate fluctuations that prevailed throughout this period. These climatic excursions would have provoked significant fluctuation of ice-sheet margins and runoff variability whenever ice sheets extended to mid-latitudes, giving a complex pattern of freshwater delivery to the oceans. A model of continental surface hydrology is coupled with an ice-dynamics model simulating the last glacial cycle in North America. Meltwater discharged from ice sheets is either channeled down continental drainage pathways or stored temporarily in large systems of proglacial lakes that border the retreating ice-sheet margin. The coupled treatment provides quantitative estimates of the spatial and temporal patterns of freshwater flux to the continental margins. Results imply an intensified surface hydrological environment when ice sheets are present, despite a net decrease in precipitation during glacial periods. Diminished continental evaporation and high levels of meltwater production combine to give mid-latitude runoff values that are highly variable through the glacial cycle, but are two to three times in excess of modern river fluxes; drainage to the North Atlantic via the St. Lawrence, Hudson, and Mississippi River catchments averages 0.356 Sv for the period 60,000–10,000 yr B.P., compared to 0.122 Sv for the past 10,000 yr. High-amplitude meltwater pulses to the Gulf of Mexico, North Atlantic, and North Pacific occur throughout the glacial period, with ice-sheet geometry controlling intricate patterns of freshwater routing variability. Runoff from North America is staged in the final deglaciation, with a stepped sequence of pulses through the Mississippi, St. Lawrence, Arctic, and Hudson Strait drainages.

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