Geographic patterns of genetic diversity in North American trees: a continent-wide analysis

2021 ◽  
Author(s):  
Andrew V. Gougherty
Keyword(s):  
Genetic Diversity ◽  
Population Genetics ◽  
North America ◽  
North American ◽  
Tree Species ◽  
Geographic Patterns ◽  
Study Characteristics ◽  
Dispersal Traits ◽  
The Last Glacial Maximum ◽  
The Last Glacial

In the northern hemisphere, many species have been reported to have greater genetic diversity in southern populations than northern populations - ostensibly due to migration northward following the last glacial maximum (LGM). The generality of this pattern, while well-established for some taxa, remains unclear for North American trees. To address this issue, I collected published population genetics data for 73 North American tree species, and tested whether genetic diversity was associated with latitude or longitude and whether geographic trends were associated with dispersal traits, range or study characteristics. I found there were no general geographic patterns in genetic diversity, and the strength of the geographic gradients were not associated with any species or study characteristics. Species in the northern and western regions of North America tended to have more species with genetic diversity that declined with latitude, but most species had no significant trend. This work shows that North American trees have complex, individualistic, patterns of genetic diversity that may negate explanation by any particular dispersal trait or range characteristic.

scholarly journals Distorted Pacific–North American teleconnection at the Last Glacial Maximum

2020 ◽  
Vol 16 (1) ◽  
pp. 199-209 ◽  
Author(s):  
Yongyun Hu ◽  
Yan Xia ◽  
Zhengyu Liu ◽  
Yuchen Wang ◽  
Zhengyao Lu ◽  
...  
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
North American ◽  
Tropical Pacific ◽  
Glacial Maximum ◽  
Jet Stream ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Tropical Pacific ◽  
The Last Glacial

Abstract. The Pacific–North American (PNA) teleconnection is one of the most important climate modes in the present climate condition, and it enables climate variations in the tropical Pacific to exert a significant influence on North America. Here, we show climate simulations in which the PNA teleconnection was largely distorted or broken at the Last Glacial Maximum (LGM). The distorted PNA is caused by a split in the westerly jet stream, which is ultimately forced by the large, thick Laurentide ice sheet that was present at the LGM. Changes in the jet stream greatly alter the extratropical waveguide, distorting wave propagation from the North Pacific to North America. The distorted PNA suggests that climate variability in the tropical Pacific, notably El Niño–Southern Oscillation (ENSO), would have little direct impact on North American climate at the LGM.

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 The Effects of the Laurentide Ice Sheet on North American Climate during the Last Glacial Maximum

2008 ◽  
Vol 41 (2) ◽  
pp. 291-299 ◽  
Author(s):  
A. J. Broccoli ◽  
S. Manabe
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
North American ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Laurentide Ice Sheet ◽  
Last Glacial ◽  
North American Climate ◽  
The Last Glacial Maximum ◽  
The Last Glacial

ABSTRACT A climate model, consisting of an atmospheric general circulation model coupled with a simple model of the oceanic mixed layer, is used to investigate the effects of the continental ice distribution of the last glacial maximum (LGM) on North American climate. This model has previously been used to simulate the LGM climate, producing temperature changes reasonably in agreement with paleoclimatic data. The LGM distribution of continental ice according to the maximum reconstruction of HUGHES et al. (1981) is used as input to the model. In response to the incorporation of the expanded continental ice of the LGM, the model produces major changes in the climate of North America. The ice sheet exerts an orographic effect on the tropospheric flow, resulting in a splitting of the midlatitude westerlies in all seasons but summer. Winter temperatures are greatly reduced over a wide region south of the Laurentide ice sheet, although summer cooling is less extensive. An area of reduced soil moisture develops in the interior of North America just south of the ice margin. At the same time, precipitation increases in a belt extending from the extreme southeastern portion of the ice sheet eastward into the North Atlantic. Some of these findings are similar to paleoclimatic inferences based on geological evidence.

scholarly journals Ancient genomes redate the extinction of Sussemionus, a subgenus of Equus, to late Holocene

2021 ◽  
Author(s):  
Dawei Cai ◽  
Siqi Zhu ◽  
Mian Gong ◽  
Naifan Zhang ◽  
Jia Wen ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
North America ◽  
Ancient Dna ◽  
Fossil Record ◽  
Late Holocene ◽  
Northern China ◽  
High Quality ◽  
The Last Glacial Maximum ◽  
The Last Glacial

The exceptionally-rich fossil record available for the equid family has provided textbook examples of macroevolutionary changes. Horses, asses and zebras represent three extant subgenus of Equus lineage, while the Sussemionus subgenus is another remarkable Equus lineage ranging from North America to Ethiopia in Pleistocene. We sequenced 26 archaeological specimens from northern China in Holocene showing morphological features reminiscent of Equus ovodovi, a species representative of Sussemionus, and further confirmed them as this species by genetic analyses. Thus, we present the first high-quality complete genome of the Sussemionus that we sequenced to 12.0× depth-of-coverage and demonstrate that it survived until ~3,500 years ago, despite the continued demographic collapse during the Last Glacial Maximum and the great human expansion in East Asia. We also confirmed the Equus tree, and found Sussemionus diverged from the ancestor of non-caballine equids ~2.3-2.7 Million years ago and admixture events could have taken place between them. Our works suggest the small genetic diversity but not the enhanced inbreeding mainly limited the chances of survival of the species, and illustrates how ancient DNA can inform on extinction dynamics and the long-term resilience of species surviving in cryptic population pockets.

scholarly journals Distorted Pacific-North American Teleconnection at the Last Glacial Maximum

2019 ◽  
Author(s):  
Yongyun Hu ◽  
Yan Xia ◽  
Zhengyu Liu ◽  
Yuchen Wang ◽  
Zhengyao Lu ◽  
...  
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
North American ◽  
Tropical Pacific ◽  
Glacial Maximum ◽  
Jet Stream ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Tropical Pacific ◽  
The Last Glacial

Abstract. The Pacific-North American (PNA) teleconnection is one of the most important climate modes in the present climate condition, and it enables climate variations in the tropical Pacific to exert significant impacts on North America. Here, we show climate simulations that the PNA teleconnection was largely distorted or broken at the Last Glacial Maximum (LGM). The distorted PNA is caused by a split of the westerly jet stream, which is ultimately forced by the thick and large Laurentide ice sheet at the LGM. Changes in the jet stream greatly alter the extratropical wave guide, distorting wave propagation from the North Pacific to North America. The distorted PNA suggests that climate variability in the tropical Pacific, notably, El Niño and Southern Oscillation (ENSO), would have little direct impact on North American climate at the LGM.

scholarly journals Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum

2016 ◽  
Vol 4 (4) ◽  
pp. 831-869 ◽  
Author(s):  
Andrew D. Wickert
Keyword(s):  
North American ◽  
Drainage Basin ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Drainage Basins ◽  
Last Glacial ◽  
Isostatic Adjustment ◽  
The North ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Over the last glacial cycle, ice sheets and the resultant glacial isostatic adjustment (GIA) rearranged river systems. As these riverine threads that tied the ice sheets to the sea were stretched, severed, and restructured, they also shrank and swelled with the pulse of meltwater inputs and time-varying drainage basin areas, and sometimes delivered enough meltwater to the oceans in the right places to influence global climate. Here I present a general method to compute past river flow paths, drainage basin geometries, and river discharges, by combining models of past ice sheets, glacial isostatic adjustment, and climate. The result is a time series of synthetic paleohydrographs and drainage basin maps from the Last Glacial Maximum to present for nine major drainage basins – the Mississippi, Rio Grande, Colorado, Columbia, Mackenzie, Hudson Bay, Saint Lawrence, Hudson, and Susquehanna/Chesapeake Bay. These are based on five published reconstructions of the North American ice sheets. I compare these maps with drainage reconstructions and discharge histories based on a review of observational evidence, including river deposits and terraces, isotopic records, mineral provenance markers, glacial moraine histories, and evidence of ice stream and tunnel valley flow directions. The sharp boundaries of the reconstructed past drainage basins complement the flexurally smoothed GIA signal that is more often used to validate ice-sheet reconstructions, and provide a complementary framework to reduce nonuniqueness in model reconstructions of the North American ice-sheet complex.

scholarly journals High unexpected genetic diversity of a narrow endemic terrestrial mollusc

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3069 ◽  
Author(s):  
Pedro M. Madeira ◽  
Rosa M. Chefaoui ◽  
Regina L. Cunha ◽  
Francisco Moreira ◽  
Susana Dias ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Sequence Data ◽  
Land Snails ◽  
Physical Conditions ◽  
Narrow Endemic ◽  
Terrestrial Mollusc ◽  
Central Portugal ◽  
Genetic Survey ◽  
The Last Glacial Maximum ◽  
The Last Glacial

The Iberian Peninsula has an extensive record of species displaying strong genetic structure as a result of their survival in isolated pockets throughout the Pleistocene ice ages. We used mitochondrial and nuclear sequence data to analyze phylogeographic patterns in endemic land snails from a valley of central Portugal (Vale da Couda), putatively assigned toCandidula coudensis, that show an exceptionally narrow distributional range. The genetic survey presented here shows the existence of five main mitochondrial lineages in Vale da Couda that do not cluster together suggesting independent evolutionary histories. Our results also indicate a departure from the expectation that species with restricted distributions have low genetic variability. The putative past and contemporary models of geographic distribution of Vale da Couda lineages are compatible with a scenario of species co-existence in more southern locations during the last glacial maximum (LGM) followed by a post-LGM northern dispersal tracking the species optimal thermal, humidity and soil physical conditions.

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