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Steppe-tundra composition and deglacial floristic turnover in interior Alaska revealed by sedimentary ancient DNA (sedaDNA)

Steppe-tundra composition and deglacial floristic turnover in interior Alaska revealed by sedimentary ancient DNA (sedaDNA)
Steppe-tundra composition and deglacial floristic turnover in interior Alaska revealed by sedimentary ancient DNA (sedaDNA)
When tracing vegetation dynamics over long timescales, obtaining enough floristic information to gain a detailed understanding of past communities and their transitions can be challenging. The first high-resolution sedimentary DNA (sedaDNA) metabarcoding record from lake sediments in Alaska—reported here—covers nearly 15,000 years of change. It shows in unprecedented detail the composition of late-Pleistocene “steppe-tundra” vegetation of ice-free Alaska, part of an intriguing late-Quaternary “no-analogue” biome, and it covers the subsequent changes that led to the development of modern spruce-dominated boreal forest. The site (Chisholm Lake) lies close to key archaeological sites, and the record throws new light on the landscape and resources available to early humans. Initially, vegetation was dominated by forbs found in modern tundra and/or subarctic steppe vegetation (e.g., Potentilla, Draba, Eritrichium, Anemone patens), and graminoids (e.g., Bromus pumpellianus, Festuca, Calamagrostis, Puccinellia), with Salix the only prominent woody taxon. Predominantly xeric, warm-to-cold habitats are indicated, and we explain the mixed ecological preferences of the fossil assemblages as a topo-mosaic strongly affected by insolation load. At ca. 14,500 cal. yr BP (calendar years before C.E. 1950), about the same time as well documented human arrivals and coincident with an increase in effective moisture, Betula expanded. Graminoids became less abundant, but many open-ground forb taxa persisted. This woody-herbaceous mosaic is compatible with the observed persistence of Pleistocene megafaunal species (animals weighing ≥44 kg)—important resources for early humans. The greatest taxonomic turnover, marking a transition to regional woodland and a further moisture increase, began ca. 11,000 cal. yr BP when Populus expanded, along with new shrub taxa (e.g., Shepherdia, Eleagnus, Rubus, Viburnum). Picea then expanded ca. 9500 cal. yr BP, along with shrub and forb taxa typical of evergreen boreal woodland (e.g., Spiraea, Cornus, Linnaea). We found no evidence for Picea in the late-Pleistocene, however. Most taxa present today were established by ca. 5000 cal. yr BP after almost complete taxonomic turnover since the start of the record (though Larix appeared only at ca. 1500 cal. yr BP). Prominent fluctuations in aquatic communities ca. 14,000 - 9,500 cal. yr BP are probably related to lake-level fluctuations prior to the lake reaching its high, near-modern depth ca. 8,000 cal. yr BP.
aquatic macrophytes, diversity, flora, mammalian resources, topoclimate, Flora, Aquatic macrophytes, Diversity, Mammalian resources, Topoclimate
0277-3791
Clarke, Charlotte
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Monteath, Alistair
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Hughes, Paul
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Alsos, Inger
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Heintzman, Peter
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Lammers, Youri
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Bigelow, Nancy
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Reuther, Joshua
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Potter, Ben
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Edwards, Mary
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Clarke, Charlotte
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Monteath, Alistair
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Hughes, Paul
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Alsos, Inger
03651a9e-708a-4b04-adc7-fa6aebca3bb0
Heintzman, Peter
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Lammers, Youri
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Bigelow, Nancy
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Reuther, Joshua
89de6759-c8e5-494e-8833-ec46df0a667b
Potter, Ben
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Edwards, Mary
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Clarke, Charlotte, Monteath, Alistair, Hughes, Paul, Alsos, Inger, Heintzman, Peter, Lammers, Youri, Bigelow, Nancy, Reuther, Joshua, Potter, Ben and Edwards, Mary (2024) Steppe-tundra composition and deglacial floristic turnover in interior Alaska revealed by sedimentary ancient DNA (sedaDNA). Quaternary Science Reviews, 334, [108672]. (doi:10.1016/j.quascirev.2024.108672).

Record type: Article

Abstract

When tracing vegetation dynamics over long timescales, obtaining enough floristic information to gain a detailed understanding of past communities and their transitions can be challenging. The first high-resolution sedimentary DNA (sedaDNA) metabarcoding record from lake sediments in Alaska—reported here—covers nearly 15,000 years of change. It shows in unprecedented detail the composition of late-Pleistocene “steppe-tundra” vegetation of ice-free Alaska, part of an intriguing late-Quaternary “no-analogue” biome, and it covers the subsequent changes that led to the development of modern spruce-dominated boreal forest. The site (Chisholm Lake) lies close to key archaeological sites, and the record throws new light on the landscape and resources available to early humans. Initially, vegetation was dominated by forbs found in modern tundra and/or subarctic steppe vegetation (e.g., Potentilla, Draba, Eritrichium, Anemone patens), and graminoids (e.g., Bromus pumpellianus, Festuca, Calamagrostis, Puccinellia), with Salix the only prominent woody taxon. Predominantly xeric, warm-to-cold habitats are indicated, and we explain the mixed ecological preferences of the fossil assemblages as a topo-mosaic strongly affected by insolation load. At ca. 14,500 cal. yr BP (calendar years before C.E. 1950), about the same time as well documented human arrivals and coincident with an increase in effective moisture, Betula expanded. Graminoids became less abundant, but many open-ground forb taxa persisted. This woody-herbaceous mosaic is compatible with the observed persistence of Pleistocene megafaunal species (animals weighing ≥44 kg)—important resources for early humans. The greatest taxonomic turnover, marking a transition to regional woodland and a further moisture increase, began ca. 11,000 cal. yr BP when Populus expanded, along with new shrub taxa (e.g., Shepherdia, Eleagnus, Rubus, Viburnum). Picea then expanded ca. 9500 cal. yr BP, along with shrub and forb taxa typical of evergreen boreal woodland (e.g., Spiraea, Cornus, Linnaea). We found no evidence for Picea in the late-Pleistocene, however. Most taxa present today were established by ca. 5000 cal. yr BP after almost complete taxonomic turnover since the start of the record (though Larix appeared only at ca. 1500 cal. yr BP). Prominent fluctuations in aquatic communities ca. 14,000 - 9,500 cal. yr BP are probably related to lake-level fluctuations prior to the lake reaching its high, near-modern depth ca. 8,000 cal. yr BP.

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Accepted/In Press date: 17 April 2024
e-pub ahead of print date: 16 May 2024
Published date: 15 June 2024
Additional Information: Publisher Copyright: © 2024 The Authors
Keywords: aquatic macrophytes, diversity, flora, mammalian resources, topoclimate, Flora, Aquatic macrophytes, Diversity, Mammalian resources, Topoclimate

Identifiers

Local EPrints ID: 490670
URI: http://eprints.soton.ac.uk/id/eprint/490670
ISSN: 0277-3791
PURE UUID: d981902a-b140-4d71-8f46-86baadc299da
ORCID for Mary Edwards: ORCID iD orcid.org/0000-0002-3490-6682

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Date deposited: 03 Jun 2024 16:37
Last modified: 18 Jun 2024 01:37

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Contributors

Author: Charlotte Clarke
Author: Alistair Monteath
Author: Paul Hughes
Author: Inger Alsos
Author: Peter Heintzman
Author: Youri Lammers
Author: Nancy Bigelow
Author: Joshua Reuther
Author: Ben Potter
Author: Mary Edwards ORCID iD

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