Formal subdivision of the Quaternary System/Period: Past, present, and future

Head, Martin J.; Gibbard, Philip L.

doi:10.1016/j.quaint.2015.06.039

Cited by 112 publications

(92 citation statements)

References 152 publications

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“…An early N e drop coincident with the great extinction event at the Cretaceous-Paleogene (K-Pg) boundary was clearly visible, followed by a rapid population expansion. Later N e bottlenecks appeared during Eocene-Oligocene, mid-Miocene, and Pleistocene periods that correspond with other well-known episodes of environmental change 35,36 . The inferred history is largely supported by fossil evidence for Betulaceae 23 .…”

Section: Population History Shows Ancient Bottleneckssupporting

confidence: 56%

Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch

Salojärvi¹,

Smolander²,

Nieminen³

et al. 2017

Nat Genet

246

253

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Forest ecosystems maintain a large share of Northern Hemisphere biodiversity. Boreal forests comprise roughly 30% of global forest area 1 and contain the highest tree density among climate zones 2 . Moreover, boreal regions are undergoing extensive climate change. Annual temperature increases exceeding 1.5 °C are projected to result in a warming of 4-11 °C by the end of this century, with little concomitant increase in precipitation 1 . At this pace, climate zones will shift northward at a greater speed than trees can migrate 3 . To understand how future populations of forest trees may respond to climate change, it is essential to uncover past and present signatures of molecular adaptation in their genomes. Silver birch, B. pendula, is a pioneer species in boreal forests of Eurasia. Flowering of the species can be artificially accelerated 4 , giving it an advantage over other tree species with published genome sequences (such as poplar 5 , spruce 6 , and pine 7 ) for the optimization of fiber and biomass production.Here we sequenced 150 birch individuals and assembled a B. pendula reference genome from a fourth-generation inbred line, resulting in a high-quality assembly of 435 Mb that was linked to chromosomes using a dense genetic map. We analyzed SNPs in the genomes of 80 birch individuals spanning most of the geographic range of B. pendula, as well as seven other members of Betulaceae. Population genomic analyses of these data provide insights into the deep-time evolution of the birch family and on recent natural selection acting on silver birch.Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch Silver birch (Betula pendula) is a pioneer boreal tree that can be induced to flower within 1 year. Its rapid life cycle, small (440-Mb) genome, and advanced germplasm resources make birch an attractive model for forest biotechnology. We assembled and chromosomally anchored the nuclear genome of an inbred B. pendula individual. Gene duplicates from the paleohexaploid event were enriched for transcriptional regulation, whereas tandem duplicates were overrepresented by environmental responses. Population resequencing of 80 individuals showed effective population size crashes at major points of climatic upheaval. Selective sweeps were enriched among polyploid duplicates encoding key developmental and physiological triggering functions, suggesting that local adaptation has tuned the timing of and cross-talk between fundamental plant processes. Variation around the tightlylinked light response genes PHYC and FRS10 correlated with latitude and longitude and temperature, and with precipitation for PHYC. Similar associations characterized the growth-promoting cytokinin response regulator ARR1, and the wood development genes KAK and MED5A.A full list of affiliations appears at the end of the paper.

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Section: Population History Shows Ancient Bottleneckssupporting

confidence: 56%

Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch

Salojärvi¹,

Smolander²,

Nieminen³

et al. 2017

Nat Genet

246

253

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“…(m) NW Madagascar (Anjohibe and Anjokipoty) interval of deposition of Stalagmite ANJB-2 and Stalagmite MAJ-5 (this study). The two vertical dashed lines indicate the boundary of the early, middle, and late Holocene by Walker et al (2012) and Head and Gibbard (2015). in the African locations neighboring Madagascar suggests a roughly consistent wetter and drier climate during the early and middle Holocene, respectively (Fig.…”

Section: Regional Comparisonsmentioning

confidence: 93%

Three distinct Holocene intervals of stalagmite deposition and nondeposition revealed in NW Madagascar, and their paleoclimate implications

et al. 2017

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Abstract. Petrographic features, mineralogy, and stable isotopes from two stalagmites, ANJB-2 and MAJ-5, respectively from Anjohibe and Anjokipoty caves, allow distinction of three intervals of the Holocene in NW Madagascar. The Malagasy early Holocene (between ca. 9.8 and 7.8 ka) and late Holocene (after ca. 1.6 ka) intervals (MEHI and MLHI, respectively) record evidence of stalagmite deposition. The Malagasy middle Holocene interval (MMHI, between ca. 7.8 and 1.6 ka) is marked by a depositional hiatus of ca. 6500 years.Deposition of these stalagmites indicates that the two caves were sufficiently supplied with water to allow stalagmite formation. This suggests that the MEHI and MLHI intervals may have been comparatively wet in NW Madagascar. In contrast, the long-term depositional hiatus during the MMHI implies it was relatively drier than the MEHI and the MLHI.The alternating wet-dry-wet conditions during the Holocene may have been linked to the long-term migrations of the Intertropical Convergence Zone (ITCZ). When the ITCZ's mean position is farther south, NW Madagascar experiences wetter conditions, such as during the MEHI and MLHI, and when it moves north, NW Madagascar climate becomes drier, such as during the MMHI. A similar wetdry-wet succession during the Holocene has been reported in neighboring locations, such as southeastern Africa. Beyond these three subdivisions, the records also suggest wet conditions around the cold 8.2 ka event, suggesting a causal relationship. However, additional Southern Hemisphere highresolution data will be needed to confirm this.

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“…It was introduced during the Second International Geological Congress (IGC) in Bologna (1882), and a "Holocenian" Stage was subsequently proposed by the Portuguese Committee for the Third IGC in Berlin in 1885. The Holocene is now officially defined as a series/epoch within the Quaternary System/Period and was formally ratified by the IUGS in 2008 (Gibbard et al, 2010;Head and Gibbard, 2015;Walker et al, 2008Walker et al, , 2009.…”

Section: The Holocene Series/epochmentioning

confidence: 99%

Subdividing the Holocene Series/Epoch: formalization of stages/ages and subseries/subepochs, and designation of GSSPs and auxiliary stratotypes

Walker

Head

Lowe

et al. 2019

J Quaternary Science

Self Cite

169

104

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The Holocene, which currently spans ~11 700 years, is the shortest series/epoch within the geological time scale (GTS), yet it contains a rich archive of evidence in stratigraphical contexts that are frequently continuous and often preserved at high levels of resolution. On 14 June 2018, the Executive Committee of the International Union of Geological Sciences formally ratified a proposal to subdivide the Holocene into three stages/ages, along with their equivalent subseries/subepochs, each anchored by a Global boundary Stratotype Section and Point (GSSP). The new stages are the Greenlandian (Lower/Early Holocene Subseries/Subepoch) with its GSSP in the Greenland NGRIP2 ice core and dated at 11 700 a b2k (before 2000 CE); the Northgrippian (Middle Holocene Subseries/Subepoch) with its GSSP in the Greenland NGRIP1 ice core and dated at 8236 a b2k; and the Meghalayan (Upper/Late Holocene Subseries/Subepoch) with its GSSP in a speleothem from Mawmluh Cave, north‐eastern India, with a date of 4250 a b2k. We explain the nomenclature of the new divisions, describe the procedures involved in the ratification process, designate auxiliary stratotypes to support the GSSPs and consider the implications of the subdivision for defining the Anthropocene as a new unit within the GTS.

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Formal subdivision of the Quaternary System/Period: Past, present, and future

Cited by 112 publications

References 152 publications

Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch

Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch

Three distinct Holocene intervals of stalagmite deposition and nondeposition revealed in NW Madagascar, and their paleoclimate implications

Subdividing the Holocene Series/Epoch: formalization of stages/ages and subseries/subepochs, and designation of GSSPs and auxiliary stratotypes

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