Beringia Research Articles

Evidence of Ice Age humans in eastern Beringia suggests early migration to North America

Our understanding of the timing and pathway of human arrival to the Americas remains an important and polarizing topic of debate in archaeology and anthropology. Traditional consensus, supported by archaeological and paleoenvironmental data, favors a ‘swift peopling’ of the Americas from Asia via the Bering Land Bridge during the last Glacial termination. More recent genetic data and archaeological finds have challenged this view, proposing the ‘Beringian standstill hypothesis’ (BSH), wherein a population of proto-Americans migrated from Asia during, or even prior to the Last Glacial Maximum (LGM) and lived in Beringia for thousands of years before their eventual spread across the American continents. Using a sediment archive from Lake E5 (68.641667° N, 149.457706° W), located on Alaska's North Slope, we present new data supporting the BSH and shedding new light on the environmental impact of these early American populations. Fecal biomarkers support human presence in the environs of the lake, and our data demonstrate elevated biomass burning in this region during the last Glacial. Elevated burning defies the expectation that natural fires would be less frequent in the Arctic during the last Glacial, thereby suggesting human ignition as the likely culprit. Our data shed new light on the pathway and timing of human migration to the Americas and demonstrate the possibility of the sustainable coexistence of humans and the Ice Age megafauna in Beringia prior to their extinction.

Mechanistic modeling of environmental drivers of woolly mammoth carrying capacity declines on St. Paul Island.

On St. Paul Island, a remnant of the Bering Land Bridge, woolly mammoths persisted until 5,600yr BP with no known predators or competitors, providing a natural system for studying hypothesized environmental drivers of extinction. These include overheating due to rising temperatures, starvation, and drought. Here, we test these hypotheses using Niche Mapper and LPJ-GUESS to mechanistically estimate mammoth metabolic rates and dietary and freshwater requirements and, from these, estimate variations in island carrying capacity on St. Paul for the last 17,000yr. Population carrying capacity may have been several hundred individuals at the time of initial isolation from the mainland. Adult mammoths could have fasted for two to three months, indicating a necessary ability to access snow-buried forage. During the Holocene, vegetation net primary productivity increased, but shrinking island area overrode increased net primary productivity (NPP), lowering carrying capacity to ~100 individuals. NPP and freshwater availability alternated as critical limiting factors for this island population during the environmental changes of the late Pleistocene and Holocene. Only two or three individuals could have been sustained by the freshwater surplus in crater lakes (up to 18 individuals under the most optimistic parameter sensitivity experiments), suggesting that the St. Paul mammoth population was highly dependent on coastal freshwater sources. The simulations are consistent with the available proxy data, while highlighting the need to retrieve new paleohydrological proxy records from the coastal lagoons to test model predictions. More broadly, these findings reinforce the vulnerability of island megaherbivore populations to resource limitation and extinction.

Resolving the Speciation Patterns and Evolutionary History of the Intercontinental Disjunct Genus Corylus (Betulaceae) Using Genome-Wide SNPs.

Understanding the underlying mechanisms of species origin, divergence, and distribution patterns of the intercontinental disjunct taxa has long fascinated botanists. Based on 4,894 genome-wide single-nucleotide polymorphism dataset, we present a molecular phylogenetic reconstruction of genus Corylus (Betulaceae), which have a disjunct distribution between Eurasia and North America (NA). The aim is to explore the speciation patterns and evolutionary relationships of Corylus species by establishing a general phylogenetic framework with extensive sampling. Both the molecular phylogeny inferred from recombination-free dataset and structure analysis support the division of Corylus into four major clades (A–D). Recombination tests and hybridization detection reveal extensive recombination and hybridization events among different clades, which have potentially influenced the speciation process of Corylus. Divergence time estimation indicates that recent common ancestor (MRCA) of Corylus occurred in late Eocene (∼36.38 Ma) and subsequent rapid diversification began during Miocene. Ancestral area reconstruction shows that Corylus originated from southwest China. The arrival of two clades (Clades B and C) to NA was well supported by the long distance dispersal crossing the Bering land bridge. The Himalayas, European-Mediterranean area, and other distribution regions are primarily the recipients of dispersal taxa. Vicariance after dispersal plays an important role in speciation.

Miocene Ulmus fossil fruits from Southwest China and their evolutionary and biogeographic implications

The genus Ulmus L. (Ulmaceae) has a rich Cenozoic fossil record from the Northern Hemisphere, which provides essential information for evolutionary and biogeographic histories. However, compared to its abundant leaf fossils, fruit fossils of Ulmus, which allow accurate identification, are still scarce. In this study, we report two new species of the section Ulmus, Ulmus prelanceaefolia Q.Y. Zhang et Y.W. Xing sp. nov. and U. maguanensis Q.Y. Zhang et Y.W. Xing sp. nov. from the Miocene Huazhige Formation in Wenshan and Maguan basins, southeastern Yunnan, southwestern China. These two species are established based on several well-preserved fossil samaras. Ulmus prelanceaefolia represents the only unequivocal record of the ser. Lanceaefolia in the world and U. maguanensis represents the earliest unequivocal record of the ser. Nitentes in East Asia. The evolutionary and biogeographic histories of Ulmus are discussed by summarizing and revising the fossil fruit records. We deduce that the narrow-winged fruit may be primitive and the two narrow-winged sections, sect. Chaetoptelea and Trichoptelea are the early evolved lineages in Ulmus and have diversified since the Eocene. The Oligocene was an important epoch for the rapid diversification of broad-winged lineages of Ulmus, which was likely due to dispersal advantage in the more open forests originating as the global climate began to cool. We also found frequent exchanges/dispersals and extinction events between or within North America, Asia, and Europe since the Eocene. The North Atlantic and Bering Land Bridges served as important dispersal corridors for Ulmus during the Cenozoic.

Interred with Their DNA

Interred with Their DNA

Continents as Units for the Study of Floristic Assembly and Biodiversity: Focus on North America

Continents as Units for the Study of Floristic Assembly and Biodiversity: Focus on North America

Beryllium-10 chronology of early and late Wisconsinan moraines in the Revelation Mountains, Alaska: Insights into the forcing of Wisconsinan glaciation in Beringia

We present 32 new cosmogenic 10Be exposure ages from a moraine sequence deposited during the Wisconsinan glaciation in the Swift River valley, Revelation Mountains, western Alaska Range. 10Be ages from an early Wisconsinan [Marine Isotope Stage 4] moraine average 59.7 ± 3.6 ka (n = 9; excluding one outlier), and 10Be ages from a late Wisconsinan [Marine Isotope Stage 2] terminal moraine, inboard moraines, and two recessional end moraines average 21.3 ± 0.8 ka (n = 3; excluding two outliers), 20.2 ± 1.0 ka (n = 7; excluding three young outliers), 19.6 ± 1.0 ka (n = 2; excluding one outlier) and 17.7 ± 0.8 ka (n = 4; excluding two outliers), respectively. The early Wisconsinan moraine age coincides with the close of MIS 4, consistent with previous chronologies from Beringia. Whereas Southern Hemisphere glaciers retreated prior to the onset of Heinrich Stadial 6 (64–60 ka), the MIS 4 glacier advance in the Swift River valley terminated at the close of Heinrich Stadial 6, possibly in response to abrupt North Atlantic warming. Our late Wisconsinan ages indicate significant initial glacier retreat between ca. 21.3–17.7 ka (prior to any significant increase in CO2) likely in response to amplified warming from rising insolation. Preservation of MIS 4 moraines in Beringia has traditionally been ascribed to limited MIS 2 glacier advance modulated by low regional moisture availability, stemming from the exposed Bering Land Bridge. However, we hypothesize that atmospheric re-organization forced by the Laurentide Ice Sheet resulted in relatively higher temperatures and drier conditions in Beringia during MIS 2 than MIS 4, allowing for the preservation of early Wisconsinan moraines.

First fossil record of Cedrelospermum (Ulmaceae) from the Qinghai–Tibetan Plateau: Implications for morphological evolution and biogeography

AbstractCedrelospermum Saporta is an extinct genus in the Ulmaceae with abundant fossil records in North America and Europe. However, so far, fossil records of this genus from Asia are sparse, which limits the interpretations of the morphological evolution and biogeographical history of the genus. Here we report well‐preserved fruits (Cedrelospermum tibeticum sp. nov.) and a leaf (Cedrelospermum sp.) of Cedrelospermum from the upper Oligocene Lunpola and Nyima basins in the Qinghai–Tibetan Plateau (QTP). This is the first fossil record of Cedrelospermum in the QTP, showing that this genus grew in this region during the late Oligocene. Cedrelospermum tibeticum fruits are double‐winged, morphologically similar to the Eocene and Oligocene double‐winged Cedrelospermum species from North America. This supports the hypothesis that Cedrelospermum migrated to Asia from North America by way of the Bering Land Bridge. Given that Cedrelospermum was a typical element of Northern Hemispheric flora in the Paleogene and Neogene, the presence of this genus indicates that the central region of the QTP was phytogeographically linked with other parts of the Northern Hemisphere during the late Oligocene. The morphological observations of C. tibeticum fruits and other double‐winged Cedrelospermum fruits suggest an evolutionary trend from obtuse to acute apex for the primary wing. Cedrelospermum tibeticum likely had warm and wet climatic requirements. This type of an environment possibly existed in the central QTP in the late Oligocene, thereby supporting the survival of C. tibeticum.

Temporal and spatial variability in coastline response to declining sea-ice in northwest Alaska

Arctic sea-ice is declining in extent, leaving coastlines exposed to more storm-wave events. There is an urgent need to understand how these changes affect geomorphic processes along Arctic coasts. Here we describe spatial and temporal patterns of shoreline changes along two geomorphologically distinct, storm-wave dominated reaches of the Chukchi Sea coastline over the last 64 years. One study area encompasses the west- to southwest-facing, coarse-clastic shoreline and ice-rich bluffs of Cape Krusenstern (CAKR). The other covers the north-facing, sandy shorelines on barrier islands, ice-rich bluffs, and the Cape Espenberg spit in the Bering Land Bridge National Park (BELA). Both study areas lie within the zone of continuous permafrost, which exists both on and offshore and outcrops as ice-rich bluffs along the BELA coast. We mapped changes in coastal geomorphology over three observation periods: 1950–1980, 1980–2003, and 2003–2014 using aerial and satellite imagery. We then compared these geomorphic changes to changes in sea-ice coverage, which declined ~10 days per decade between 1979 and 2016 in the southern Chukchi Sea. Changes in coastal geomorphology in both BELA and CAKR exhibited high spatial variability over the study period. Between 2003 and 2014, shorelines of barrier islands in BELA exhibited the highest mean rates of change, −1.5 m yr−1, while coarse, clastic barrier beaches in CAKR showed only minimal change. Overall, shorelines in both BELA and CAKR became more dynamic (increasing erosion or increasing accumulation) after ca. 2003, with spatial variability in shoreline changes roughly doubling between the first period of observation (1950–1980) and the last (2003–2014). This increase in coastal dynamism may signal a transitional period leading to new state of geomorphic equilibria along these ice-affected coastlines.

Evolutionary trends in leaf morphology and biogeography of Altingiaceae based on fossil evidence

The extant woody family Altingiaceae, consisting of only one genus Liquidambar L. with ca. 15 species, demonstrates a typical disjunctive distribution among East Asia, North America, and the Mediterranean. However, the fossil record throughout the Cenozoic indicates that Altingiaceae was once widespread in the Northern Hemisphere. After studying the abundant Altingiaceae fossil leaf collections, we revised the easily-confused fossil leaves and corrected the misidentifications. Consequently, we proposed an evolutionary history of Altingiaceae leaf morphology in consulting the modern leaf characteristics. It is revealed that the trilobated leaf morphology is the ancestral character state, whereas both the pentalobated and the undivided, pinnate-veined lineages evolved separately. The latter diverged from the trilobated ancestor in South China in Eocene. The lobed and undivided lineages represent the deciduous and evergreen, respectively. An extensive fossil database of Altingiaceae was built to reconstruct its biogeographical history. We reconfirmed that Altingiaceae developed into a temperate and a subtropical-tropical patterns and migrated across both the Bering and North Atlantic land bridges since Cretaceous, independently. It was widespread in the early Neogene of North America and Eurasia, and became extinct in the high latitude triggered by the global cooling and aridification. The modern disjunctive distribution was finally formed, with southeast Asia as its modern diversity center. This study provides new fossil evidence for understanding the morphology and biogeography of the family Altingiaceae.

Revised phylogeny and historical biogeography of the cosmopolitan aquatic plant genus Typha (Typhaceae)

Typha is a cosmopolitan aquatic plant genus that includes species with widespread distributions. It is a relatively ancient genus with an abundant fossil record dating back to the Paleogene. However, the details of its biogeographic history have remained unclear until now. In this study, we present a revised molecular phylogeny using sequences of seven chloroplast DNA markers from nine species sampled from various regions in order to infer the biogeographic history of the genus. Two clades were recovered with robust support. Typha minima and T. elephantina comprised one clade, and the other clade included the remaining seven species, which represented a polytomy of four robustly supported subclades. Two widespread species, T. angustifolia and T. domingensis, were revealed to be paraphyletic, indicating the need for taxonomic revision. Divergence time estimation suggested that Typha had a mid-Eocene crown origin, and its diversification occurred in the Middle and Late Miocene. Ancestral area reconstruction showed that Typha possibly originated from eastern Eurasia. Both dispersal via the Beringian Land Bridge and recent transoceanic dispersal may have influenced the intercontinental distribution of Typha species.

The first record of Phenacomys (Mammalia, Rodentia, Cricetidae) in Europe (early Pleistocene, Zuurland, The Netherlands)

The Beringian Land Bridge is a well-documented dispersal corridor between the Eurasian continent and North America. Episodic sub-aerial exposure of the land bridge during the Late Cenozoic resulted from climatic oscillations and concomitant lowering of sea level. For much of the Pleistocene, dispersal was predominantly west-to-east (e.g., from Eurasia to North America), but a new discovery of the North American rodent Phenacomys from deeply buried sediments in The Netherlands documents an Early Pleistocene east-to-west invasion. The discovery reinforces earlier suggestive hints of an integrated Holarctic mammal fauna in the Early Pleistocene and provides a unique opportunity to establish a direct correlation of the classic mammal zonations of Europe and North America. Phenacomys is traditionally conceptualized as an endemic North American radiation of voles, and all extant taxa are exclusively North American. The first European remains of Phenacomys were recovered as part of the Zuurland Drilling Project from earliest Pleistocene (ca, 2.3–2.1 Ma) strata. The specimens were found in stratigraphic association with species that are well-known from more southern European assemblages of Early Pleistocene age, but also with contemporaneous taxa traditionally associated with more northern latitudes. The recognition of Phenacomys within the Zuurland assemblage demonstrates that the Bering Land Bridge served as a corridor for dispersal of mammal species during the earliest Pleistocene, and served as a physiographic mechanism for the integration of a circumpolar biogeographic province at that time.

A new terrestrial palaeoenvironmental record from the Bering Land Bridge and context for human dispersal.

Palaeoenvironmental records from the now-submerged Bering Land Bridge (BLB) covering the Last Glacial Maximum (LGM) to the present are needed to document changing environments and connections with the dispersal of humans into North America. Moreover, terrestrially based records of environmental changes are needed in close proximity to the re-establishment of circulation between Pacific and Atlantic Oceans following the end of the last glaciation to test palaeo-climate models for the high latitudes. We present the first terrestrial temperature and hydrologic reconstructions from the LGM to the present from the BLB's south-central margin. We find that the timing of the earliest unequivocal human dispersals into Alaska, based on archaeological evidence, corresponds with a shift to warmer/wetter conditions on the BLB between 14 700 and 13 500 years ago associated with the early Bølling/Allerød interstadial (BA). These environmental changes could have provided the impetus for eastward human dispersal at that time, from Western or central Beringia after a protracted human population standstill. Our data indicate substantial climate-induced environmental changes on the BLB since the LGM, which would potentially have had significant influences on megafaunal and human biogeography in the region.

Post‐glacial East Asian origin of the alpine shrub Phyllodoce aleutica (Ericaceae) in Beringia

AbstractAimThe ice‐free area around the Bering Land Bridge, Beringia, has been noted as an important refugium of organisms preferring cold environments such as arctic‐alpine plants throughout the Pleistocene climate oscillations. Although numerous phylogeographical studies have supported this refugium, recent studies have challenged the idea of a homogeneous refugium in Beringia. We aim to examine a novel scenario of the post‐glacial colonization history of an alpine plant Phyllodoce aleutica in Beringia.LocationThe Japanese Archipelago, the Kamchatka Peninsula, the Aleutian Islands, Alaska.MethodThe range‐wide genetic structure of P. aleutica was elucidated by sequencing 13 nuclear loci. The phylogeographical history was inferred using model‐based approaches based on coalescent simulations together with the potential distributions predicted by ecological niche modelling.ResultsBayesian clustering and phylogenetic networks revealed that P. aleutica was divided into three geographically structured groups: the main island of the Japanese Archipelago, the northern island of the archipelago (Hokkaido) and Beringia, including eastern Hokkaido. The demographic history underlying the genetic structure and the potential distributions at present and during Last Glacial Maximum suggest that their divergence likely predated the last glacial period. Except for genetic admixture with the sister species Phyllodoce glanduliflora, populations in Alaska exhibited lower genetic diversity than those in East Asia and exclusively shared two widespread genotypes. Approximate Bayesian computation showed that a demographic model postulating post‐glacial expansion into Alaska fit better than alternative models.Main conclusionsOur study suggests that P. aleutica in eastern Beringia originated through post‐glacial colonization from East Asia, providing novel insight into the biogeographical history of alpine flora in Beringia.

Phylogeny and biogeography of the pantropical genus Zanthoxylum and its closest relatives in the proto-Rutaceae group (Rutaceae)

Zanthoxylum L. (prickly ash) is the only genus in the Citrus L. family (Rutaceae) with a pantropical distribution. We present the first detailed phylogenetic and biogeographic study of the genus and its close relatives in the proto-Rutaceae group. Our phylogenetic analyses based on two plastid and two nuclear markers show that the genus Toddalia Juss. is nested within Zanthoxylum, that earlier generic and intrageneric classifications need revision, and that the homochlamydeous flowers of the temperate species of Zanthoxylum are the result of a reduction from heterochlamydeous flowers. The biogeographic analyses reveal a Eurasian origin of Zanthoxylum in the Paleocene or Eocene with successive intercontinental or long-range migrations. Zanthoxylum likely crossed the North Atlantic Land Bridges to colonize the Americas in the Eocene, and migrated back to the Old World probably via the Bering Land Bridge in the Oligocene or Miocene. Zanthoxylum also colonized several Pacific Islands and the Hawaiian clade shows phylogenetic incongruence between the plastid and nuclear datasets, suggesting hybridization. The Hawaiian species are one of the rare examples of endemic Hawaiian lineages that are older than the current main islands.

A biogeographic perspective on the evolution of fire syndromes in pine trees (Pinus: Pinaceae).

Our goals were to explore the relationship between biogeography and the evolution of fire-adaptive syndromes in the genus Pinus. We used a previously published time-calibrated phylogeny and conducted ancestral trait reconstruction to estimate the likely timing of diversification in Pinus, and to determine when fire-adaptive syndromes evolved in the lineage. To explore trait conservation among fire syndromes and to investigate historical biogeography, we constructed ancestral state reconstructions using the program RASP and estimated the degree of conservatism for fire-adapted traits in the program BaTS. Our reconstructions suggest that the Bering land bridge, which connected North America and Asia, probably played a major role in early pine evolution. Our estimates indicated that fire-adaptive syndromes seem to have evolved more frequently in New World taxa and probably are related to the uplift of major North American mountain ranges. Our data suggest that certain geographically widespread adaptations to fire evolved repeatedly, possibly due to localized changes in climate and environment, rather than resulting from large dispersal events of pre-adapted individuals.

The world fauna of Synchroidae Lacordaire, 1859 (Coleoptera, Tenebrionoidea, Synchroidae)

Synchroidae Lacordaire, 1859 is a taxonomically and biologically poorly known group. In the present paper, diagnostic characters used to separate genera are analysed and the phylogenetic relationships within this family are preliminarily investigated. Results suggest that the characteristic Synchroa pangu Hsiao, Li, Liu & Pang, 2016 can be removed to establish a new genus, Thescelosynchroa gen. nov. The new combination, T. pangu (Hsiao, Li, Liu & Pang) gen. et comb. nov., is proposed. The definitions of Synchroa Newman, 1838 and Synchroina Fairmaire, 1898 are revised. Moreover, morphological analysis and character comparison also suggest that the familial placement of Mallodrya subaenea Horn, 1888 is questionable. Six species are re-examined and re-diagnosed: Synchroa chinensis Nikitsky, 1999, S. elongatula Nikitsky, 1999, S. formosana Hsiao, 2015, S. melanotoides Lewis, 1895, S. punctata Newman, 1838 and Synchroina tenuipennis Fairmaire, 1898. The male of S. chinensis and the female of S. formosana are described for the first time. Synchroa elongatula and Synchroina tenuipennis are newly recorded from Laos and Indonesia, respectively. We also hypothesize that the Eastern Asian-North American disjunction of Synchroa could be connected to a Mid-Late Tertiary migration of plants via the Bering Land Bridge.

Molecular Phylogeny and Biogeography of Adenocaulon Highlight the Biogeographic Links between New World and Old World

Adenocaulon (Asteraceae) is a small genus with only five species but has a broad amphi-Pacific distribution pattern with three species distributed disjunctly in South America, Central America and North America and two endemic species spanning eastern Asia to the Himalayas. To trace the biogeographic pattern of the genus, we reconstructed its phylogenetic relationships and diversification history based on one nuclear and eight plastid gene regions. Our results showed that Adenocaulon is monophyletic and may have originated in Central America during the Miocene, dispersed into North America and finally reached the Himalayas via the Bering Land Bridge. The hypothesized trajectory implies that long-distance dispersal may have played an important role in the formation of the distribution of this group of species. This hypothesis seems to have gained support from the special morphological structure of fruits of the genus.

The first record of albanerpetontid amphibians (Amphibia: Albanerpetontidae) from East Asia.

Albanerpetontids are an enigmatic fossil amphibian group known from deposits of Middle Jurassic to Pliocene age. The oldest and youngest records are from Europe, but the group appeared in North America in the late Early Cretaceous and radiated there during the Late Cretaceous. Until now, the Asian record has been limited to fragmentary specimens from the Late Cretaceous of Uzbekistan. This led to speculation that albanerpetontids migrated into eastern Asia from North America in the Albian to Cenomanian interval via the Beringian land bridge. However, here we describe albanerpetontid specimens from the Lower Cretaceous Kuwajima Formation of Japan, a record that predates their first known occurrence in North America. One specimen, an association of skull and postcranial bones from a single small individual, permits the diagnosis of a new taxon. High Resolution X-ray Computed Microtomography has revealed previously unrecorded features of albanerpetontid skull morphology in three dimensions, including the presence of a supraoccipital and epipterygoids, neither of which occurs in any known lissamphibian. The placement of this new taxon within the current phylogenetic framework for Albanerpetontidae is complicated by a limited overlap of comparable elements, most notably the non-preservation of the premaxillae in the Japanese taxon. Nonetheless, phylogenetic analysis places the new taxon closer to Albanerpeton than to Anoualerpeton, Celtedens, or Wesserpeton, although Bootstrap support values are weak. The results also question the monophyly of Albanerpeton as currently defined.

Estimating the timescale of Lobaria diversification

AbstractUsing an ITS mutation rate as calibration reference, a three-locus timetree was generated for the genus Lobaria and its most important clades. The timetree resolved most clades with strong support and gave an estimate of the diversification time for Lobaria during the early Oligocene. A fossil impression from a 12–24 million-year-old Miocene deposit is hypothesized here to belong to an ancestral Lobaria species. Additionally, the age estimate indicates that the paleoclimate and the closing or opening of the Bering Strait played a major role in shaping the current distribution of most Lobaria species. It is hypothesized that the Bering land bridge acted as a major highway during warm-temperate climate periods, but as a barrier during Arctic climate times.