Interglacial Cycles Research Articles

The Po Plain Loess Basin (Northern Italy): Scientific Values, Threats, and Promotion Opportunities

Geoheritage studies periodically propose assessment methodologies addressed to quantify the value of sites of interests towards geoconservation and/or promotion. Loess outcrops in the Po Plain Loess basin (Northern Italy) represent potential geoheritage sites, allowing to reconstruct glacial and interglacial cycles, testifying evidence of paleoseismicity, and preserving traces of Palaeolithic human exploitation along the foreland of the Alpine and Apennine ranges. In this contribution, firstly we propose a brief review on the loess sites in the framework of geoheritage studies. Then, we evaluate the 6 most significant loess outcrops scattered across the Po Plain Loess Basin (Monte Netto Hill, Val Sorda Sequence, Gajum Section, Ghiardo Plateau, Valenza Section, Torino Hill) applying a quantitative methodology aimed at ranking each locality respect to a benchmark site — the Romanengo Plateau — which is the sole loess site included in the Italian Inventory of Geosites. The 70% of sites obtained a global value higher than our benchmark. They show a high diversity, not only from the scientific point of view (i.e., site-intrinsic geodiversity), but also when we consider their Potential for Use. Despite often disregarded in the international panorama, Italian loess sites require a great attention. Moreover, such sites are evolving passive geomorphosites, thus potentially vulnerable from natural and human causes: this must be considered in the framework of geoconservation and sustainable promotion of each site. Finally, we discuss the possibility of promoting Italian loess sites through different strategies (e.g. virtual tours, 3D models, and gamification based on landscape reconstruction) allowing to visit them by remote and favouring promotion. At the same time, this approach will also promote geoconservation, improving awareness in the general public on the relevance of such sites for Earth (natural and human-related) history.

Eruptive activity of the Santorini Volcano controlled by sea-level rise and fall

Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to interglacial timescales. However, the underlying physical processes and their importance relative to other influences (for example, magma recharge rates) remain poorly understood. Here we compare an approximately 360-kyr-long record of effusive and explosive eruptions from the flooded caldera volcano at Santorini (Greece) with a high-resolution sea-level record spanning the last four glacial–interglacial cycles. Numerical modelling shows that when the sea level falls by 40 m below the present-day level, the induced tensile stresses in the roof of the magma chamber of Santorini trigger dyke injections. As the sea level continues to fall to −70 or −80 m, the induced tensile stress spreads throughout the roof so that some dykes reach the surface to feed eruptions. Similarly, the volcanic activity gradually disappears after the sea level rises above −40 m. Synchronizing Santorini’s stratigraphy with the sea-level record using tephra layers in marine sediment cores shows that 208 out of 211 eruptions (both effusive and explosive) occurred during periods constrained by sea-level falls (below −40 m) and subsequent rises, suggesting a strong absolute sea-level control on the timing of eruptions on Santorini—a result that probably applies to many other volcanic islands around the world.

Late Pleistocene–Holocene pedogenesis and palaeoclimate in western Asia from palaeosols of the Central Iranian Plateau

The Late Pleistocene and Holocene in western Asia is characterized by frequent, millennial‐scale, high‐amplitude environmental climatic changes. However, little is known about palaeoclimate conditions on the arid Central Iranian Plateau and knowledge of palaeosols and past phases of pedogenesis in relation to climatic events is scarce. Nevertheless, these palaeosols contain important information on the Last Glacial–Interglacial cycle and Holocene climate and environmental changes in the region. Three representative pedons with eight argillic horizons from the interior of the Central Iranian Plateau, namely Isfahan, Jimabad and Bajestan are selected for micromorphological, mineralogical and submicroscopic analyses. The ages of these palaeosols are constrained using the optically stimulated luminescence (OSL) signal from quartz. Micromorphological observations show clay illuviation, carbonate leaching, accumulation of secondary carbonates, calcite depletion, and other characteristic pedogenic features. These characteristics, combined with the luminescence chronology, reveal the presence of well‐developed reddish‐brown palaeoargillic horizons (Btk/Btky) with intensive soil formation processes taking place during the Last Interglacial to Middle Holocene (~107–4.5 ka) in our study area. Pedogenic evidence from the palaeosols suggests steps of polygenetic formation in the argillic horizons in response to alternating wetter and drier phases during this period. Four distinct phases of pedogenesis resulting in Btk/Btky horizons are identified: (i) Marine Isotope Stage (MIS) 5, (ii) MIS 3, (iii) the Last Glacial–Interglacial Transition Holocene, and (iv) the Late Holocene.

Genetic History of the Remnant Population of the Rare Orchid Cypripedium calceolus Based on Plastid and Nuclear rDNA.

The lady’s slipper orchid (Cypripedium calceolus), which inhabits shady deciduous and mixed forests and meadows, is now threatened with extinction in many European countries, and its natural populations have been dramatically declining in recent years. Knowledge of its evolutionary history, genetic variability, and processes in small populations are therefore crucial for the species’ protection. Nowadays, in south-west Poland, it is only distributed in seven small remnant and isolated populations, which we examined. One nuclear (ITS rDNA) and two plastid (accD-psa1, trnL-F) markers were analyzed and compared globally in this study. Based on the nuclear marker, the most common ancestor of C. calceolus and Cypripedium shanxiense existed about 2 million years ago (95% HPD: 5.33–0.44) in Asia. The division of the C. calceolus population into the European and Asian lineages indicated by C/T polymorphism started about 0.5 million years ago (95% HPD: 1.8–0.01). The observed variation of plastid DNA, which arose during the Pleistocene glacial–interglacial cycles, is still diffuse in Poland. Its distribution is explained by the result of fragmentation or habitat loss due to human impact on the environment.

Eubuliminella tenuata as a new proxy for quantifying past bottom water oxygenation

In response to modern global warming and climate emergency, large oxygen-depleted oceanic areas, known as Oxygen Minimum Zones (OMZs) have been expanding for the past decades, with negative ecological and economic consequences on food chains, marine ecosystems and resources, biodiversity, and fisheries. The future evolution of these areas and their expansion for the next decades and centuries remain uncertain, and information on their past behaviour during intervals of abrupt climate change (e.g. the last Glacial / Interglacial cycles) is needed to understand the biological and physical mechanisms involved.In this study, a new approach to quantitatively reconstruct past bottom water oxygenation (BWO) was developed, based on the relative abundance of a single benthic foraminiferal species: Eubuliminella exilis (Cushman 1927). A taxonomic review as well as a systematic revision of this taxa, previously assigned to the genus Buliminella Cushman 1911, and synonymised with Eubuliminella exilis (Brady 1884), was also carried out.The method was calibrated using 25 core tops recovered from the Western North Pacific (WNP), the Eastern North Pacific (ENP), the Eastern Equatorial Pacific (EEP), Eastern South Pacific (ESP) and the Arabian Sea (AS) OMZs. It was then applied to five cores from the WNP, and ENP OMZs. Data show a similar and consistent relationship with past [O2] values estimated by using the assemblages method developed in previous studies. We thus propose that the relative abundance of Eubuliminella tenuata (Cushman 1927) could be used as a global proxy for estimating past dissolved oxygenation.

Genome-wide assessment elucidates connectivity and the evolutionary history of the highly dispersive marine invertebrate Littoraria flava (Littorinidae: Gastropoda)

Abstract An important goal of marine population genetics is to understand how spatial connectivity patterns are influenced by historical and evolutionary factors. In this study, we evaluate the demographic history and population structure of Littoraria flava, a highly dispersive marine gastropod in the Brazilian intertidal zone. To test the hypotheses that the species has (1) historically high levels of gene flow on a macrogeographical spatial scale and (2) a distribution in rocky shores that consists of subpopulations, we collected specimens along the Brazilian coastline and combined different sets of genetic markers (mitochondrial DNA, ITS-2 and single nucleotide polymorphisms) with niche-based modelling to predict its palaeodistribution. Low genetic structure was observed, as well as high gene flow over long distances. The demographic analyses suggest that L. flava has had periods of population bottlenecks followed by expansion. According to both palaeodistribution and coalescent simulations, these expansion events occurred during the Pleistocene interglacial cycles (21 kya) and the associated climatic changes were the probable drivers of the distribution of the species. This is the first phylogeographical study of a marine gastropod on the South American coast based on genomic markers associated with niche modelling.

Comparison of the oxygen isotope signatures in speleothem records and iHadCM3 model simulations for the last millennium

Abstract. Improving the understanding of changes in the mean and variability of climate variables as well as their interrelation is crucial for reliable climate change projections. Comparisons between general circulation models and paleoclimate archives using indirect proxies for temperature or precipitation have been used to test and validate the capability of climate models to represent climate changes. The oxygen isotopic ratio δ18O, a proxy for many different climate variables, is routinely measured in speleothem samples at decadal or higher resolution, and single specimens can cover full glacial–interglacial cycles. The calcium carbonate cave deposits are precisely dateable and provide well preserved (semi-)continuous albeit multivariate climate signals in the lower and mid-latitudes, where the measured δ18O in the mineral does not directly represent temperature or precipitation. Therefore, speleothems represent suitable archives to assess climate model abilities to simulate climate variability beyond the timescales covered by meteorological observations (101–102 years). Here, we present three transient isotope-enabled simulations from the Hadley Center Climate Model version 3 (iHadCM3) covering the last millennium (850–1850 CE) and compare them to a large global dataset of speleothem δ18O records from the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database version 2 (Comas-Bru et al., 2020b). We systematically evaluate offsets in mean and variance of simulated δ18O and test for the main climate drivers recorded in δ18O for individual records or regions. The time-mean spatial offsets between the simulated δ18O and the speleothem data are fairly small. However, using robust filters and spectral analysis, we show that the observed archive-based variability of δ18O is lower than simulated by iHadCM3 on decadal and higher on centennial timescales. Most of this difference can likely be attributed to the records' lower temporal resolution and averaging or smoothing processes affecting the δ18O signal, e.g., through soil water residence times. Using cross-correlation analyses at site level and modeled grid-box level, we find evidence for highly variable but generally low signal-to-noise ratios in the proxy data. This points to a high influence of cave-internal processes and regional climate particularities and could suggest low regional representativity of individual sites. Long-range strong positive correlations dominate the speleothem correlation network but are much weaker in the simulation. One reason for this could lie in a lack of long-term internal climate variability in these model simulations, which could be tested by repeating similar comparisons with other isotope-enabled climate models and paleoclimate databases.

Molecular biogeography of the fungus-dwelling saproxylic beetle Bolitophagus reticulatus indicates rapid expansion from glacial refugia

Abstract The geographical distributions of species associated with European temperate broadleaf forests have been significantly influenced by glacial–interglacial cycles. During glacial periods, these species persisted in Mediterranean and extra-Mediterranean refugia and later, during interglacial periods, expanded northwards. The widespread saproxylic beetle Bolitophagus reticulatus depends closely on European temperate broadleaf forests. It usually develops in the tinder fungus Fomes fomentarius, a major decomposer of broadleaf-wood. We sampled B. reticulatus in sporocarps from European beech (Fagus sylvatica) and Oriental beech (Fagus orientalis) across Europe and the Caucasus region. We analysed mitochondrial gene sequences (cox1, cox2, cob) and 17 microsatellites to reconstruct the geographical distribution of glacial refugia and postglacial recolonization pathways. We found only marginal genetic differentiation of B. reticulatus, except for a significant split between populations of the Caucasus region and Europe. This indicates the existence of past refugia south of the Great Caucasus, and a contact zone with European populations in the Crimean region. Further potential refugia might have been located at the foothills of the Pyrenees and in the Balkan region. Our genetic data suggest a phalanx-wise recolonization of Europe, a reflection of the high mobility of B. reticulatus.

Postglacial anthropogenic fires related to cultural changes in central Japan, inferred from sedimentary charcoal records spanning glacial–interglacial cycles

ABSTRACTWe examined long‐term charcoal records spanning the glacial–interglacial cycles that are evident in two cores collected from Lake Biwa in central Japan. We found that the records of the two cores have a similar long‐term variation pattern of charcoal concentrations and abundant large charcoal fragments in postglacial sediments, which indicates that frequent fires occurred near the shores of Lake Biwa during the postglacial period. Analogous natural conditions in the early postglacial period and the early part of the last interglacial period strongly suggest that the frequent fires that occurred only during the postglacial period were anthropogenic. A comparison between the charcoal records of Lake Biwa sediments and the cultural changes and human populations in this district suggests that anthropogenic fires in this district were influenced by the lifestyle and culture of each era rather than by the populations. Humans tended to use more fire at the start of the settlement during the early Neolithic era in this region, in spite of the small population size.

Paleowind directions from the magnetic fabric of loess deposits in the western Chinese Loess Plateau and implications for dust provenance

AbstractThe aeolian loess-paleosol sequences in the Chinese Loess Plateau (CLP) are an excellent archive of variations in atmospheric circulation in the geological past. However, there is no consensus regarding the roles of the East Asian winter monsoon and westerly winds in transporting the dust responsible for loess deposition during glacial and interstadial periods. We conducted detailed measurements of the anisotropy of magnetic susceptibility (AMS) on two parallel loess profiles covering the most recent 130 ka in the western CLP to determine paleowind directions. Results show that the magnetic lineations of the loess and paleosol units in both sections are significantly clustered along the northwest to southeast direction. These observations demonstrate that the prevailing wind system responsible for dust transport in the western CLP was the northwesterly winter monsoon, rather than the westerly winds. The AMS-derived dust-bearing wind direction was relatively stable during the last glacial and interglacial cycle in the western CLP, consistent with sedimentary and AMS evidence from the eastern CLP. Accordingly, it is reasonable to conclude that large areas of deserts and Gobi deserts areas located in the upwind direction were the dominant sources for the aeolian deposits of the Loess Plateau.

Record of Neotectonics and Deep Crustal Fluid Circulation Along the Santa Fe Fault Zone in Travertine Deposits of the Lucero Uplift, New Mexico, USA

AbstractTravertine deposits preserve an invaluable record of both ancient and modern fluid flow. The goal of this study is to reconstruct spatial and temporal patterns in travertine deposition associated with tectonic and climatic controls along the Lucero Uplift in New Mexico, USA. Uranium‐series ages of travertine deposits in the Lucero Uplift range from 0.94 ± 0.01 to 592 ± 110 ka, indicating that travertine formation has been episodically active since at least ∼600 ka. We find minimal evidence to attribute glacial and interglacial cycles to travertine formation in the Lucero Uplift. δ13C values in travertine deposits range from 2‰ to 9‰ (Vienna Pee Dee Belemnite), δ18O values range from 21‰ to 25‰ (Vienna Standard Mean Ocean Water). Positive correlation between travertine δ13C and δ18O values indicate travertine formation is closely associated with various degrees of CO2 degassing. 87Sr/86Sr values in travertine deposits range from 0.714 to 0.717 and (234U/238U)i values exhibit a remarkably wide range from 3.6 to 9.3, indicative of fluid‐rock interaction during deep crustal circulation in more radiogenic basement rocks. Reconstructed δ13C, δ18O, and (234U/238U)i values in the inferred deep fluid sources showed systematic variations with travertine formation ages, while 87Sr/86Sr values remain relatively constant. Based on dating of undeformed travertine deposits, which overlie tilted Santa Fe Group units, and high (234U/238U)i we infer that the Santa Fe fault has not produced a ground‐rupturing earthquake within the last 490 ± 52 to 592 ± 110 ka (2σ). Our study suggest that travertine formation is driven by fluid flow facilitated by tectonic and mantle structures.

Past connections with the mainland structure patterns of insular species richness in a continental-shelf archipelago (Aegean Sea, Greece).

Recent research in island biogeography has highlighted the important role of late Quaternary sea‐level fluctuations in shaping biogeographic patterns in insular systems but focused on oceanic systems. Through this study, we aim investigate how late Quaternary sea‐level fluctuations shaped species richness patterns in continental‐shelf island systems. Focusing on the Aegean archipelago, we first compiled maps of the area's geography using published data, under three sea‐level stands: (a) current; (b) median sea‐level over the last nine glacial–interglacial cycles (MSL); and (c) Last Glacial Maximum (LGM). We gathered taxon–island occurrences for multiple chorotypes of angiosperms, butterflies, centipedes, and reptiles. We investigated the impact of present‐day and past geographic settings on chorological groups by analyzing island species–area relationships (ISARs) and using generalized linear mixed models (GLMMs) selection based on multiple metrics of goodness of fit. Our results confirm that the Aegean's geography has changed dramatically since the LGM, whereas the MSL only modestly differs from the present configuration. Apart for centipedes, paleogeographic changes affected both native and endemic species diversity through altering connections between land‐bridge islands and the mainland. On land‐bridge islands, we detected over‐representation of native species and under‐representation of endemics. Unlike oceanic islands, sea‐level‐driven increase of isolation and area contraction did not strongly shape patterns of species richness. Furthermore, the LGM configurations rather than the MSL configuration shaped patterns of endemic species richness. This suggests that even short episodes of increased connectivity with continental populations are sufficient to counteract the genetic differentiation of insular populations. On the other hand, the over‐representation of native nonendemic species on land‐bridge islands reflected MSL rather than LGM mainland connections. Our study shows that in terms of processes affecting species richness patterns, continental archipelagos differ fundamentally from oceanic systems because episodic connections with the mainland have profound effects on the biota of land‐bridge islands.

Spatiotemporally varying inter-relationships between mainstem riverbed elevation and tributary sediment supply since the last interglacial in the upper Ara River, central Japan

The dynamics of sediment transport processes over millennial time scales in mountain river valleys remain poorly understood, limiting our overall understanding of sediment routing through river basins. Here, we reconstruct changes of the mainstem riverbed elevation, tributary sediment supply processes, and their inter-relationships since the last interglacial in the upper Ara River valley, central Japan. Aggradation of the mainstem river valley began before 100–95 ka and terminated by 41–40 ka. Then, the elevation of the mainstem floodplain remained stable until ~15 ka. Lateral erosion by the mainstem river, and intermittent periods of incision, continued until 5 ka, after which the mainstem river began actively incising. Aggradation of the mainstem riverbed before 41–40 ka elevated tributary junctions, decreasing the slopes of tributaries. Using reconstructed slope changes, and assuming sediment transport by debris flow in tributaries with slopes steeper than 8% and by traction in shallower tributaries, we classified the tributaries into three types: Type-A, with sediment supply by debris flow since the last interglacial; Type-B, with sediment supply by traction during the last glacial period and afterwards by debris flow; and Type-C, with sediment supply by traction since the last interglacial. Based on the relation between relief ratio and drainage area, we subdivided Type-C tributaries into those that plotted along (Type-C1) or markedly below (Type-C2) the regression line of the mainstem river and Type-A and -B tributaries. During aggradation of the mainstem river, sediments supplied by debris flow from Type-A and -B tributaries accumulated around junctions, interfingering with mainstem deposits. During this period, the junctions of Type-C1 tributaries were elevated almost synchronously with mainstem aggradation, while the junctions of Type-C2 tributaries were blocked by mainstem river deposits, forming blocked-valley lakes. Around 30 ka, Type-A and -B tributaries formed fans around their junctions that were subsequently truncated by lateral erosion by the mainstem river during the late glacial period and early Holocene, forming toe-cut terraces. Tributary deposits that had accumulated around the junctions were then reworked while maintaining a dynamic equilibrium state with the mainstem river. We infer that the responses of tributary landforms and sediment supply processes to the changing elevation of the mainstem riverbed during glacial and interglacial cycles varied depending on the drainage area and relief of each tributary. Considering the river basin as a whole, however, tributary deposits stabilized the elevation of the mainstem floodplain.

Records of volcanism and organic carbon isotopic composition (δ13Corg) linked to changes in atmospheric pCO2 and climate during the Pennsylvanian icehouse interval

The late Paleozoic ice age (LPIA) during the Carboniferous and Permian (ca. 360–260 Ma) was vegetated Earth's only recorded icehouse-to-greenhouse transition and provides a deep-time perspective for climate-glaciation-environment coevolution and future climate change. During the LPIA, changes in glacial-interglacial cycles have been closely linked to atmospheric pCO2. In this paper, we investigate the relationship between volcanism and glacial to interglacial climate cycles during the Pennsylvanian to earliest Cisuralian in the Liujiang Coalfield from the North China Plate (NCP). We use integrated data from Zircon U-Pb dating, Hg/TOC ratios and δ13Corg to recover temporal trends in volcanic intensity and relate these to fluctuations in the global carbon cycle and atmospheric pCO2. Four new radiometric dates from tuffaceous claystones provide a precision stratigraphic framework and constrain the succession to ~322 to 301 Ma. Results date the Benxi Formation to the Bashkirian–Moscovian stages of the Carboniferous, and the Taiyuan Formation ranging from the Kasimovian stage of the Carboniferous to the Asselian stage of the Permian. Results from Hg/TOC ratios record four peaks of volcanic intensity from the Bashkirian to the Carboniferous-Permian (C-P) transition period, and two low ebbs during the early-middle Bashkirian and the early-middle Moscovian. Peaks in volcanic intensity coincide with the four negative excursions of δ13Corg and correlate with volcanism in the North China Plate and NW Europe, inferring volcanic drivers for the carbon isotope excursions and perturbations in the global carbon cycle. Periods of higher atmospheric pCO2 correlate to interglacial intervals, the two lower ebbs in pCO2 correlate with two positive isotope plateaus, while periods of lower atmospheric pCO2 and cooling correlate with glacial intervals C3 and C4 recognized from other sections globally. Results suggest volcanism to be a significant driver for late Pennsylvanian to earliest Cisuralian shifts in global climates from glacial to interglacial through greenhouse gas emissions and changes to the global carbon cycle. Our results represent an important contribution to the development of an accurate chronostratigraphy for the continental facies of the NCP during the Pennsylvanian and earliest Permian, enabling correlation of volcanic and climate events including glacial and interglacial cycles.

Regional climates shape the biogeographic history of a broadly distributed freshwater crab species complex

AbstractAimThe evolutionary importance of paleoclimate regimes has been noted in biogeographic studies. However, little is known about how paleoclimate differences shaped the biogeographic pattern and diversification history of the freshwater fauna in important zoogeographical boundary regions. Here, we aim to investigate how past regional climatic differences have shaped the biogeographic history of the inland aquatic fauna in China using an endemic freshwater crab species complex found on both sides of the Qinling Mountains–Huaihe River Line (QHL), a critical ecological boundary in eastern China, as a model system.LocationEastern China, the Qinling Mountains–Huaihe River Line.TaxonThe Sinopotamon yangtsekiense species complex.MethodsA total of 482 individuals of Sinopotamon yangtsekiense sensu lato were collected from 34 localities throughout its entire distributional range. The phylogeographic analyses of population structure, morphological and genetic variations, and demographic dynamics were made based on multiple mtDNA and nuDNA loci and on morphological traits. Fine‐tuned ecological niche modeling was used to reconstruct the location of climatically suitable areas that existed during the Last Glacial Maximum.ResultsThe divergence of two freshwater crab lineages across the QHL correlated with significant past variations in monsoon intensity and with the location of multiple refuges. The divergence time was broadly consistent with the timing of the critical paleoclimate transition event in the mid‐Pleistocene (95% HPD, 0.48–1.06 Ma). Each freshwater crab lineage has evolved distinct male genital traits associated with their isolation in areas with different precipitation rates and temperatures in the past. The patterns of crab distribution observed today reflect past contractions of the two lineages in response to glacial and interglacial cycles during the Pleistocene, followed by their subsequent rapid expansion after the Last Glacial Maximum (~15 kya).Main conclusionsPopulations of the widespread species Sinopotamon yangtsekiense s.l. experienced a deep division in the past that led to the phylogeographical isolation observed today. The two main drivers of genetic isolation in this taxon were (a) differences in the intensity of the monsoons on each side of the QHL boundary during the mid‐Pleistocene, and (b) isolation of different populations of S. yangtsekiense s.l. in a number of separate refuges during the LGM.

Evolutionary history of the oriental fire-bellied toad (Bombina orientalis) in Northeast China.

The evolutionary history of a species is generally affected by the combination of geological events and climate fluctuations. By analyzing the population features, genetic structure and the effective population historical dynamics of existing species, the population evolutionary history can be reestablished. In recent years, geological evidence shows that the Yilan–Yitong fault zone located in Northeast Asia experienced strong and frequent geological changes in the late Quaternary period. Species population history has been shaped by the combination of the complex climatic conditions of the Quaternary and Pleistocene glacial interglacial cycles and palaeogeological events in Northeast Asia and it has become a research focus for evolutionary biology researchers. In this study, mitochondrial and microsatellite molecular markers were used to reveal the population features, genetic structure, and the effective population historical dynamics of the Oriental fire‐bellied toad (Bombina orientalis). The results showed that the strong seismic activity of the Yilan–Yitong fault zone in the late Quaternary period was the main reason for the population differentiation of Oriental fire‐bellied toad in northeast China. The Quaternary Pleistocene glacial interglacial cycles led to the significant bottleneck effect of the western population located in the Maoer mountain area. As a result, the western population has low genetic diversity. Recent gene flow between eastern and western populations and historical evidence of population expansion proved that the dispersal behavior of the western populations was the main cause of the low genetic diversity and mitochondrial and nuclear discordance. Human economic activity may be the mainly driving factor. These evidences showed that the comprehensive influence of geology, climate, human activities and other factors should be considered in the process of exploring the evolutionary history of species.

Out of the Pan‐Himalaya: Evolutionary history of the Paeoniaceae revealed by phylogenomics

AbstractPeonies (the Paeoniaceae, Paeonia L.) are famous garden flowers, medicinal plants, and edible oil crops, but their evolutionary history largely remains unknown. To probe into their phylogenetic relationships, evolutionary history, formation of present distribution pattern, and origins of tetraploids, we sequenced 25 fragments belonging to 20 single copy nuclear genes and 14 chloroplast regions of all species in the genus to reconstruct phylogenetic relationships, date the divergence times of lineages, infer the ancestral biogeographical regions, and document the parents of tetraploids. Our results show that Paeoniaceae separated from the other members in Saxifragales in the Campanian of the late Cretaceous and diverged into two clades, woody and herbaceous clades, in the late Oligocene or early Miocene. They survived and early diverged in the Pan‐Himalaya where they migrated eastwards to East Asia and further to NW America, and northwards to Middle Asia, and further to Europe. The woody lineage differentiated into two sublineages with accelerated root or floral disk evolution, while the herbaceous lineage diverged into five sublineages. Multiple glacial and interglacial cycles in Europe in the late Pliocene and early Pleistocene created opportunities for the peony species to meet and hybridize in the Mediterranean refugia, giving rise to eight allotetraploid species and four infraspecific tetraploids. Paeonia daurica Andrews, P. obovata Maxim., and P. tenuifolia L. served as the most important parents. The phylogeny of Paeonia L. implies that a new taxonomic system with two subgenera and seven sections should be proposed.

The demography of extinction in eastern North American birds.

Species are being lost at an unprecedented rate during the Anthropocene. Progress has been made in clarifying how species traits influence their propensity to go extinct, but the role historical demography plays in species loss or persistence is unclear. In eastern North America, five charismatic landbirds went extinct last century, and the causes of their extinctions have been heavily debated. Although these extinctions are most often attributed to post-colonial human activity, other factors such as declining ancestral populations prior to European colonization could have made these species particularly susceptible. We used population genomic data from these extinct birds and compared them with those from four codistributed extant species. We found extinct species harboured lower genetic diversity and effective population sizes than extant species, but both extinct and non-extinct birds had similar demographic histories of population expansion. These demographic patterns are consistent with population size changes associated with glacial-interglacial cycles. The lack of support for overall population declines during the Pleistocene corroborates the view that, although species that went extinct may have been vulnerable due to low diversity or small population size, their disappearance was driven by human activities in the Anthropocene.

Glacial to interglacial climate variability in the southeastern African subtropics (25–20° S)

Abstract. We present a continuous and well-resolved record of climatic variability for the past 100 000 years from a marine sediment core taken in Delagoa Bight, off southeastern Africa. In addition to providing a sea surface temperature reconstruction for the past ca. 100 000 years, this record also allows a high-resolution continental climatic reconstruction. Climate sensitive organic proxies, like the distribution and isotopic composition of plant-wax lipids as well as elemental indicators of fluvial input and weathering type provide information on climatic changes in the adjacent catchment areas (Incomati, Matola and Lusutfu rivers). At the transition between glacials and interglacials, shifts in vegetation correlate with changes in sea surface temperature in the Agulhas Current. The local hydrology, however, does not follow these orbitally paced shifts. Instead, precipitation patterns follow millennial-scale variations with different forcing mechanisms in glacial vs. interglacial climatic states. During glacials, southward displacement of the Intertropical Convergence Zone facilitates a transmission of northern hemispheric signals (e.g., Heinrich events) to the southern hemispheric subtropics. Furthermore, the southern hemispheric westerlies become a more direct source of precipitation as they shift northward over the study site, especially during Antarctic cold phases. During interglacials, the observed short-term hydrological variability is also a function of Antarctic climate variability; however, it is driven by the indirect influence of the southern hemispheric westerlies and the associated South African high-pressure cell blocking the South Indian Ocean Convergence Zone related precipitation. As a consequence of the interplay of these effects, small-scale climatic zones exist. We propose a conceptual model describing latitudinal shifts of these zones along the southeastern African coast as tropical and temperate climate systems shift over glacial and interglacial cycles. The proposed model explains some of the apparent contradictions between several paleoclimate records in the region.

Sequential changes in ocean circulation and biological export productivity during the last glacial–interglacial cycle: a model–data study

Abstract. We conduct a model–data analysis of the marine carbon cycle to understand and quantify the drivers of atmospheric CO2 concentration during the last glacial–interglacial cycle. We use a carbon cycle box model, “SCP-M”, combined with multiple proxy data for the atmosphere and ocean, to test for variations in ocean circulation and Southern Ocean biological export productivity across marine isotope stages spanning 130 000 years ago to the present. The model is constrained by proxy data associated with a range of environmental conditions including sea surface temperature, salinity, ocean volume, sea-ice cover and shallow-water carbonate production. Model parameters for global ocean circulation, Atlantic meridional overturning circulation and Southern Ocean biological export productivity are optimized in each marine isotope stage against proxy data for atmospheric CO2, δ13C and Δ14C and deep-ocean δ13C, Δ14C and CO32-. Our model–data results suggest that global overturning circulation weakened during Marine Isotope Stage 5d, coincident with a ∼ 25 ppm fall in atmospheric CO2 from the last interglacial period. There was a transient slowdown in Atlantic meridional overturning circulation during Marine Isotope Stage 5b, followed by a more pronounced slowdown and enhanced Southern Ocean biological export productivity during Marine Isotope Stage 4 (∼ −30 ppm). In this model, the Last Glacial Maximum was characterized by relatively weak global ocean and Atlantic meridional overturning circulation and increased Southern Ocean biological export productivity (∼ −20 ppm during MIS 3 and MIS 2). Ocean circulation and Southern Ocean biological export productivity returned to modern values by the Holocene period. The terrestrial biosphere decreased by 385 Pg C in the lead-up to the Last Glacial Maximum, followed by a period of intense regrowth during the last glacial termination and the Holocene (∼ 600 Pg C). Slowing ocean circulation, a colder ocean and to a lesser extent shallow carbonate dissolution contributed ∼ −70 ppm to atmospheric CO2 in the ∼ 100 000-year lead-up to the Last Glacial Maximum, with a further ∼ −15 ppm contributed during the glacial maximum. Our model results also suggest that an increase in Southern Ocean biological export productivity was one of the ingredients required to achieve the Last Glacial Maximum atmospheric CO2 level. We find that the incorporation of glacial–interglacial proxy data into a simple quantitative ocean transport model provides useful insights into the timing of past changes in ocean processes, enhancing our understanding of the carbon cycle during the last glacial–interglacial period.