Interglacial Climate Change Research Articles

Diversification in birds is promoted by plant diversity, topographic heterogeneity and stable paleoclimate

AbstractAimsLong‐term climate stability, contemporary climate and environmental heterogeneity have been linked to bird diversity patterns through their direct impacts on diversification rate, as well as through their indirect effects on plant species richness, which could also directly and indirectly affect bird diversity. This study aimed to quantitatively assess whether these potential drivers could indirectly affect bird species richness through their direct effects on the diversification rate in birds in eastern Asia.LocationMainland China.TaxonBirds.MethodsUsing the distribution data of 1127 bird species across 320 prefecture cities in China and a phylogenetic tree of these bird species, we analysed the distribution patterns of bird species richness and diversification rate of all birds, passerine birds and non‐passerine birds, respectively. We also investigated their relationships with long‐term climate stability, contemporary climate, elevation range and plant diversity using ordinary least squares regression model and simultaneous autoregressive model. In addition, structural equation model was used to analyse whether these drivers could indirectly affect bird species richness through their direct effects on bird diversification rate.ResultsThe results showed that bird species richness and diversification rate were highest in southwestern China. Additionally, diversification rate for passerine birds was higher than non‐passerine birds and all birds. Regression analyses revealed that plant species richness was the variable most associated with bird species richness and diversification rate across the three groups. Notably, results from structural equation model indicated that plant species richness, elevation range and glacial–interglacial climate change can indirectly influence bird species richness by directly affecting diversification rates.Main ConclusionsThese findings emphasize the importance of considering diversification rate when understanding the geographic distribution patterns of bird diversity. The direct and indirect effects of plant species richness, elevation range and glacial–interglacial climate change on bird diversity highlight the crucial role of mountain regions with higher plant diversity and stable paleoclimate in forming and maintaining biodiversity.

Nitrogen isotope homogenization of dissolved ammonium with depth and 15N enrichment of ammonium during incorporation into expandable layer silicates in organic-rich marine sediment from Guaymas Basin, Gulf of California

Sedimentary nitrogen isotopic ratios are used as a proxy for ancient biogeochemical cycles on Earth's surface. It is generally accepted that sediment hole tops record primary signatures because organic nitrogen (ON) is predominant in this part of the hole. In contrast to such early to middle diagenetic stages, it is well known that heavier nitrogen isotope 15N tends to enrich in sedimentary rocks during later diagenetic and metamorphic stages. However, there are some critical gaps in our understanding of nitrogen isotopic alteration associated with abiotic processes during early-middle diagenesis. In this study, we examined the isotope ratios of ammonium nitrogen in interstitial water (IW) and total nitrogen (TN), including exchangeable ammonium and mineral nitrogen, in the solid-phase of organic-rich-sediment recovered by International Ocean Discovery Program (IODP) Expedition 385 cores drilled in the Guaymas Basin, Gulf of California, that contained ammonium-rich IW. The isotopic ratios (δ15N value) of TN are the most variable with depth compared to any other type of nitrogen. This variation can be interpreted as reflecting changes in the water mass environment in the basin caused by glacial–interglacial climate changes, modifying the δ15N values of the marine primary producers. Thus, the δ15N value of TN is a proxy for environmental change in the basin, while each component of TN shows different trends. The δ15N values of IW and exchangeable ammonium did not exhibit significant changes with depth, but the latter values are about 3 ‰ enriched in 15N. This may be due to advective transport of solute into adjacent layers followed by the formation of an isotopic equilibrium between IW and exchangeable ammonium in the case of fast sediment accumulation rate. The δ15N value of exchangeable ammonium is the highest among the other types of nitrogen with one exception, where the δ15N value of TN is the highest. The calculated δ15N values of ON based on mass balance are almost the same as those of associated TN in the shallow sediment layers (< 150 m below seafloor), but the difference in the δ15N values of TN and ON are significant in the deeper layers, where proportions of ON contents are <50%. In particular, in the layer where the δ15N value of TN is the highest, that of ON shows an even higher value and the difference reaches 3.5 ‰. The δ15N values of mineral nitrogen are similar to that of IW ammonium except the surface layers. Under such conditions, when δ15N value of TN is intermediate between those of mineral nitrogen and exchangeable ammonium, calculated δ15N value of ON is close to that of TN. On the other hand, if δ15N value of TN is out of the range between mineral nitrogen and exchangeable ammonium, it causes further difference in δ15N value of ON. It means that the fluctuation of δ15N values of TN is reduced relative to those of ON through depth. It has been considered that δ15N value of TN in sediment is similar to that of ON, and changes in the δ15N value of TN due to diagenesis are limited, but in such environment ON fluctuations over depth may be slightly underestimated.

Orbital global change drove fluvial aggradation and incision in Tibetan upper Mekong river: Chronological perspectives

The Tibetan Plateau (TP), often known as the “Asia Water Tower”, is the source region of several continental-scale rivers. However, due to the extremely difficult access and harsh living conditions in the interior plateau, fluvial processes in the headwaters of these large rivers and their connections to global climate changes remain unknown. In this study, the luminescence (using both quartz and K-feldspar) and AMS 14C dating techniques were employed to date the four terraces of the Zado Basin in order to elucidate the aggradation and incision history of the initial intermontane basin in the headwater of the Mekong River. One sample from the upper part of T4 terrace (which features a 12 m thick gravel layer, the base of which is unexposed) provides a K-feldspar pIR50IR225 age of 125 ± 10 ka, indicating that the initial deposition of this terrace could predate marine isotope stage (MIS) 5. Considering the margin of error, this age also suggests that the onset of incision on T4 terrace during the climate transition from MIS 6 (glacial) to early MIS 5 (interglacial). This incision likely occurred due to increased meltwater and precipitation, causing the Mekong carving into the bedrock for more than 50 m. Eight luminescence samples are collected from T3 terrace (26.5 m in thickness) with ages ranging from 83 ± 7.6 ka to 22.3 ± 1 0.2 ka, indicating T3 formation/aggradation from late MIS 5 to the Last Glacial Maximum (LGM), possibly owing to reduced precipitation and enhanced sediment supply from intensive glacial activities. At around 22 ka, the Mekong once again shifted towards incision, crafting the T3 terrace, situated roughly 28 m above the current floodplain. This incision event was recorded by two luminescence samples from a sandy lens located at the top of gravel layer of T3, with OSL ages of about 22 ka. Floodplain samples from T2 and T1, dated at 16 ka and 2.8 ka respectively, demonstrate that from the last deglaciation to the Holocene, the Mekong continued its downward incision. This erosion developed two cut and fill terraces at elevations of 22 m and 11 m above the present floodplain, likely due to increased precipitation and enhanced vegetation at that time. Overall, the glacial–interglacial climate changes were the most likely driving force behind fluvial processes in the upper Mekong basin since the Late Pleistocene, with aggradation occurring during the glacial period while incision in deglacial and interglacial periods, suggesting a close link between the fluvial geomorphic evolution and orbital-scale climate changes.

Re‐investigation of the Bispingen palaeolake sediment succession (northern Germany) reveals that the Last Interglacial (Eemian) in northern‐central Europe lasted at least ~15 000 years

Investigating past interglacial climatic and environmental changes can enhance our understanding of the natural rates and ranges of climate variability under interglacial boundary conditions. However, comparing past interglacial palaeoclimate records from different regions and archives is often complicated by differing and uncertain chronologies. For instance, the duration of the Last Interglacial in Europe is still controversial as southern European palaeoclimate records suggest a duration of ~16 500–18 000 years, while a length of only ~11 000 years in northern‐central Europe was previously inferred from the analysis of partly annually laminated (varved) palaeolake sediments recovered at Bispingen, northern Germany. To resolve this discrepancy, we here present sediment microfacies, geochemistry and pollen data from a new sediment core from the Bispingen palaeolake sediment succession, covering the entire Last Interglacial (Eemian) and the earliest part of the Last Glacial (Weichselian). In particular, we provide evidence that the duration of the Last Interglacial at Bispingen must have been hitherto underestimated due to the investigation of an incomplete sediment core. Using microscopic varve counting and sedimentation rate estimates for non‐varved sections on the new sediment core, we show that the Eemian in northern‐central Europe probably lasted at least ~15 000 years, about 4000 years longer than previously thought. This new duration estimate is in much better agreement with results from southern European palaeoclimate records, clarifying the enigma of a steep trans‐European vegetation gradient for several millennia at the end of the Last Interglacial.

Geometry of the Meridional Overturning Circulation at the Last Glacial Maximum

Abstract Understanding the contribution of ocean circulation to glacial–interglacial climate change is a major focus of paleoceanography. Specifically, many have tried to determine whether the volumes and depths of Antarctic- and North Atlantic–sourced waters in the deep ocean changed at the Last Glacial Maximum (LGM; ∼22–18 kyr BP) when atmospheric pCO2 concentrations were 100 ppm lower than the preindustrial. Measurements of sedimentary geochemical proxies are the primary way that these deep ocean structural changes have been reconstructed. However, the main proxies used to reconstruct LGM Atlantic water mass geometry provide conflicting results as to whether North Atlantic–sourced waters shoaled during the LGM. Despite this, a number of idealized modeling studies have been advanced to describe the physical processes resulting in shoaled North Atlantic waters. This paper aims to critically assess the approaches used to determine LGM Atlantic circulation geometry and lay out best practices for future work. We first compile existing proxy data and paleoclimate model output to deduce the processes responsible for setting the ocean distributions of geochemical proxies in the LGM Atlantic Ocean. We highlight how small-scale mixing processes in the ocean interior can decouple tracer distributions from the large-scale circulation, complicating the straightforward interpretation of geochemical tracers as proxies for water mass structure. Finally, we outline promising paths toward ascertaining the LGM circulation structure more clearly and deeply.

Stable persistence of relict populations involved evolutionary shifts of reproductive characters in the genus Tanakaea (Saxifragaceae)

AbstractTertiary relicts often show evolutionary stasis in morphology and ecology and have been hypothesized to retain stable population sizes in refugia. However, recent studies have reported that some relicts evolutionarily shifted their physiology, ecology, and morphology and experienced various patterns of demography. To understand the historical survival of relict plants, a multidimensional study investigating the evolution of ecological and morphological traits as well as population demographic history is needed. The genus Tanakaea (Saxifragaceae) comprises two species in China and Japan. These species share most vegetative characteristics and are sometimes treated as a single species. The distribution pattern is relictual, as the populations are confined to small areas in mesic warm temperate forests less influenced by Quaternary glacial climates. Focusing on the relictual plant group, this study tested the hypotheses of evolutionary stasis and population stability in long‐term refugia. Genetic analyses using plastome sequences and genome‐wide single‐nucleotide polymorphisms revealed divergence of the two species approximately 6.8 million years ago and strong genetic differentiation of the regional populations. Demographic analysis revealed that almost all populations retained stable population sizes during glacial–interglacial climate changes, supporting the traditional view. However, morphological assessments revealed a simultaneous shift in breeding systems (from hermaphrodite to dioecy/non‐clonal to clonal reproduction) in Japanese species and intraspecific differentiation of leaf traits. Therefore, the relict species do not show evolutionary stasis in every aspect. Changes in reproductive characteristics may have contributed to their long‐term in situ survival.

Luminescence chronology of loess-palaeosol deposits in the Central Shandong Mountains region: Provenances and paleoclimate implications

The loess-palaeosol deposits of the Central Shandong Mountains (CSM) to the east of the Chinese Loess Plateau (CLP) potentially provide valuable archives for the reconstruction of East Asian monsoon patterns. However, compared to the abundant attention given to the loess layer, fewer studies have explored the palaeosols documenting the processes and characteristics of interglacial climate changes. The high-resolution chronologies and provenances of the palaeosol in the CSM area are still unclear. In this work, the luminescence ages and paleoclimate proxies in the Shaozhuang (SZ) and Focun (FC) sections were studied, by combining detrital zircons U–Pb ages from the loess-palaesosol in Jingbian, Licheng, Focun, Pianguan and Dongming Yellow River sediments. Quartz single-aliquot regenerative dose protocol (SAR) and K-feldspar post-infrared IRSL (pIRIR 290 ) dating results were obtained in the SZ (8.0 ± 1.1 ka −50.8 ± 2.7 ka) and FC (3.8 ± 0.3 ka—144.0 ± 7.8 ka) sections to develop the most detailed CSM region chronologies to date. The analyzed grain sizes and detrital zircon U–Pb ages suggest that the provenance of the CSM loess was dominated by local Yellow River sediments. The palaeosols observed in the field in these two sections were composed of both aggradation soils deposited in the interglacial period and non-aggradation soil formed by the weathering and leaching of the underlying loess. We found evidences for the presence of non-aggradation soils as indicated the relatively high 5–16 μm particle percentages, relatively low chemical index of alteration (CIA) values and the percentages of >63 μm particles compared to those of the overlying palaeosol layers. Nevertheless, the loess-palaeosol deposits in the CSM are still the product of the East Asian monsoon and global climatic variations, as the deposits have recorded the glacial-interglacial cycles.

Climate influence on zinc isotope variations in a loess–paleosol sequence of the Chinese Loess Plateau

Zinc (Zn) is an essential micronutrient, and its isotopes are increasingly applied to understand trace metal biogeochemical cycling. Atmospheric deposition from anthropogenic or natural origins can perturbate the nutrient supply globally. However, our understanding on Zn isotope variations in natural mineral dust and during dust–climate interaction is still rare. This study presents Zn isotope data and leaching experiments with ammonium acetate buffering solution (pH = 5) on a loess–paleosol profile (S0–L3) from the Yimaguan section in the central Chinese Loess Plateau. The loess–paleosol sequence records the contributions from Asian mineral dust accumulation and chemical weathering, and the response to glacial–interglacial climate changes. Bulk loess–paleosol samples display limited Zn/Al (3.5 × 10-4 – 4.5 × 10-4) and δ66Zn variations (0.17–0.30‰). The mean δ66Zn of paleosol (0.19 ± 0.01‰, 2SD/√n, n = 11) is slightly lower than that of loess (0.24 ± 0.01‰, 2SD/√n, n = 13). Correlations with magnetic susceptibility and grain size distribution suggest that bulk δ66Zn variations between loess and paleosol are not sensitive to glacial–interglacial source fluctuations or wind sorting, but could result from loess pedogenesis.The leachable Zn fractions have high δ66Zn values (0.80–1.29‰) and display good positive correlations with Ca, Sr, Mg, Fe and Mn (r > 0.7), suggesting that carbonates are enriched in heavy Zn isotopes. Although Zn contents in carbonates are low (<3%) and dissolution of carbonates alone cannot explain the bulk Zn/Al variations (∼7% of Zn loss), significant carbonate weathering and biotic activities during loess pedogenesis could modify soil conditions (pH) and provide dissolved bicarbonate ions and organic ligands, which may facilitate the transport of heavy Zn isotopes by soil liquids. Conversely, the bulk δ66Zn of loess developed during glacial times were not modified by the low degree of chemical weathering, and thus the mean value of 0.24‰ for loess can be regarded as the average composition of the upper continental crust.

Thermal niches of planktonic foraminifera are static throughout glacial–interglacial climate change

Abiotic niche lability reduces extinction risk by allowing species to adapt to changing environmental conditions in situ. In contrast, species with static niches must keep pace with the velocity of climate change as they track suitable habitat. The rate and frequency of niche lability have been studied on human timescales (months to decades) and geological timescales (millions of years), but lability on intermediate timescales (millennia) remains largely uninvestigated. Here, we quantified abiotic niche lability at 8-ka resolution across the last 700 ka of glacial-interglacial climate fluctuations, using the exceptionally well-known fossil record of planktonic foraminifera coupled with Atmosphere-Ocean Global Climate Model reconstructions of paleoclimate. We tracked foraminiferal niches through time along the univariate axis of mean annual temperature, measured both at the sea surface and at species' depth habitats. Species' temperature preferences were uncoupled from the global temperature regime, undermining a hypothesis of local adaptation to changing environmental conditions. Furthermore, intraspecific niches were equally similar through time, regardless of climate change magnitude on short timescales (8 ka) and across contrasts of glacial and interglacial extremes. Evolutionary trait models fitted to time series of occupied temperature values supported widespread niche stasis above randomly wandering or directional change. Ecotype explained little variation in species-level differences in niche lability after accounting for evolutionary relatedness. Together, these results suggest that warming and ocean acidification over the next hundreds to thousands of years could redistribute and reduce populations of foraminifera and other calcifying plankton, which are primary components of marine food webs and biogeochemical cycles.

The Effects of Multi-Scale Climate Variability on Biodiversity Patterns of Chinese Evergreen Broad-Leaved Woody Plants: Growth Form Matters

Large-scale patterns of species diversity are thought to be linked to contemporary climate variability and Quaternary glacial–interglacial climate change. For plants, growth forms integrate traits related to competition or migration capacity, which determine their abilities to deal with the climate variability they face. Evergreen broad-leaved woody plants (EBWPs) are major components of numerous biomes in the subtropical and tropical regions. Hence, incorporating phylogenetic (temporal) and biogeographic (spatial) approaches, we assessed the relative importance of short- and long-term climate variability for biodiversity patterns of different growth forms (i.e., tree, shrub, liana, and bamboo) in EBWPs. We used a dated phylogeny and the distribution records for 6,265 EBWP species which are naturally occurred in China, and computed the corrected weighted endemism, standardized phylogenetic diversity and net relatedness index for the four growth forms, respectively. Ordinary least squares linear regressions, spatial error simultaneous autoregressive models, partial regression and hierarchical variation partitioning were employed to estimate the explanatory power of contemporary climate variability and climate-change velocity from the Last Glacial Maximum to the present. Our results showed that short- and long-term climate variability play complementary role in the biogeographic patterns of Chinese EBWPs. The former had larger effects, but the legacy effects of past climate changes were also remarkable. There were also differences in the effects of historical and current climate among the four growth forms, which support growth forms as a critical plant trait in predicting vegetation response to climate change. Compared to the glacial-interglacial climate fluctuation, seasonality as a unique feature of mid-latitude monsoon climate played a dominant role in the diversification and distribution of EBWP species at the macroscale. The results indicated that the relative importance of climate variability at different temporal scales may relate to distinct mechanisms. To understand effects of future climate change on species distribution more thoroughly, climate conditions in different time scales should be incorporated.

Asian inland wildfires driven by glacial–interglacial climate change

Wildfire can influence climate directly and indirectly, but little is known about the relationships between wildfire and climate during the Quaternary, especially how wildfire patterns varied over glacial-interglacial cycles. Here, we present a high-resolution soot record from the Chinese Loess Plateau; this is a record of large-scale, high-intensity fires over the past 2.6 My. We observed a unique and distinct glacial-interglacial cyclicity of soot over the entire Quaternary Period synchronous with marine δ18O and dust records, which suggests that ice-volume-modulated aridity controlled wildfire occurrences, soot production, and dust fluxes in central Asia. The high-intensity fires were also found to be anticorrelated with global atmospheric CO2 records over the past eight glacial-interglacial cycles, implying a possible connection between the fires, dust, and climate mediated through the iron cycle. The significance of this hypothetical connection remains to be determined, but the relationships revealed in this study hint at the potential importance of wildfire for the global climate system.

Climate change and biogeographic connectivity across the Brazilian cerrado

AbstractAimTo investigate cerrado responses to glacial–interglacial climate change and the potential for connective rain forest corridors between the Atlantic Coastal Forest and Amazonian rain forest.LocationThe crater lake of Serra Negra (18 °S, 46 °W) in Minas Gerais, Brazil.Taxon117 fossil pollen types, 22 non‐pollen palynomorphs were documented.MethodsWe recovered 7.82 m of sediment from the lake, and analysed fossil pollen at 62 depth intervals throughout the core. We derived a chronology based on radiocarbon dating with simple rate extrapolation to the base of the core.ResultsThe c. 90,000‐year fossil record showed a trend towards cooler climates at the Last Glacial Maximum (LGM), but interstadial warming coupled with reduced evaporative stress allowed the expansion of woodlands under cool, moist conditions. Cool‐adapted trees were most abundant between c. 67,000 and 48,000 years ago. A cool cerrado‐like environment marked full glacial conditions between c. 48,000 and 34,000 years ago. The peak of the LGM between c. 34,000 and 17,000 years ago is inferred to have been dry as no sediment accumulated in the system.Main conclusionsExpanded ranges of cold‐tolerant forest taxa led to establishment of a series of assemblages without modern analogue. A system characteristic of modern cerrado was rare in the history of this site. Multiple forest expansions were observed, each differing in composition. The periods of forest abundance at Serra Negra were not temporally aligned with forest expansion in the Atlantic Coastal Forest, and did not provide a continuous corridor of similar forest that connected the cerrado to the Atlantic Coastal Forest.

Species and phylogenetic endemism in angiosperm trees across the Northern Hemisphere are jointly shaped by modern climate and glacial–interglacial climate change

AbstractAimsPhylogenetic endemism describes the extent to which unique phylogenetic lineages are constrained to restricted geographic areas. Previous studies indicate that species endemism is related to both past and modern climate, but studies of phylogenetic endemism are relatively rare and mainly focused on smaller regions. Here, we provide the first assessment of the patterns of species and phylogenetic endemism in angiosperm trees across the Northern Hemisphere as well as the relative importance of modern climate and glacial–interglacial climate change as drivers of these patterns.LocationNorthern Hemisphere.Major taxaAngiosperm trees.MethodsUsing tree assemblages at the scale of 100 km × 100 km grid cells and simultaneous autoregressive (SAR) models, we assessed the relationships between species endemism, phylogenetic endemism and modern climate variables, Last Glacial Maximum (LGM) to present temperature velocity.ResultsSpecies and phylogenetic endemism were associated with both modern climate and glacial–interglacial climate change, with higher values in areas with stable historical climate and warmer and wetter modern conditions. Notably, the multivariate SAR analyses showed that the combinations of variables with highest Akaike’s information criterion (AIC) weight always included both LGM–present climate instability and modern climate, that is, modern precipitation and temperature.Main conclusionsOur results show that high phylogenetic endemism is partially dependent on long‐term climate stability, highlighting the threat posed by future climate changes to the preservation of rare, phylogenetically distinct lineages of trees.

Changes in the Asian monsoon climate during the late last interglacial recorded in oxygen isotopes of a stalagmite from the Yongxing Cave, central China

The last interglacial contains information about how climate behaves during a warm period comparable to the current interval. However, there is no consensus on the key signatures and force of the last interglacial climate changes at present. Here we present a high-resolution stalagmite oxygen isotope record from central China, which spans from 123.3 to 116.8 ka. The stalagmite δ18O time-series bears a resemblance to changes in Northern Hemisphere summer insolation before the demise of the last interglacial, like the condition during the Holocene. Superimposed on the long-term δ18O record is a pronounced shift to more positive values at around 121.6 ka, indicating a switch of the Asian monsoon mean state into a weaker condition. This monsoon shift correlates with a decrease in the mean state of the South American Summer Monsoon, and a well-known abrupt mid-Eemian cooling event at high latitudes. These correlations indicate broad-scale features of the climate shift over the warm last interglacial. Another positive δ18O shift of up to 3.5‰ occurred at around 120 ka, representing the demise of the last interglacial Asian monsoon. By comparing the stalagmite δ18O records against changes in ice volume and summer insolation during the last interglacial and recent Holocene, respectively, we conclude that the decreasing Northern Hemisphere summer insolation dominated the rapid demise of the last interglacial in the Asian monsoon region.

Contrasting phylogeographic histories between the continent and islands of East Asia: Massive mitochondrial introgression and long-term isolation of hares (Lagomorpha: Lepus)

Hares of the genus Lepus are distributed worldwide, and introgressive hybridization is thought to be pervasive among species, leading to reticulate evolution and taxonomic confusion. Here, we performed phylogeographic analyses of the following species of hare across East Asia: L. timidus, L. mandshuricus, L. coreanus, and L. brachyurus collected from far-eastern Russia, South Korea, and Japan. Nucleotide sequences of one mitochondrial DNA and eight nuclear gene loci were examined, adding sequences of hares in China from databases. All nuclear DNA analyses supported the clear separation of three phylogroups: L. timidus, L. brachyurus, and the L. mandshuricus complex containing L. coreanus. On the other hand, massive mitochondrial introgression from two L. timidus lineages to the L. mandshuricus complex was suggested in continental East Asia. The northern population of the L. mandshuricus complex was mainly associated with introgression from the continental lineage of L. timidus, possibly since the last glacial period, whereas the southern population of the L. mandshuricus complex experienced introgression from another L. timidus lineage related to the Hokkaido population, possibly before the last glacial period. In contrast to continental hares, no evidence of introgression was found in L. brachyurus in the Japanese Archipelago, which showed the oldest divergence amongst East Asian hare lineages. Our findings suggest that glacial–interglacial climate changes in the circum-Japan Sea region promoted distribution shifts and introgressive hybridization among continental hare species, while the geographic structure of the region contributed to long-term isolation of hares on the islands, preventing inter-species gene flow.

Impact of the last interglacial climate change on ecosystems and Neanderthals behavior at Baume Moula-Guercy, Ardèche, France

Earth's climate experienced a major warming during the last interglacial period (Eemian, MIS 5e, LIG 128 to 114 ky). The rapid climate change altered ecosystems causing a geographical redistribution of flora and fauna. Due to the scarcity of archaeological sites representing this period, the effect of these events on the behavior of Neanderthal hunter-gatherers in Western Europe has been poorly understood. New evidence from a wellpreserved archaeological layer (XV) at Baume (cave) Moula-Guercy in Southeastern France, attributed to the optimum Eemian Interglacial, unparalleled on the European continent, allows us to consider the challenges Neanderthals faced as these new ecosystems and ecological communities formed. We argue that, on the European continent, the human population collapsed, maintaining itself only in a few regions. We further suggest that these environmental upheavals, including depletion of prey biomass at the beginning of the Upper Pleistocene, contributed to the rise of cannibalistic behavior in Neanderthals, as exhibited among remains found at the Baume Moula-Guercy.

High resolution 14C AMS ages (∼50 ka) of organic matter associated with the loess-palaeosol Holocene-Late Pleistocene (8–130 ka) sediments of Dilpur Formation, Karewa Group, Kashmir, India

Abstract High resolution 14C AMS ages from sequential layers in the late Quaternary Dilpur Formation in Indian Kashmir, reveal glacial and inter-glacial climatic changes archived in this more or less complete aeolian-palaeosol record. The 14C AMS ages are consistent and fit well within the time window of ∼45–50 ka. Considering the thicknesses (at corresponding stratigraphic heights), the ages obtained for the S1 palaeosol layer provided high resolution ages for the early Holocene period. When compared to the sedimentation rate based time estimates for the successive layers showed direct relationship between absolute ages and the time involved in the deposition. Based on the extrapolation of 14C AMS ages of the Shankerpora section, the incidences of glaciations occurred at 67–71 ka and 124–127 ka. The glacial and interglacial cycles spanning ∼130 ka encompass a variable number of palaeosols. Temporally, these observations correlate well with the two glaciations earlier reported from the loess palaeosol succession of Xiagaoyuan, Gansu Province, western Chinese Loess Plateau, suggesting perhaps that similar climatic conditions prevailed in this region.

Neogene and Pleistocene history of Agave lechuguilla in the Chihuahuan Desert

AbstractAimThe history of Agave lechuguilla, a characteristic and dominant plant of the Chihuahuan Desert, was reconstructed in order to determine the importance of the Neogene orogenic uplift and the Quaternary glacial–interglacial climatic changes on the genetic patterns of a native Chihuahuan Desert species.LocationChihuahuan Desert, Mexico and United States.MethodsChloroplast DNA data from A. lechuguilla were analysed to describe levels of genetic diversity and structure and to infer the species’ demographic history, using traditional methods and approximate Bayesian computation (ABC). The time of divergence of the different haplogroups was estimated with a Bayesian approach. In addition, ecological niche modelling was used to identify possible refugia.ResultsMolecular dating analyses showed that A. lechuguilla originated 4.46 Ma and later differentiated into four haplogroups. The average chloroplast genetic diversity was low (Hd, 0.24), with high levels of genetic differentiation (GST, 0.780). Demographic analysis, niche modelling and ABC indicated a recent expansion from at least five glacial refugia located south of the species’ current distribution.Main conclusionAgave lechuguilla originated in the Neogene, and the glacial–interglacial events of the Pleistocene resulted in the expansion and contraction of its range, playing an important role in its intraspecific diversification. These contraction–expansion events are consistent with biogeographical regions previously identified in the Chihuahuan Desert.

Phylogenetic assemblage structure of North American trees is more strongly shaped by glacial-interglacial climate variability in gymnosperms than in angiosperms.

How fast does biodiversity respond to climate change? The relationship of past and current climate with phylogenetic assemblage structure helps us to understand this question. Studies of angiosperm tree diversity in North America have already suggested effects of current water–energy balance and tropical niche conservatism. However, the role of glacial–interglacial climate variability remains to be determined, and little is known about any of these relationships for gymnosperms. Moreover, phylogenetic endemism, the concentration of unique lineages in restricted ranges, may also be related to glacial–interglacial climate variability and needs more attention. We used a refined phylogeny of both angiosperms and gymnosperms to map phylogenetic diversity, clustering and endemism of North American trees in 100‐km grid cells, and climate change velocity since Last Glacial Maximum together with postglacial accessibility to recolonization to quantify glacial–interglacial climate variability. We found: (1) Current climate is the dominant factor explaining the overall patterns, with more clustered angiosperm assemblages toward lower temperature, consistent with tropical niche conservatism. (2) Long‐term climate stability is associated with higher angiosperm endemism, while higher postglacial accessibility is linked to to more phylogenetic clustering and endemism in gymnosperms. (3) Factors linked to glacial–interglacial climate change have stronger effects on gymnosperms than on angiosperms. These results suggest that paleoclimate legacies supplement current climate in shaping phylogenetic patterns in North American trees, and especially so for gymnosperms.

Functional diversity of North American broad‐leaved trees is codetermined by past and current environmental factors

AbstractModern and historical climate are known to codetermine broad‐scale species richness and composition patterns in temperate regions. Nonetheless, is poorly understood the extent to which these effects individually or in combination determine functional diversity, many studies have simply assumed equilibrium between current climate and functional diversity. We estimated functional richness (FRich) and dispersion (FDisp) of North American broad‐leaved trees by combining distribution and trait information. Then, we determined if contemporary water‐energy availability, current topographic variability, historical climatic stability, and lagged immigration from glacial refugia co‐determined the functional diversity of North American broad‐leaved trees. We did this by assessing the directionality, magnitude, and relative importance of various contemporary and historical environmental factors know to affect species diversity. Contrasts were performed across all North America (Mexico, United States, and Canada), and areas within this region that were glaciated or ice‐free during the Last Glacial Maximum (~21 000 yr ago). FRich and FDisp showed distinct geographic patterns that are strongly associated with both contemporary environmental conditions and glacial–interglacial climate change. Model averaged regression coefficients and AIC‐based variable relative importance estimates show that contemporary productivity (FRich‐wAIC: 1.0; FDisp‐wAIC: 1.0), annual precipitation (FRich‐wAIC: 0.81; FDisp‐wAIC: 1.0), and accessibility to glacial refugia (FRich‐wAIC: 0.92; FDisp‐wAIC: 1.0) have the strongest associations to FRich and FDisp. Furthermore, the association of functional diversity with topographic heterogeneity showed steeper slopes in ice‐free regions. These findings suggest that, contrary to the expectation climate‐diversity equilibrium, functional diversity of North America broad‐leaved trees is codetermined by current climate and lagged immigration from glacial refugia.