Quaternary Climate Change Research Articles

Forcing of late Pleistocene ice volume by spatially variable summer energy

Changes in Earth’s orbit set the pace of glacial cycles, but the role of spatial variability in the insolation forcing of global ice volume remains unknown. Here, we leverage the intrinsic dynamical information in empirical records to show that ice volume responded to summer energy at high northern latitudes, as predicted by Milankovitch theory. However, the external forcing of ice volume encompasses insolation signals with a wide range of orbital frequency content, and cannot be fully accounted for by a unique time series. Southern mid-latitude insolation forcing coincides with the position of the subtropical front and the westerlies, which have been implicated in Quaternary climate changes. Dominant forcing modes at northern mid-latitudes are anti-phased with the canonical Milankovitch forcing, consistent with ice volume sensitivity to latitudinal insolation gradients.

Late Quaternary palaeoclimates and human-environment dynamics of the Maloti-Drakensberg region, southern Africa

The Maloti-Drakensberg Mountains are southern Africa's highest and lie at a crucial interface between the sub-continent's drier, colder, more seasonal interior and its perennially productive sub-tropical coastal belt. Their location, high elevation, and topography make them ideal for exploring human responses to late Quaternary climatic change. This paper reviews and synthesizes palaeoclimatic and palaeoenvironmental data from the Maloti-Drakensberg region over the past 50,000 years. It then employs 325 calibrated radiocarbon dates to examine human occupational trends across the region and its component parts, discuss human-environment dynamics over this time-span, and explore patterning between particular phases of climatic change and the timing, mode, and motives of its exploitation by people. Key findings are that the region's Lesotho core may have served as a refugium for human populations during drier, more unstable climatic periods and that intensified exploitation of freshwater fish likely helped address resource stress in cooler ones. An agenda for future palaeoenvironmental and archaeological research is also mapped out.

Formation of disjunct plant distributions in Northeast Asia: a case study of Betula davurica using a species distribution model

Repeated climate change during glacial and interglacial periods of the Quaternary led to mass migrations that resulted in disjunct distributions for many species. However, few studies have examined the processes that form disjunct distributions in Northeast Asia (NEA). In this study, we examined the disjunct distribution of Betula davurica Pall. in the Japanese archipelago. This species is a dominant canopy tree found in cool-temperate deciduous broad-leaved forests of continental NEA. We hypothesized that Quaternary climate change caused the present disjunct distribution pattern of this species. To test this hypothesis, we adopted a species distribution model and examined a series of potential habitats in the Last Glacial Maximum (LGM), the mid-Holocene, and the present. We generated models in MaxEnt with B. davurica presence as the response variable and six bioclimatic variables as predictor variables. During the LGM, projected potential habitats were distributed around the Korean Peninsula, East China, and the Japanese archipelago, excluding Hokkaido. In the mid-Holocene, habitats retreated both from East China and western Japan, remained unchanged in the Korean Peninsula and central Honshu mountains, and expanded to northern China, the Russian Far East, as well as northern Japan (Hokkaido). Thus, post-LGM global warming led to an expansion of B. davurica distribution to northern parts of continental NEA, along with a retreat in the Japanese archipelago. This shift in populations formed the present disjunct distribution.

Phylogeography of the critically endangered neotropical annual fish, Austrolebias wolterstorffi (Cyprinodontiformes: Aplocheilidae): genetic and morphometric evidence of a new species complex

Austrolebias wolterstorffi is a critically endangered annual fish, occurring in temporary ponds in a restricted area of Southern Brazil and Uruguay. Here, we evaluate the levels of genetic diversity and morphometric differentiation presented by A. wolterstorffi, attempting to reconstruct the spatiotemporal scenario by which this species reached their current distribution. Part of the mitochondrial cytochrome b and nuclear rhodopsin genes were characterized and analysed for a set of 122 and 110 specimens, respectively, collected along the entire distribution range of the species. Additionally, shape variations were evaluated for 92 individuals (43 males and 49 females) through geometric morphometric methods. Our analyses demonstrated several cases of significantly high levels of genetic differentiation among individual populations, in an isolation-by-distance pattern of divergence, with at least six different population groups along the Patos-Mirim lagoon. These groups differed by a minimum of 0.9% and a maximum of 2.6% of corrected cyt b nucleotide distances and did not share any mitochondrial haplotype. Such a pattern, added to the slight morphometric differentiation detected for most of the groups, suggests the occurrence of incipient speciation as consequence of allopatric fragmentation. The chronophylogenetic tree performed with the concatenated dataset supported independent oriental and occidental colonization routes, with the population located in the northwest part of the Rio Grande do Sul coastal plain presenting the most ancient divergence. In general, the recovered biogeographic patterns are highly consistent with the records of Quaternary climatic changes and depositional events that have occurred along the area inhabited by the studied species. This allowed us to establish a molecular clock calibration system for Neotropical annual fish. Thus, although the taxonomic status of each of the detected population units needs further study, it is clear that independent conservation strategies must be taken in each of the major areas covered by this study, most of which are located in Brazil.

Direct response of small non-glaciated headwater catchments to Late Quaternary climate change: The Valle de la Fueva, southern Pyrenees

Topographic depressions in mountain regions function as sediment traps and their morpho-sedimentary archives provide important insight into erosion and sediment dynamics in mountain ranges. In order to establish the (direct) drivers and timing of erosion phases in the southern central Pyrenees, small non-glaciated headwater catchments in the highly erodible Valle de la Fueva drainage basin were investigated as to their morphogenetic development.Geomorphic mapping revealed three morphogenetic complexes associated with the Valle de la Fueva drainage basin development: (i) high-lying talus plateaus and lateral slopes, (ii) extensive glacis and pedimentation surfaces, and (iii) deeply incised ravines with late-stage fluvial-cut terraces. The talus slopes are the oldest preserved geomorphic units of the Valle de la Fueva and potentially denote the initial drainage basin topography. Talus bedrock and boulder exposure ages cluster yet between 21 and 40 10Be-ka, indicating that the carbonate-dominated talus surfaces were rejuvenated during the last glacial cycle (MIS 4–MIS 2). The younger morphogenetic complexes (ii, iii) point to successive basin erosion stages from diffusive surface pedimentation under cold climate conditions (ii) to rapid linear fluvial dissection and late-stage terrace formation (iii). Denoting the abandonment of pediments as actively eroding surfaces, 10Be depth profiles of glacis cover sediments yielded consistent late MIS 2 exposure ages. The abandoning of pediments marks the onset of rapid fluvial downcutting of deep ravines (iii) around the Holocene climate transition, which involved substantial sediment routing and basin scale erosion. Lower fluvial-cut terraces denote the termination of intense catchment erosion at around 14–8–10Be-ka and minor fluvial incision during Middle-Late Holocene.This research shows that small non-glaciated mountain catchments feature valuable high-resolution morpho-sedimentary archives that are useful for assessing the direct impact of major climate transitions on surface processes and landscape transformation in mountain regions. Improvements in quantifying the timing and rates of (paleo-) surface processes are vital for enhancing regional glaciofluvial chronologies and large-scale basin erosion models that are possibly afflicted with time-averaging biases.

Geología y paleolimnología del complejo lagunar ?Santa Rosa del Monte?, Provincia de Buenos Aires, Argentina

Tres lagunas integran el complejo, alojadas en cinco cubetas eólicas de diferente edad, que a nivel hídrico normal forman un ambiente único, donde se caracterizaron los aspectos fisiográficos, hidrológicos y geolimnológicos. En los afloramientos se reconocieron cinco unidades litoestratigráficas y tres pedoestratigráficas, que abarcan del Pleistoceno temprano/medio al tardío y del Pleistoceno final al presente. La Formación Ensenada, constituye el sustrato regional, sobre el cual se disponen cuatro unidades eólicas, las Formaciones Buenos Aires, La Postrera II, III, IV, los Geosuelos Sin Nombre, Puesto Callejón Viejo y Puesto Berrondo y, el aluvio reciente. En los lechos se registraron ocho unidades litoestratigráficas: cinco límnicas y tres eólicas. Las límnicas corresponden a los cuatro paleoambientes de la Formación Luján: Miembros La Chumbiada, Lobos, Río Salado y Monte, del Pleistoceno tardío al Holoceno tardío-tardío y el aluvio reciente; las unidades eólicas a las Formaciones La Postrera I y II del Pleistoceno tardío al Holoceno temprano y la IV del Holoceno tardío-tardío. El origen de las primeras cubetas se inició en la etapa seca del ?Bonaerense?, la posterior alternancia climática seco/húmedo generó las otras cubetas. Las etapas secas se caracterizaron por deflación, sabkhas, precipitación de sales y depósitos eólicos. En las húmedas predominó el aluvionamiento y la pedogénesis. Así, el conjunto de depósitos ?posensenadenses? está representado por cinco episodios secos (Glacial Temprano a la Pequeña Edad de Hielo) y cinco húmedos, con acumulaciones límnicas, desde el Miembro La Chumbiada al aluvio reciente y en los afloramientos los suelos sincrónicos S4, S2, S1 y S0.

Invoking adaptation to decipher the genetic legacy of past climate change.

Persistence of natural populations during periods of climate change is likely to depend on migration (range shifts) or adaptation. These responses were traditionally considered discrete processes and conceptually divided into the realms of ecology and evolution. In a milestone paper, Davis and Shaw (2001) Science 292:673 argued that the interplay of adaptation and migration was central to biotic responses to Quaternary climate, but since then there has been no synthesis of efforts made to set up this research program. Here we review some of the salient findings from molecular genetic studies assessing ecological and evolutionary responses to Quaternary climate change. These studies have revolutionized our understanding of population processes associated with past species migration. However, knowledge remains limited about the role of natural selection for local adaptation of populations to Quaternary environmental fluctuations and associated range shifts, and for the footprints this might have left on extant populations. Next-generation sequencing technologies, high-resolution paleoclimate analyses, and advances in population genetic theory offer an unprecedented opportunity to test hypotheses about adaptation through time. Recent population genomics studies have greatly improved our understanding of the role of contemporary adaptation to local environments in shaping spatial patterns of genetic diversity across modern-day landscapes. Advances in this burgeoning field provide important conceptual and methodological bases to decipher the historical role of natural selection and assess adaptation to past environmental variation. We suggest that a process called "temporal conditional neutrality" has taken place: some alleles favored in glacial environments become selectively neutral in modern-day conditions, whereas some alleles that had been neutral during glacial periods become under selection in modern environments. Building on this view, we present a new integrative framework for addressing the interplay of demographic and adaptive evolutionary responses to Quaternary climate dynamics, the research agenda initially envisioned by Davis and Shaw (2001) Science 292:673.

Luminescence dating and palaeomagnetic age constraint of a last glacial loess-palaeosol sequence from Istria, Croatia

Loess and loess-like deposits with intercalated palaeosols are widely distributed in Croatia, particularly in the Pannonian basin in the east and along the Adriatic Coast in the west, which have provided invaluable evidences of Quaternary climate change. The timing, provenance and spatial distribution of such loess deposits have long been a major research interest. In the current study, a ∼8-m-thick loess-palaeosol sequence located near the town of Savudrija (Savudrija Section), on the northern-most cape of the Istrian Peninsula on the Adriatic Coast, is investigated. Multiple approaches of luminescence dating and palaeomagnetic age constraint are conducted to understand the timing of the regional aeolian activities and its implications for climate change. Seven samples were collected from the loess layers of the Savudrija section for comprehensive quartz optically stimulated luminescence (OSL) and feldspar post-IR infrared stimulation luminescence (IRSL) dating. The palaeomagnetic investigation was conducted on 82 oriented samples collected from the upper 6.7 m of the section. The quartz OSL ages of the upper four samples and the fading corrected pIRIR225 ages of the lower three samples were used to reconstruct the age framework of the section. The results demonstrate that the Savudrija loess-palaeosol sequence were formed between ∼70 ka and ∼9 ka, correlated to the time span from the last glacial to early Holocene. The variation of the magnetic susceptibility of the Savudrija section is strictly following the pattern that the palaeosol horizons generate high susceptibility values while the loess horizons show low susceptibility values. The palaeomagnetic age constraint is obtained by correlating the magnetic susceptibility record of the Savudrija section with other records, which gives the age range between 65 ka and 20 ka for the loess-palaeosol sequence (excluding the lowermost red soil). It broadly agrees with the luminescence chronology but conflicts in details, demonstrating that the correlation between the different magnetic susceptibility records is questionable. Furthermore, the magnetic susceptibility record suggests that the age of ∼70 ka of the red soil at the bottom of the section might be still ambiguous and needs further study.

High-Altitude Rock Shelters and Settlements in an African Alpine Ecosystem: The Bale Mountains National Park, Ethiopia

This first survey of rock shelters and settlements in the Bale Mountains in Ethiopia is a baseline assessment for further research into the settlement history of Africa’s largest alpine highlands. Extensive GPS-based mapping and interviews resulted in two detailed maps, a catalogue of profiles, and complete photographic documentation. In total, 331 rock shelters (four permanently inhabited, 51 seasonally inhabited, and 276 currently uninhabited) and 870 settlements (207 permanently inhabited, 449 seasonally inhabited, 214 uninhabited) were recorded together with information about the activities and livelihoods of the inhabitants of the current settlements. This 2015 study was part of the Ethiopian-European research project “The mountain exile hypothesis – how humans benefited from and re-shaped African high-altitude ecosystems during Quaternary climate changes” (DFG FOR 2358). It was designed to support future management plans in this internationally important conservation area that has recently faced increasing land-use pressure and the threat of degradation.

Unveiling the History of a Peculiar Weevil-Plant Interaction in South America: A Phylogeographic Approach to Hydnorobius hydnorae (Belidae) Associated with Prosopanche americana (Aristolochiaceae)

Interspecific interactions take place over both long and short time-frames. However, it is not completely understood if the interacting-partners persisted, migrated, or expanded in concert with Quaternary climate and landscape changes. We aim to understand whether there is concordance between the specialist weevil Hydnorobius hydnorae and its parasitic host plant, Prosopanche americana in space and time. We aim to determine whether Prosopanche had already established its range, and Hydnorobius later actively colonized this rare resource; or, if both host plant and herbivore expanded their range concomitantly. We performed population genetic, phylogeographic and Bayesian diffusion analysis of Cytochrome B sequences from 18 weevil localities and used paleodistribution models to infer host plant dispersal patterns. We found strong but uneven population structure across the range for H. hydnorae with weak signals of population growth, and haplotype network structure and SAMOVA groupings closely following biogeographic region boundaries. The ancestral areas for both Hydnorobius and Prosopanche are reconstructed in San Luis province within the Chaco Biogeographic province. Our results indicate a long trajectory of host-tracking through space and time, where the weevil has expanded its geographic range following its host plant, without significant demographic growth. We explore the past environmental changes that could underlie the boundaries between locality groups. We suggest that geographic dispersal without population growth in Hydnorobius could be enabled by the scarcity of the host plant itself, allowing for slow expansion rates and stable populations, with no need for significant demographic growth pulses to support range expansion.

Evolution of the insectivore assemblages (Eulipotyphla, Mammalia) in Spain and their relation with Neogene and Quaternary climatic changes

Furio, M., van den Hoek Ostende, L.W., Agusti, J., Minwer-Barakat, R. 2018. Evolution of the insectivore assemblages (Eulipotyphla, Mammalia) in Spain and their relation with Neogene and Quaternary climatic changes. Ecosistemas 27(1): 38-51. Doi.: 10.7818/ECOS.1454 The knowledge of the Neogene and Quaternary fossil record of the insectivores, the small mammals included in the order Eulipotyphla, has been greatly improved in the last two decades. This improvement, linked to a refinement on the dating of many Spanish fossil localities, allows tracking the evolution of the insectivore assemblages during the last 20 million years leading to the Recent communities. Given the sensitivity of these species to certain environmental conditions within the Iberian geographic context, the changes on the insectivore diversity at generic level can be confidently associated to some biological events and linked to the large-scale climatic trends in the Northern Hemisphere.

How will climate novelty influence ecological forecasts? Using the Quaternary to assess future reliability.

Future climates are projected to be highly novel relative to recent climates. Climate novelty challenges models that correlate ecological patterns to climate variables and then use these relationships to forecast ecological responses to future climate change. Here, we quantify the magnitude and ecological significance of future climate novelty by comparing it to novel climates over the past 21,000years in North America. We then use relationships between model performance and climate novelty derived from the fossil pollen record from eastern North America to estimate the expected decrease in predictive skill of ecological forecasting models as future climate novelty increases. We show that, in the high emissions scenario (RCP 8.5) and by late 21st century, future climate novelty is similar to or higher than peak levels of climate novelty over the last 21,000years. The accuracy of ecological forecasting models is projected to decline steadily over the coming decades in response to increasing climate novelty, although models that incorporate co-occurrences among species may retain somewhat higher predictive skill. In addition to quantifying future climate novelty in the context of late Quaternary climate change, this work underscores the challenges of making reliable forecasts to an increasingly novel future, while highlighting the need to assess potential avenues for improvement, such as increased reliance on geological analogs for future novel climates and improving existing models by pooling data through time and incorporating assemblage-level information.

Biogeographical structure and endemism pattern in reptiles of the Western Palearctic

The analysis of biogeographical structure and patterns of endemism are central topics of biogeography, but require exhaustive distribution data. A lack of accurate broad-scale information on the distribution of reptiles has so far limited the analyses of biogeographical structure. Here we analysed the distribution of reptiles within the broad-sense Western Palearctic to assess biogeographical regionalization using phylogenetic and non-phylogenetic approaches, identified areas of endemism and evaluated the environmental factors promoting community uniqueness and endemism. We gathered distributional records from the literature and from the field, mapping the distribution of all the Western Palearctic reptiles on a 1-degree resolution grid. βsimdissimilarity and hierarchical clustering was used to identify bioregions, analysing data both at the species and at the genus level, and considering phylogenetic dissimilarity. Consensus areas of endemism were identified on the basis of the optimality criterion. We then assessed whether biogeographical structure is related to present-day climate, insularity, orography and velocity of climate change during the Late Quaternary. The genus-level analysis identified five main biogeographical regions within the Western Palearctic, in partial agreement with previous proposals, while the species-level analysis identified more bioregions, largely by dividing the ones identified by genera. Phylogenetic bioregions were generally consistent with the non-phylogenetic ones. The strongest community uniqueness was observed in subtropical warm climates with seasonal precipitation and low productivity. We found nine consensus areas of endemism, mostly in regions with limited velocity of Quaternary climate change and warm subtropical climates. The biogeographical structure of Western Palearctic reptiles is comparable to what has been observed in other vertebrates, with a clear distinction between the Saharo-Arabian-Sindian and Euro-Mediterranean herpetofaunas. Unlike other vertebrates, in reptiles the highest uniqueness and endemism is observed in dry climates, but the velocity of climate change during the Quaternary remains a major driver of endemism across all the vertebrates.

Evolutionary persistence in Gunnera and the contribution of southern plant groups to the tropical Andes biodiversity hotspot.

Several studies have demonstrated the contribution of northern immigrants to the flora of the tropical Andes—the world’s richest and most diverse biodiversity hotspot. However, much less is known about the biogeographic history and diversification of Andean groups with southern origins, although it has been suggested that northern and southern groups have contributed roughly equally to the high Andean (i.e., páramo) flora. Here we infer the evolutionary history of the southern hemisphere plant genus Gunnera, a lineage with a rich fossil history and an important ecological role as an early colonising species characteristic of wet, montane environments. Our results show striking contrasts in species diversification, where some species may have persisted for some 90 million years, and whereas others date to less than 2 Ma since origination. The outstanding longevity of the group is likely linked to a high degree of niche conservatism across its highly disjunct range, whereby Gunnera tracks damp and boggy soils in cool habitats. Colonisation of the northern Andes is related to Quaternary climate change, with subsequent rapid diversification appearing to be driven by their ability to take advantage of environmental opportunities. This study demonstrates the composite origin of a mega-diverse biota.

Neither barriers nor refugia explain genetic structure in a major biogeographic break: phylogeography of praying mantises in the Brazilian Atlantic Forest

The Atlantic Forest is one of the world’s top biodiversity hotspots, but the diversification processes of its biota are still poorly known, with competing models attributing dominant roles to either Quaternary climatic changes or geographic barriers. Many studies identify the Doce river as a major phylogeographic break, but the reasons for this phenomenon are highly debated. Here we test the predictions of the refugial and barrier models for a common species of praying mantis, Miobantia fuscata, focusing in the areas immediately south and north of the Doce river. Our analyses show high intraspecific genetic diversity, deep coalescence times and no evidence for recent population expansion. Phylogeographic structure is inconsistent with a refugial hypothesis. Significant gene flow between northern and southern populations also conflicts with a strong role for geographic barriers. This study highlights the need for considering invertebrate taxa to infer recent landscape changes, and points towards a more complex picture of genetic diversification in the Atlantic Forest.

Eolian dust dispersal patterns since the last glacial period in eastern Central Asia: insights from a loess-paleosol sequence in the Ili Basin

Abstract. The extensive loess deposits of the Eurasian mid-latitudes provide important terrestrial archives of Quaternary climatic change. As yet, however, loess records in Central Asia are poorly understood. Here we investigate the grain size and magnetic characteristics of loess from the Nilka (NLK) section in the Ili Basin of eastern Central Asia. Weak pedogenesis suggested by frequency-dependent magnetic susceptibility (χfd%) and magnetic susceptibility (MS) peaks in primary loess suggest that MS is more strongly influenced by allogenetic magnetic minerals than pedogenesis, and may therefore be used to indicate wind strength. This is supported by the close correlation between variations in MS and proportions of the sand-sized fraction. To further explore the temporal variability in dust transport patterns, we identified three grain size end-members (EM1, mode size 47.5 µm; EM2, 33.6 µm; EM3, 18.9 µm) which represent distinct aerodynamic environments. EM1 and EM2 are inferred to represent grain size fractions transported from proximal sources in short-term, near-surface suspension during dust outbreaks. EM3 appears to represent a continuous background dust fraction under non-dust storm conditions. Of the three end-members, EM1 is most likely the most sensitive recorder of wind strength. We compare our EM1 proportions with mean grain size from the Jingyuan section in the Chinese loess plateau, and assess these in the context of modern and Holocene climate data. Our research suggests that the Siberian High pressure system is the dominant influence on wind dynamics, resulting in loess deposition in the eastern Ili Basin. Six millennial-scale cooling (Heinrich) events can be identified in the NLK loess records. Our grain size data support the hypothesis that the Siberian High acts as teleconnection between the climatic systems of the North Atlantic and East Asia in the high northern latitudes, but not for the mid-latitude westerlies.

Fe-oxide mineralogy of the Jiujiang red earth sediments and implications for Quaternary climate change, southern China

Diffuse reflectance spectrophotometry (DRS) is a new, fast, and reliable method to characterize Fe-oxides in soils. The Fe-oxide mineralogy of the Jiujiang red earth sediments was investigated using DRS to investigate the climate evolution of southern China since the mid-Pleistocene. The DRS results show that hematite/(hematite + goethite) ratios [Hm/(Hm + Gt)] exhibit an upward decreasing trend within the Jiujiang section, suggesting a gradual climate change from warm and humid in the middle Pleistocene to cooler and drier in the late Pleistocene. Upsection trends toward higher (orthoclase + plagioclase)/quartz ratios [(Or + Pl)/Q] and magnetic susceptibility values (χlf) support this inference, which accords with global climate trends at that time. However, higher-frequency climatic subcycles observed in loess sections of northern China are not evident in the Jiujiang records, indicating a relatively lower climate sensitivity of the red earth sediments in southern China.

Synchronic historical patterns of species diversification in seasonal aplocheiloid killifishes of the semi-arid Brazilian Caatinga.

The Caatinga is the largest nucleus of seasonally dry tropical forests in South America, but little is known about the evolutionary history and biogeography of endemic organisms. Evolutionary diversification and distribution of terrestrial vertebrates endemic to the Caatinga have been explained by palaeogeographical Neogene episodes, mostly related to changes in the course of the São Francisco River, the largest river in the region. Our objective is to estimate the timing of divergence of two endemic groups of short-lived seasonal killifishes inhabiting all ecoregions of the Caatinga, testing the occurrence of synchronic events of spatial diversification in light of available data on regional palaeogeography. We performed independent time-calibrated phylogenetic molecular analyses for two clades of sympatric and geographically widespread seasonal killifishes endemic to the Caatinga, the Hypsolebias antenori group and the Cynolebias alpha-clade. Our results consistently indicate that species diversification took place synchronically in both groups, as well as it is contemporary to diversification of other organisms adapted to life in the semi-arid Caatinga, including lizards and small mammals. Both groups originated during the Miocene, but species diversification started between the Late Miocene and Early Pliocene, when global cooling probably favoured the expansion of semi-arid areas. Synchronic diversification patterns found are chronologically related to Tertiary palaeogeographical reorganizations associated to continental drift and to Quaternary climatic changes, corroborating the recent proposal that South American biodiversity has been continuously shaped between the Late Paleogene and Pleistocene.

Radiometric dating of late Quaternary loess in the northern piedmont of South Tianshan Mountains: Implications for reliable dating

Reliable chronologies are prerequisites when interpreting proxy records in terrestrial archives of Quaternary climate and environmental change. Optically stimulated luminescence (OSL) dating and accelerator mass spectrometry radiocarbon dating (AMS 14C) are commonly used to date late Quaternary loess deposits in the Chinese Loess Plateau, but the range and reliability of the two methods in Central Asia are still debated. In this study, we investigate both fine‐grained quartz OSL and AMS 14C dating of a late Quaternary loess section located at the northern piedmont of the South Tianshan Mountains in Central Asia and discuss the reliability of the two radiometric dating methods. The results show that the OSL and AMS 14C ages are generally consistent with the stratigraphic sequence when the ages are younger than 25 cal ka BP, which means that both can be used to establish a reliable chronology in the Ili Basin. But beyond this age, the OSL dating method seems to be a more reliable approach. The results also supported previous dates based on medium‐grained quartz OSL dating of the Ili loess in the southern piedmont of the North Tianshan Mountains. Radiocarbon ages older than 25 cal ka BP should be treated with caution, and attention must be paid to the influence of pedoturbation on OSL signals in the Central Asian loess. Multiple dating approaches for mutual authentication and exploring new dating materials are suggested in further loess chronological research. These findings will be helpful in establishing a reliable timescale and in reconstructing high‐resolution environmental change in Central Asia.

Mitochondrial phylogeography of the Iberian endemic frog Rana iberica, with implications for its conservation.

Genetic characterization of species using phylogeographic approaches represents a basic reference to understand their evolutionary history as well as to identify conservation priorities to protect areas of particular interest regarding evolutionary potential. Even in well-studied regions such information is lacking for the majority of species, including many endemic species with reduced distribution ranges. We investigate the phylogeographic pattern of the Iberian frog Rana iberica, an endemic amphibian restricted to Central and North-Western Iberian Peninsula. Using mitochondrial sequences, we reconstruct the phylogeographic history of the species to test the effect of Quaternary climate changes on the evolutionary diversification of lineages, that is, the differentiation of mitochondrial lineages and the formation of genetic diversity melting pots, and integrate phylogeographic evidence for future conservation planning. Our results indicate the existence of 3 main mitochondrial lineages differentiated during the Upper Pleistocene. Both historical demographic analyses and climatic niche modeling show a strong effect of glacial climate changes, suggesting recurrent range contractions and expansions. Under such circumstances, differentiation took place most likely by isolation in allopatric interglacial refugia. Secondary lineage admixture in northern Portugal generated a broad mixed zone with highest nucleotide diversity. Given its particular evolutionary potential, its reduced distribution and eventual threats under current climate change scenario, conservation priorities should focus on the isolated lineage from Sierra de Guadalupe.