Early-Middle Pleistocene Transition Research Articles

Impacts of Quaternary climatic changes on the diversification of riverine cichlids in the lower Congo River.

Climatic and geomorphological changes during the Quaternary period impacted global patterns of speciation and diversification across a wide range of taxa, but few studies have examined these effects on African riverine fishes. The lower Congo River is an excellent natural laboratory for understanding complex speciation and population diversification processes as it is hydrologically extremely dynamic and recognized as a continental hotspot of diversity harboring many narrowly endemic species. A previous study using genome-wide SNP data highlighted the importance of dynamic hydrological regimes to the diversification and speciation in lower Congo River cichlids. However, historical climate and hydrological changes (e.g., reduced river discharge during extended dry periods) have likely also influenced ichthyofaunal diversification processes in this system. The lower Congo River offers a unique opportunity to study climate-driven changes in river discharge, given the massive volume of water from the entire Congo basin flowing through this short stretch of the river. Here, we, for the first time, investigate the impacts of paleoclimatic factors on ichthyofaunal diversification in this system by inferring divergence times and modeling patterns of gene flow in four endemic lamprologine cichlids, including the blind cichlid, Lamprologus lethops. Our results suggest that Quaternary climate changes associated with river discharge fluctuations may have impacted the diversification of species along the system. Our study, using reduced representation sequencing (2RADseq), indicates that the lower Congo River lamprologines emerged during the Early-Middle Pleistocene transition, characterized as one of the earth's major climatic transformation periods. Modeling results suggest that gene flow across populations and between species was not constant but occurred in temporally constrained pulses. We show that these results correlate with glacial-interglacial fluctuations. The current hyper-diverse fish assemblages of the lower Congo River riverscape likely reflect the synergistic effects of multiple drivers fueling complex evolutionary processes through time.

Controls on long-term changes in bathyal bivalve biomass: The Pleistocene glacial–interglacial record in the eastern Mediterranean

The biomass of aquatic organisms largely determines the mass and energy flow within an ecosystem, but the long-term impact of environmental change on biomass is not well constrained for a number of clades. Here, we test the hypothesis that bivalve biomass is negatively impacted by warming climate over time. This study is based on a fossil marine bivalve fauna recovered from hemipelagic sediments deposited in the eastern Mediterranean during climate cycles (marine isotope stages (MIS) 22–18; 900–712 kyr B.P.) of the Early–Middle Pleistocene Transition. We reconstruct individual shell biomasses from fossils and discuss the various biotic and abiotic factors that controlled long-term shell biomass patterns across this important interval in the Earth climate system. The results are contrary to the original hypothesis, suggesting that the response to temperature is not universal. Nevertheless, a decrease in median biomass is observed during the MIS 19 warm period and can be possibly attributed to the combined effect of multiple drivers that cooperated at that critical time in the past, including higher temperature and primary productivity, reduced ventilation of the sea floor, biodiversity changes due to geographic range shifts, and considering species- and age-specific thermal tolerances. Generally, bivalve biomass at the community level is determined by relative abundance and shell biomass-frequency distribution. In our study, the relative abundance and median biomass of small species do not increase or decrease, respectively, in warmer periods. However, larger species are negatively affected by warming both in terms of relative abundance and biomass.

Evolutionary history of Castanea sativa in the Caucasus driven by Middle and Late Pleistocene paleoenvironmental changes.

Due to global climate cooling and aridification since the Paleogene, members of the Neogene flora were extirpated from the Northern Hemisphere or were confined to a few refugial areas. For some species, the final reduction/extinction came in the Pleistocene, but some others have survived climatic transformations up to the present. This has occurred in Castanea sativa, a species of high commercial value in Europe and a significant component of the Caucasian forests' biodiversity. In contrast to the European range, neither the historical biogeography nor the population genetic structure of the species in its isolated Caucasian range has been clarified. Here, based on a survey of 21 natural populations from the Caucasus and a single one from Europe, we provide a likely biogeographic reconstruction and genetic diversity details. By applying Bayesian inference, species distribution modelling and fossil pollen data, we estimated (i) the time of the Caucasian-European divergence during the Middle Pleistocene, (ii) the time of divergence among Caucasian lineages and (iii) outlined the glacial refugia for species. The climate changes related to the Early-Middle Pleistocene Transition are proposed as the major drivers of the intraspecific divergence and European-Caucasian disjunction for the species, while the impact of the last glacial cycle was of marginal importance.

Hydroclimate reconstructions in the Suguta Valley, northern Kenya, during the Early-Middle Pleistocene Transition

The Early-Middle Pleistocene Transition (EMPT) between 1200 and 700 ka represents a major global climate transition from dominantly 41,000- to 100,000-year glacial cycles. The forces and mechanisms behind this transition and the response of African environments are not well understood. The active volcanism and tectonics of the East African Rift System add complexity to local environmental systems and can erase important proxy records, inhibiting studies of lacustrine dynamics. As a result, there is minimal understanding of how this transition impacted the region's lake systems. At Paleolake Suguta, in the northern Kenya Rift, however, flood basalts cap lacustrine EMPT-age deposits, preserving these strata and their valuable paleoenvironmental record. This research presents a high-resolution reconstruction of hydrological change from approximately 931 to 831 ka within the Suguta-Turkana Basin in the northern Kenya Rift. Paleolake dynamics are reconstructed from a 41 m sedimentary section using diatom morphology, sedimentology, and X-Ray Fluorescence elemental analysis. Results show that lake levels varied greatly during this part of the EMPT with two wetter phases and two drier phases developing over about 100 kyr. From ∼885–831 ka, especially, the Suguta-Turkana Basin exhibits rapid changes in paleohydrology, ranging between deep stratified lakes; shallow, well-mixed lakes; and complete desiccation, with some of these changes occurring on an order of hundreds of years. This EMPT Suguta-Turkana-Baringo record therefore provides valuable insight into hydroclimate variability at an overall resolution of several thousand years, allowing reconstruction of past environments during a period of poorly understood terrestrial environmental change.

Patterns and cyclicity of Quaternary sedimentation above a subducting seamount at Rock Garden (Central Hikurangi margin, New Zealand)

Rock Garden (RG), located east off the North Island of New Zealand, is part of an accretionary ridge that is influenced by seamount subduction. Two ∼37 m long sediment cores, drilled with the seafloor drill rig (MeBo200) from RG, provide a continuous sedimentary record of the period between 1.95 and 0.4 Ma. This period, the Early-Middle Pleistocene transition (EMPT), was marked by a progressive increase in the amplitude of climate oscillations, and a shift of Milanković cycles from 41 ka towards a quasi-100 ka frequency in the absence of any significant change in orbital forcing. From the recovered core material of cores GeoB 20824–4 and GeoB 20846–1, we determined sediment physical properties, oxygen isotope (δ18O) values, and element concentration based on X-ray fluorescence (XRF) measurements. The element ratios were used as proxies for sediment composition and as paleo-environmental indices. In sediment physical properties, δ18O values, and geochemical properties, evidence for glacial and interglacial cycles and spectral periods of 405, 100, 41 ka were found. A shift of the spectral period from 41 to 100 ka took place in sediment cores during (1.4 to 0.4 Ma). Numerical ages obtained from tephra layers included in the sedimentary record enabled to estimate sedimentation rates from both cores. Although both drill sites are only 1800 m away from each other, sedimentation rates of 2.15 to 2.96 cm ka−1 (GeoB 20824–4) and 5.49 to 6.77 cm ka−1 (GeoB 20846–1), respectively, differ by a factor of two. This may be the reason why two facies-units were identified in core GeoB 20824–4, whereas sediments of core GeoB 20846–1 all belong to the same facies. A change of lithofacies in core GeoB 20824–4 between Unit I and Unit II in ∼20 mbsf at 1.5 to 1.4 Ma marks the initiation of the EMPT.

A review on the Pleistocene occurrences and palaeobiology of Hippopotamus antiquus based on the record from the Barranc de la Boella Section (Francolí Basin, NE Iberia)

The study of European Pleistocene Hippopotamus presents unresolved questions and a lack of consensus among specialists being matter of hotly debate in the last decades. The number of taxa, their geographical and chronological distribution and their palaeobiological affinities are still under evaluation. The present work presents the results of comparative analyses using descriptive anatomy, linear biometry and geometric morphometrics of Hippopotamus specimens found in the archaeopalaeontological outcrops of the Barranc de la Boella Section (Francolí Basin, NE Iberian Peninsula) and other coeval European sites in the context of the record of the genus Hippopotamus in Europe and its putative migrations from Africa. The deposits from Barranc de la Boella Section documented for the first time the presence of hominids with Acheulian technology and hippos roughly coinciding with the Early-Middle Pleistocene Transition (EMPT), one of the periods with strongest climate asymmetry throughout the Pleistocene. The evaluation of the studied specimens and the other European record favor the consideration of Hippopotamus antiquus as the only taxon of its family present in Europe from the Early Pleistocene (ca. 2.1 Ma) to the mid-Middle Pleistocene (ca. 0.4 Ma), when the extant species (Hippopotamus amphibius) dispersed from Africa. Even so, there is a need for a more detailed understanding of the large intraspecific variability and sexual dimorphism reported within the genus Hippopotamus to characterise the phenotype of individuals in its populations across different chronologies, geographic locations, and environmental conditions. The detailed review of the distribution of H. antiquus during the EMPT raises the possibility that the Iberian and Italic peninsulas acted as climatic refugia for its populations strongly dependents of the aquatic environment during the coldest climatic stages (e.g. MIS 22).

Phylogeographic analysis revealed allopatric distribution pattern and biogeographic processes of the widespread pale chub Opsariichthys acutipinnis-evolans complex (Teleostei: Cyprinidae) in southeastern China

Understanding phylogeographic patterns of widespread species can provide insights into their speciation processes and guide the conservation and management measures. In the present study, Cyt b sequences were used to investigate the phylogeographic structure of the Opsariichthys acutipinnis-evolans complex in southeastern China. The gene tree revealed six major lineages (lineage A-F) which were distributed allopatrically, with lineage B distributed in the western part (middle Yangtze and Pearl River) and the other lineages in the eastern part (lower Yangtze and coastal waters of southeastern China). Dating of the lineage diversification revealed the early eastward-westward divergence separating lineage A, B, and C during the late Pliocene and early Pleistocene (3.00, 2.61, and 2.12 Ma, respectively), possibly due to the uplift of the Qinghai-Tibetan Plateau and subsequent orogenies in southeastern China. The following northward-southward diversification resulted in the separation of lineage D, E, and F in the early-middle Pleistocene (1.33 and 0.95 Ma), likely associated with the enhanced succession of glacial cycles during the Early-Middle Pleistocene transition. Although the genetic divergence of 0.017–0.070 among lineages indicated possible different species, morphological characters failed to separate them. Therefore, they were treated as a species complex. Given the distinct genetic divergence of the various lineages, they were suggested as different evolutionary significant units.

THE QUIBAS SITE (MURCIA, SPAIN): NEW HERBIVORES FROM THE EARLY-MIDDLE PLEISTOCENE TRANSITION

The Lower Pleistocene site of Quibas, in Sierra de Quibas (Murcia, Spain) was discovered in 1994 and has since then provided abundant material of typical Epivillafranchian taxa. This biochron belongs to the Early-Middle Pleistocene transition (1.2 – 0.78 Ma), characterised by a change in orbital cyclicity from a 41 kyr cycle to 100 kyr that intensified the climate and culminated in the most important faunal turnover of the Pleistocene regarding large mammals. The Group of Palaeoanthropology of the National Museum of Natural Sciences (CSIC, Spain) and the Institut Català de Paleoecologia Humana i Evolució Social (IPHES-CERCA, Spain) carried out four field seasons from 2015 to 2018. Here we present the large herbivorous mammals recovered from the field, including the first citation of two taxa new to the locality: Stephanorhinus cf. etruscus and Bison cf. voigtstedtensis. We also provide the first description of previously mentioned taxa: Dama cf. vallonnetensis and Sus sp. Together with the remaining herbivores, the faunal community shows a strong European affinity with some regionalism. Compared with other Iberian localities, the site of Quibas stands out for the lack of hominin fossils or any evidence supporting their presence in the area, a peculiar scenario given that the Early-Middle Pleistocene transition broadly speaking sees the arrival of humans into Europe.

Searching for potential multi-hazard events during the last 1.5 million years of the Pleistocene epoch

Increasing attention has been paid to multi-hazards in environmental disaster studies produced during the last decade. Multi-hazard studies focus on the occurrence, interaction and effect of several natural hazards in the same region. Despite the increasing number of multi-hazard studies, few investigations have focused on global-scale multi-hazard events. With the aim of closing this gap, our study focuses on the identification of periods during the last 1.5 million years of the Pleistocene epoch, with the quasi-parallel appearance of natural hazards (e.g., asteroid impacts and large volcanic eruptions with a Volcanic Explosivity Index (VEI) of 8 and 7) amplifying their individual effects and thus causing long-term, global-scale changes. Of the seven identified potential multi-hazard events, three were considered as possible global-scale events with a longer term environmental (paleoclimatic) impact; dated to c.a., 1.4 Ma (marine isotope stage – MIS45), 1.0 Ma (MIS 27), and 100 ka (MIS 5c), respectively. Two additional periods (around 50 and 20 ka) were identified as being associated with more restricted scale multi-hazard events, which might cause a “Little Ice Age-like” climatic episode in the history of the Pleistocene Period. In addition, we present a hypothesis about the complex climatic response to a global-scale multi-hazard event consisting of a series of asteroid impacts and volcanic eruption linked to a geomagnetic polarity change, namely the Matuyama-Brunhes Boundary, which might be accompanied by global cooling and result in the final step of the Early Middle Pleistocene Transition.

Paleoproductivity proxies and alkenone precursors in the Western Mediterranean during the Early-Middle Pleistocene transition

Multidisciplinary analyses (taxonomic analysis of coccolithophore assemblages, stable oxygen isotopes, marine and terrestrial biomarkers) have been carried out on sediments from Ocean Drilling Program Site 975 in the Algero-Balearic basin, through late marine isotope stage (MIS) 20-19 (800–756 ka). The aim is to compare coccolithophore paleoproductivity proxies, such as C37 alkenone concentration and nannofossil accumulation rate (NAR), and understand their relationship with paleoceanographic condition and paleoenvironmental changes, alkenone-producing precursors and unsaturated C37 alkenone compounds. The patterns of C37 alkenones and NAR provide reliable information on past paleoproductivity changes since coccolith dissolution and organic matter preservation were excluded as relevant processes at the site. This is testified by the high values of Nannofossil Dissolution Index and relation between C37 alkenone concentration and Alcohol Preservation Index, the latter used as a proxy of sea bottom ventilation in the basin. A weak mismatching between NAR and C37 alkenone concentration records has been observed and related to paleoenvironmental factors and ecological preferences of alkenone-producing species. Temperature variations mostly controlled the alternating interspecific abundance variations of these taxa through glacial-interglacial and stadial-interstadial climate phases. The percentage abundances of alkenone-producing species, Gephyrocapsa caribbeanica and Gephyrocapsa with open central area (mainly G. margerelii-G. muellerae) strongly co-varied with the percentages of C37:2 and C37:3, respectively during warm and cool-cold periods, suggesting their prominent role in producing these unsaturated C37 alkenone compounds. Moreover, Gephyrocapsa spp. with open central area > 3 μm were likely the main C37:4 producers during the colder late MIS 20 stadial and stadial phases. Other factors in addition to temperature influenced the paleoproductivity proxy patterns. The oceanographic condition established during MIS 20-MIS 19 deglaciation and the more nutrient-rich surface waters during the orbitally-controlled organic-rich layer deposition in the early MIS 19 enhanced primary productivity leading to higher production and preservation of total C37 alkenones.

Rapid genetic divergence and mitonuclear discordance in the Taliang knobby newt ( Liangshantriton taliangensis, Salamandridae, Caudata) and their driving forces.

The Hengduan Mountains Region (HMR) is the largest “evolutionary frontier” of the northern temperate zone, and the origin and maintenance of species in this area is a research hotspot. Exploring species-specific responses to historical and contemporary environmental changes will improve our understanding of the role of this region in maintaining biodiversity. In this study, mitochondrial and microsatellite diversities were used to assess the contributions of paleogeological events, Pleistocene climatic oscillations, and contemporary landscape characteristics to the rapid intraspecific diversification of Liangshantriton taliangensis, a vulnerable amphibian species endemic to several sky-island mountains in the southeastern HMR. Divergence date estimations suggested that the East Asian monsoon, local uplifting events (Xigeda Formation strata), and Early-Middle Pleistocene transition (EMPT) promoted rapid divergence of L. taliangensis during the Pleistocene, yielding eight mitochondrial lineages and six nuclear genetic lineages. Moreover, population genetic structures were mainly fixed through isolation by resistance. Multiple in situ refugia were identified by ecological niche models and high genetic diversity, which played crucial roles in the persistence and divergence of L. taliangensis during glacial-interglacial cycles. Dramatic climatic fluctuations further promoted recurrent isolation and admixing of populations in scattered glacial refugia. The apparent mitonuclear discordance was likely the result of introgression by secondary contact and/or female-biased dispersal. Postglacial expansion generated two major secondary contact zones (Ganluo (GL) and Chuhongjue (CHJ)). Identification of conservation management units and dispersal corridors offers important recommendations for the conservation of this species.

Paleoproductivity Proxies and Alkenone Precursors in the Western Mediterranean During the Early-Middle Pleistocene Transition

Paleoproductivity Proxies and Alkenone Precursors in the Western Mediterranean During the Early-Middle Pleistocene Transition

Amphibian body size and species richness as a proxy for primary productivity and climate: The Orce wetlands (Early Pleistocene, Guadix-Baza Basin, SE Spain)

Amphibians are considered excellent indicators of ecological and climatic changes with a remarkable phenotypic plasticity. The study of such adaptative capacities is central to understanding the climate and environmental changes that occurred during the Early-Middle Pleistocene Transition, at around 1.2 Ma, when the persistence of subtropical ecosystems in Europe came to an end, and several reptile and tree taxa were extirpated. The SE Spain sites in the Guadix-Baza Basin offer an exceptional opportunity for studying this change, in addition to the significant findings made in this area in the field of human evolution. We have analysed the body size of the most well-represented amphibian species in the sites, the Iberian waterfrog, Pelophylax perezi . In order to reconstruct past body sizes from fossil samples, a regression model from current osteological collections has been generated. Also, diversity of the herpetofauna community was studied at different levels as richness or species number. Finally, to study the relationships between body size, richness, climate and productivity, OLS regression models and Pearson correlations were applied. Also for this purpose, a productivity indicator was designed based on the addition of the two most productive ecosystems from previous habitat reconstruction. Amphibian body size appears to be negatively associated with primary productivity, reaching minimum values during the interglacial stages, when species richness increased. In contrast, during glacial periods characterised by greater aridity and fewer resources, amphibian body size increased while species richness decreased. Main explanations proposed to justify this pattern are the “water-availability hypothesis” and a trade-off between somatic growth and reproductive opportunities for females. The study of herpetofaunal diversity shows a clear correlation to regional plant diversity and primary productivity. The results of this work indicate that species richness and amphibian body size are valuable proxies that can complement current environmental and climate reconstruction methods. • Somatic growth and reproduction: the trade-off which determines amphibian body size. • Amphibian body size decreases towards more productive ecosystems. • Primary productivity determines species richness. • Frog body size is defined as a new indicator of Pleistocene ecosystem conditions.

Forest Steppe-Like Vegetation Near Cherskiy (West Beringia) During the Early Pleistocene Olyorian Period Reconstructed Using Plant Macrofossils

The lower Kolyma region is known for rich Early Olyorian large mammal assemblages including plesiomorphic musk ox, reindeer, horse, broad-fronted moose, steppe mammoth and cave bear. Data on the vegetation in zonal habitats from the Olyorian period are, in contrast, scarce. Earlier palynological results from classical Olyorian sites indicated predominant grassland vegetation with scattered larch occurrences but are, due to limited taxonomical resolution, uncertain. Plant macrofossil data were, so far, only available from azonal, aquatic habitats. Here, we describe Olyorian palaeo-vegetation from an exposure near Cherskiy, Nizhnekolymsky District, Sakha Republic, Russia. The macrofossil-based reconstruction of palaeo-vegetation revealed the existence of an open forest steppe comprising a mosaic of sparse larch groves in a dry grassland composed of tundra steppes, degraded meadow steppes and saline meadows. In the larch groves, light demanding shrubs and dwarf shrubs such as shrub birch (Betula cf. fruticosa, B. nana ssp. exilis), raspberry (Rubus idaeus), cowberry (Vaccinium vitis-idaea), and crowberry (Empetrum nigrum) formed the understory. Ruderal pioneer plants point to open ground as result of disturbances, possibly due to the activity of large herbivores. The nitrophytic ruderal species Urtica dioica, in particular, suggests locally increased nutrient supply from animal excretions. Also, the abundant remains of Chenopodium cf. prostratum might be explained by disturbances and nutrient enrichment, but Chenopodium is also characteristic of salt accumulation in the soil owing to high evaporation under arid conditions, which are also indicated by alkali grass (Puccinellia sp.). The presence of trees and shrubs indicates interglacial-like temperature conditions but the dominance of dry grassland species and the occurrence of facultatively halophytic plants (Chenopodium prostratum, Puccinellia sp.) suggests aridity, which is more typical of cold stages. During the early Pleistocene, i.e., prior to the Early-Middle Pleistocene transition (EMPT) culminating around 900 ka ago, the duration of climate cycles was shorter and the amplitude of climate fluctuations was smaller. Ice-rich permafrost formed only after the EMPT during increasingly extreme cold stages, and, during warm stages, its thawing resulted in paludification of the active layer. Prior to the EMPT, the climate in West Beringia was constantly relatively dry, more or less moderate and more stable than thereafter. In contrast to modern tundra and northern taiga in the study region, dry habitats apparently prevailed during the time of deposition of the plant macro-remains.

The extinction of the giant hyena Pachycrocuta brevirostris and a reappraisal of the Epivillafranchian and Galerian Hyaenidae in Europe: Faunal turnover during the Early–Middle Pleistocene Transition

The giant, short-faced hyena Pachycrocuta brevirostris was the largest Hyaenidae ever existed and the one that perfectly embodied the distinctive bone-cracking adaptations of this mammal family. Its dispersal into Europe is regarded as a biochronological marker of the Late Villafranchian at ∼2.0 Ma, and its potential ecological interactions with other carnivorans and early Homo populations diffusing Out of Africa have given rise to extensive discussions. Nevertheless, our comprehension of the extinction of P. brevirostris remains vague. Here, we first critically evaluate the European fossil record of the species and then we review the whole Epivillafranchian and Galerian Hyaenidae record, including P. brevirostris, Crocuta crocuta and “Hyaena” prisca. Biometric comparisons with other extinct and extant bone-cracking hyenas are carried out.In contrast to a common view, we recognize that there is neither evidence of a persistence of P. brevirostris beyond the Early-Middle Pleistocene boundary, nor of a coexistence between the giant hyena and C. crocuta. The replacement between the two species, which was also accompanied by the arrival of “H.” prisca, occurred at ∼0.8 Ma and can serve as a marker of the Epivillafranchian–Galerian turnover, part of the faunal renewal that reflects the response of mammal communities to the Early–Middle Pleistocene Transition. Moreover, we clarified that Pliocrocuta perrieri and “H.” prisca were different species, and that the latter was relatively more widespread than often assumed, being recorded from localities spanning in age almost the whole Middle Pleistocene and even the early Late Pleistocene.

1.36 million years of Mediterranean forest refugium dynamics in response to glacial–interglacial cycle strength

The sediment record from Lake Ohrid (Southwestern Balkans) represents the longest continuous lake archive in Europe, extending back to 1.36 Ma. We reconstruct the vegetation history based on pollen analysis of the DEEP core to reveal changes in vegetation cover and forest diversity during glacial-interglacial (G-IG) cycles and early basin development. The earliest lake phase saw a significantly different composition rich in relict tree taxa and few herbs. Subsequent establishment of a permanent steppic herb association around 1.2 Ma implies a threshold response to changes in moisture availability and temperature and gradual adjustment of the basin morphology. A change in the character of G-IG cycles during the Early-Middle Pleistocene Transition is reflected in the record by reorganization of the vegetation from obliquity- to eccentricity-paced cycles. Based on a quantitative analysis of tree taxa richness, the first large-scale decline in tree diversity occurred around 0.94 Ma. Subsequent variations in tree richness were largely driven by the amplitude and duration of G-IG cycles. Significant tree richness declines occurred in periods with abundant dry herb associations, pointing to aridity affecting tree population survival. Assessment of long-term legacy effects between global climate and regional vegetation change reveals a significant influence of cool interglacial conditions on subsequent glacial vegetation composition and diversity. This effect is contrary to observations at high latitudes, where glacial intensity is known to control subsequent interglacial vegetation, and the evidence demonstrates that the Lake Ohrid catchment functioned as a refugium for both thermophilous and temperate tree species.

Palaeoecological significances of deep-sea benthic foraminifera from Cascadia Margin, North East Pacific Ocean

The strong relationship between benthic foraminifera’s habitat and morphological characteristics to their surrounding environment are dominant component in marine community. This study attempts to understand the significance of benthic foraminifera in ecological importance and paleoceanographic reconstructions at Cascadia Margin, NE Pacific Ocean during the Pleistocene. The quantitative analyses of deep sea benthic foraminifera, particularly Bulimina exilis, Cibicides kullenbergi, Elphidium batialis, Epistominella exigua and Uvigerina proboscidea generally show higher abundances in the studied interval. The Gas Hydrate Stability Zone in the Cascadia Margin at ∼1200 ka to 162 ka (GHSZ; ∼240–70 mbsf) is related to low temperature and high-pressure conditions which are responsible for lower abundances of benthic foraminifera across that interval. The Alaska Current, North Pacific Current and California Current, also known as Eastern Boundary Currents (EBC), play a major role in the transportation of suspended sediments and coastal upwelling throughout the coast across the ∼650 to 450 ka and ∼35 to 2 ka intervals. The relative abundance rate of benthic foraminiferal community decreases with increasing core depth, indicating the influence of less ventilated and nutrient-enriched North Pacific Intermediate Water (NPIW). The present study also signifies the disappearance of benthic faunas throughout the Early–Middle Pleistocene Transition (EMPT, 1250–700 ka, Clark et al., 2006) period due to increased cyclic seasonality and decreased food supply, with few species (Bolivina alata, Bolivina spathulata, Cibicides wuellerstorfi, Epistominella exigua, Gavelinopsis lobatulus and Uvigerina peregrina) being exceptions.

A review on Bison schoetensacki and its closest relatives through the early-Middle Pleistocene transition: Insights from the Vallparadís Section (NE Iberian Peninsula) and other European localities

The evolutionary history of Bison is a matter of debate due to the scarcity of fossil remains from the earliest members of this clade and the close morphological similarities among species. To clarify the taxonomic status of the earliest stouter bison and their relationships to their putative ancestor, Leptobos, as well as other primitive forms traditionally referred to subgenus Bison (Eobison), we carry out a complete revision of the available European fossil record, with a focus on the forms occurring during the Early-Middle Pleistocene Transition. Emphasis is put on the description of the unpublished Bison remains from the Vallparadís Composite Section (VCS), including the sites of Cal Guardiola and Vallparadís Estació (Terrassa, NE Iberian Peninsula). VCS fossiliferous layers yielded one of the richest faunal assemblages from the European latest Early Pleistocene and one of the few European fossil sites covering almost entirely the Early-Middle Pleistocene Transition (1.2–0.6 Ma). The collection comprises thousands of ungulates remains, especially abundant fossils of a large Bison species. The morphology of the postcranial sample from VCS fits that of Bison (Bison) schoetensacki, i.e., the earliest stout bison (Bison s.s.) recorded in Europe. We studied more than 200 cranial and postcranial elements with a focus on the metapodial remains. Comparisons were performed with all the available fossil record of Pleistocene Eurasian fossil Bison species. We confirm the taxonomic validity of B. schoetensacki and recognize distinct eco-morphotypes of European bison between the late Early Pleistocene and the beginning of the Holocene based on the size and proportions of the metapodials. Although the appendicular skeleton shows reliable characters for the diagnosis of different species, the great morphological homogeneity recognized within the genus requires a cautious approach in systematic studies based on postcranial material.

New taxonomical, biochronological and palaeoenvironmental data from the Middle Pleistocene site of Cúllar de Baza 1 (Granada, Spain)

The intra-montane Guadix-Baza Basin is one of the few continental basins in Europe that hosts a well-dated set of fossiliferous sites spanning from the latest Miocene to the late Middle Pleistocene. The Cúllar de Baza 1 (CB-1) represents a key site to investigate the effects of the Early-Middle Pleistocene Transition, considered a fundamental transformation in the Earth’s climate state. Our review and update of the large mammal assemblage, and particularly equids, is of paramount relevance to understand the systematic affinities and the evolution of the Early and Middle Pleistocene European horses. We confirm the occurrence of two different taxa, the medium sized Equus altidens and the larger E. suessenbornensis. Moreover, we illustrate that CB-1 is essential for the biochronological studies of the latest Early Pleistocene/Middle Pleistocene transition (Epivillafranchian/Galerian ELMA); in particular with regard to the Last Occurrences of the Etruscan rhino Stephanorhinus etruscus and the large deer Megaloceros savini and the First Occurrence of the water-rat Arvicola mosbachensis in the Iberian peninsula. Finally, a development of a mosaic environment characterised the CB-1 site contrasting with the conditions reported for other Iberian late Early and Middle Pleistocene localities.

Early-Middle Pleistocene productivity changes of the Northern Cascadia Margin, Pacific Ocean

A total of 362 marine core samples from 200 meters below the sea-floor (mbsf) were examined through the International Ocean Drilling Program (IODP), Hole U1325B, Northern Cascadia Margin. The diversity parameters increased at ~200 mbsf during the Early Middle Pleistocene Transition (EMPT) period and gradually decreased towards ~165 mbsf. The diversity pattern is also notable, which projects the termination of EMPT due to increased orbital cyclicity (~41,000 to ~100,000 years). The δ18O (Uvigerina peregrina) at regular intervals ~150 mbsf, ~110 mbsf, ~50 mbsf and ~20 mbsf certainly agrees with the abundance of Cibicides wuellerstorfi, indicating the intrusion of California Cold Current in the region. The relative abundance rate of Cassidulina laevigata inversely proportional to the peaks of C. wuellerstorfi strongly indicating the circulation of Alaskan warm current in the Cascadia Margin. The paleoproductivity and oxygenation proxies strongly suggest the maximum primary productivity throughout ~85 mbsf towards the recent interval and the study region are showing oxic to suboxic environment further, the correlation matrix and the principal component phenomenon also strongly mirror the relationship and driving factors of the paleoceanographic condition. The present study aimed to understand the connections between each proxy liable to the paleoceanographic and paleoproductivity changes during the Early-Middle Pleistocene, Northern Cascadia Margin.