Decoding loess geochemical signals of the Schwalbenberg – a key to terrestrial system response to millennial-timescale Upper Pleistocene climate changes in western central Europe

A multiproxy analysis of Hole 911A (Ocean Drilling Program (ODP) Leg 151) drilled on the Yermak Plateau (eastern Arctic Ocean) is used to investigate the behaviour of the Svalbard/Barents Sea ice sheet (SBIS) during late Pliocene and early Pleistocene (˜3.0–1.7 Ma) climate changes. Contemporary with the ‘Mid‐Pliocene (˜3 Ma) global warmth’ (MPGW), a warmer period lasting ˜300 kyr with seasonally ice‐free conditions in the marginal eastern Arctic Ocean is assumed to be an important regional moisture source, and possibly one decisive trigger for intensification of the Northern Hemisphere glaciation in the Svalbard/Barents Sea area at ˜2.7 Ma. An abrupt pulse of ice‐rafted debris (IRD) to the Yermak Plateau at ˜2.7 Ma reflects distinct melting of sediment‐laden icebergs derived from the SBIS and may indicate the protruding advance of the ice sheet onto the outer shelf. Spectral analysis of the total organic carbon (TOC) record being predominantly of terrigenous/fossil‐reworked origin indicates SBIS and possibly Scandinavian Ice Sheet response to incoming solar radiation at obliquity and precession periodicities. The strong variance in frequencies near the 41 kyr obliquity cycle between 2.7 and 1.7 Ma indicates, for the first time in the Arctic Ocean, a close relationship of SBIS growth and decay patterns to the Earth's orbital obliquity amplitudes, which dominated global ice volume variations during late Pliocene/early Pleistocene climate changes.

Millennial-scale terrestrial ecosystem responses to Upper Pleistocene climatic changes: 4D-reconstruction of the Schwalbenberg Loess-Palaeosol-Sequence (Middle Rhine Valley, Germany)

ABSTRACTPleistocene climatic fluctuations have significantly influenced biotic diversification globally, but their impacts on Neotropical insects remain understudied. Here, we evaluated the predictions of the Glacial and Interglacial Refugia models to investigate the effects of Pleistocene climate changes on four Sphenarium species: S. purpurascens, S. rugosum, S. variabile, and S. zapotecum. We analyzed phylogeographic patterns using a mitochondrial marker and conducted ecological niche and paleodistribution modeling to evaluate niche conservatism and historical distribution dynamics. We found high haplotype diversity (Hd > 0.87) and significant phylogeographic structure (NST–GST = 0.17–0.37) in all species except S. zapotecum, with non‐monophyly and limited haplotype sharing among S. purpurascens, S. variabile, and S. zapotecum. A few populations showed consistent changes in population size over time. Niche analyses rejected niche conservatism among species (overlap scores < 0.20; p ≥ 0.05) and minimal geographic overlap of suitable climatic areas since the Late Pleistocene. Climatic stability areas (i.e., potential refugia) cover less than 20% of the currently known distributions of S. purpurascens, S. zapotecum, and S. rugosum. Our findings suggest that Pleistocene climatic changes drove population divergence in Sphenarium grasshoppers; however, the impacts varied among species, and neither of the refugial models fully explained all patterns. The observed genetic differentiation, niche divergence, and demographic trends suggest recent differentiation, local adaptation, and complex evolutionary histories shaped by geography and climate. This study highlights the intricate interplay between environmental changes and evolutionary processes in shaping Neotropical insect diversity.

Widespread cyclic aridity during the Pleistocene is hypothesised to have had a significant impact on widespread Australian birds causing range-wide contractions to historical refugia and population differentiation while in isolation. In this study we tested a priori hypotheses for the impact of Pleistocene climatic and edaphic changes on the population history of the widespread Australian Pied Butcherbird (Cracticus nigrogularis). Analysis of mitochondrial DNA sequences from 55 individuals of C. nigrogularis revealed low genetic diversity, poor geographical structure and signatures of a recent demographic expansion. In contrast with long-standing biogeographical hypotheses, our data suggest that C. nigrogularis was likely to have been restricted to multiple refugia across its current range rather than undergoing range-wide contractions to one or few refugia. In addition, we found no evidence for the Carpentarian Barrier of northern Australia having limited dispersal in C. nigrogularis, which contrasts with predictions from intraspecific taxonomy and with population structures of several other bird species. Our data add to the increasing number of phylogeographical studies of widespread Australian birds that show evidence of maintaining large effective population sizes despite widespread aridity, as well as species-specific, rather than ecosystem-wide, responses to Pleistocene climatic changes and biogeographical barriers.

Pollen cores and plant and animal fossils suggest that global climate changes at the end of the last glacial period caused range expansions in organisms indigenous to the North American desert regions, but this suggestion has rarely been investigated from a population genetic perspective. In order to investigate the impact of Pleistocene climate changes and glacial/interglacial cycling on the distribution and population structure of animals in North American desert communities, biogeographical patterns in the flightless, warm-desert cactus beetles, Moneilema gigas and Moneilema armatum, were examined using mitochondrial DNA (mtDNA) sequence data from the cytochrome oxidase I (COI) gene. Gene tree relationships between haplotypes were inferred using parsimony, maximum-likelihood, and Bayesian analysis. Nested clade analysis and coalescent modelling using the programs mdiv and fluctuate were used to identify demographically independent populations, and to test the hypothesis that Pleistocene climate changes caused recent range expansions in these species. A sign test was used to evaluate the probability of observing concerted population growth across multiple, independent populations. The phylogeographical and nested clade analyses reveal a history of northward expansion in both of these species, as well as a history of past range fragmentation, followed by expansion from refugia. The coalescent analyses provide highly significant evidence for independent range expansions from multiple refugia, but also identify biogeographical patterns that predate the most recent glacial period. The results indicate that widespread desert environments are more ancient than has been suggested in the past.

Mountainous regions play a crucial role in shaping genetic differentiation among organisms. Climate change and topographical complexity are considered the most important processes influencing the diversification of these areas. In this study, we used Boana polytaenia treefrog species to assess how such biogeographical factors shaped its evolutionary history in the highly biodiverse Brazilian Atlantic Forest Mountain range, Serra do Mar and Serra da Mantiqueira. We investigated whether the patterns of genetic diversity of B. polytaenia along the mountains regions of the Southern Atlantic Forest were related to Pleistocene climate changes. Our dataset included mitochondrial and nuclear loci sequences from B. polytaenia, which we used to assess the genealogical relationships of lineages, population structure, lineages validation, changes in effective population sizes over time, time of divergence of lineages, climatic suitability through time with ecological niche modeling and whether niches of lineages are more or less similar than expected. The species exhibited two well-structured clades in each of the mountain chains, Serra da Mantiqueira and Serra do Mar. However, there was a lack of niche similarity and non-reciprocal geographic predictions for species distribution between the clades. Divergence between the clades occurred during the Pliocene/Pleistocene transition. We found contrasting responses to cooler periods on climatic suitability of lineages, with the expansion of suitable areas for B. polytaenia Serra da Mantiqueira Clade and retractions of climatically suitable areas for B. polytaenia Serra do Mar Clade. Despite clear differentiation, the sharing of nuclear haplotypes indicates retention of ancestral polymorphism, complicating the resolution of phylogenetic relationships in this species. Therefore, it is necessary to investigate the presence of more than one evolutionary unit in this dataset. Finally, Pleistocene climate changes influenced spatial distribution, leading to genetic variation in B. polytaenia species.

Although it has been suggested that Pleistocene climate changes drove population differentiation and speciation in many groups of organisms, population genetic evidence in support of this scenario has been ambiguous, and it has often been difficult to distinguish putative vicariance from simple isolation by distance. The sky island communities of the American Southwest present an ideal system in which to compare late Pleistocene range fragmentations documented by palaeoenvironmental studies with population genetic data from organisms within these communities. In order to elucidate the impact of Pleistocene climate fluctuations on these environments, biogeographic patterns in the flightless longhorn cactus beetle, Moneilema appressum were examined using mitochondrial DNA sequence data. Gene tree relationships between haplotypes were inferred using parsimony, maximum-likelihood, and Bayesian analysis. Nested clade analysis, Mantel tests, and coalescent modelling were employed to examine alternative biogeographic scenarios, and to test the hypothesis that Pleistocene climate changes drove population differentiation in this species. The program mdiv was used to estimate migration and divergence times between populations, and to measure the statistical support for isolation over ongoing migration. These analyses showed significant geographic structure in genetic relationships, and implicated topography as a key determinant of isolation. However, although the coalescent analyses suggested that a history of past habitat fragmentation underlies the observed geographic patterns, the nested clade analysis indicated that the pattern was consistent with isolation by distance. Estimated divergence times indicated that range fragmentation in M. appressum is considerably older than the end of the most recent glacial, but coincided with earlier interglacial warming events and with documented range expansions in other, desert-dwelling species of Moneilema.

Pleistocene climate changes were major historical events that impacted South American biodiversity. Although the effects of such changes are well-documented for several biomes, it is poorly known how these climate shifts affected the biodiversity of the Pantanal floodplain. Fish are one of the most diverse groups in the Pantanal floodplains and can be taken as a suitable biological model for reconstructing paleoenvironmental scenarios. To identify the effects of Pleistocene climate changes on Pantanal’s ichthyofauna, we used genetic data from multiple populations of a top-predator long-distance migratory fish, Salminus brasiliensis. We specifically investigated whether Pleistocene climate changes affected the demography of this species. If this was the case, we expected to find changes in population size over time. Thus, we assessed the genetic diversity of S. brasiliensis to trace the demographic history of nine populations from the Upper Paraguay basin, which includes the Pantanal floodplain, that form a single genetic group, employing approximate Bayesian computation (ABC) to test five scenarios: constant population, old expansion, old decline, old bottleneck following by recent expansion, and old expansion following by recent decline. Based on two mitochondrial DNA markers, our inferences from ABC analysis, the results of Bayesian skyline plot, the implications of star-like networks, and the patterns of genetic diversity (high haplotype diversity and low-to-moderate nucleotide diversity) indicated a sudden population expansion. ABC allowed us to make strong quantitative inferences about the demographic history of S. brasiliensis. We estimated a small ancestral population size that underwent a drastic fivefold expansion, probably associated with the colonization of newly formed habitats. The estimated time of this expansion was consistent with a humid and warm phase as inferred by speleothem growth phases and travertine records during Pleistocene interglacial periods. The strong concordance between our genetic inferences and this historical data could represent the first genetic record of a humid and warm phase in the Pantanal in the period since the Last Interglacial to 40 ka.

The Brazilian Atlantic Forest (BAF) is one of the most impacted biomes in the world, and in this region, there are several examples of the effects of Pleistocene climate changes among the species found there. Athenaea fasciculata (Solanaceae) is a forest component distributed mainly throughout the BAF extension. Here, we investigated the genetic diversity and population structure of A. fasciculata based on plastid and nuclear markers, aiming to better understand the impact of Pleistocene climate changes on BAF vegetation. We used population genetics, demographic methods and ecological niche modelling coupled to an evolutionary approach to describe the species distribution across time. The phylogeographic analysis of A. fasciculata indicated that Pleistocene climate changes played an important role in its evolution. The species is structured in two groups of populations that emerged from different refugia and were under different climate influences, supporting previously proposed connections between the Atlantic and Amazon Forests, the two most important Neotropical rainforests.

AimWe investigate the Plio‐Pleistocene evolutionary history of one of the most abundant rodents in Afrotropical forests. Specifically, we ask how their diversification was influenced by climate change, topography and major rivers.LocationTropical Africa: Lower Guinea (including Cameroon volcanic line; CVL), Congolia, Albertine Rift (AR), Kenyan highlands (KH).TaxonMurine rodents of the Praomys jacksoni complex.MethodsWe used 849 genotyped individuals to describe the overall diversity and spatial genetic structure across a majority of their known distribution area. The combination of one mitochondrial and three nuclear markers was used to infer dated phylogenies using Bayesian and maximum likelihood approaches. Genetic structure was further assessed by multispecies coalescent species delimitation. Current and past distributions of particular taxa were predicted using environmental niche modelling.ResultsThe complex is composed of five major genetic clades (proposed species). Two of them are restricted to specific habitat types (either montane forests of AR or wetlands in lowland forests along the Congo River), three others have wide geographic distributions and lower levels of ecological specialization. The earliest divergence is dated to the Plio‐Pleistocene boundary and is in accordance with the separation of AR forests and Guineo‐Congolian forests. Further diversification of the complex is associated with Pleistocene climate changes. Relatively stable refugia of suitable climatic conditions were identified in lowland Congolia (for two species currently distributed only in lowland forests) as well as in montane forests of CVL, AR, KH (playing the role of reservoirs of diversity). Large rivers, especially the Congo River, are important barriers to gene flow for most taxa, but probably were not the primary cause of differentiation.Main conclusionsThe evolutionary history of the complex was primarily affected by Pleistocene climate changes and diversification in forest refugia. There is little support for ecological parapatric speciation or the riverine barrier hypothesis.

Partamona seridoensis is an endemic stingless bee from the Caatinga, a Neotropical dry forest in northeastern Brazil. Like other stingless bees, this species plays an important ecological role as a pollinator. The aim of the present study was to investigate the genetic structure and evolutionary history of P. seridoensis across its current geographic range. Workers from 84 nests from 17 localities were analyzed for COI and Cytb genic regions. The population structure tests (Bayesian phylogenetic inference, AMOVA and haplotype network) consistently characterized two haplogroups (northwestern and eastern), with little gene flow between them, generating a high differentiation between them as well as among the populations within each haplogroup. The Mantel test revealed no isolation by distance. No evidence of a potential geographic barrier in the present that could explain the diversification between the P. seridoensis haplogroups was found. However, Pleistocene climatic changes may explain this differentiation, since the initial time for the P. seridoensis lineages diversification took place during the mid-Pleistocene, specifically the interglacial period, when the biota is presumed to have been more associated with dry conditions and had more restricted, fragmented geographical distribution. This event may have driven diversification by isolating the two haplogroups. Otherwise, the climatic changes in the late Pleistocene must not have drastically affected the population dynamics of P. seridoensis, since the Bayesian Skyline Plot did not reveal any substantial fluctuation in effective population size in either haplogroup. Considering its importance and the fact that it is an endemic bee from a very threatened Neotropical dry forest, the results herein could be useful to the development of conservation strategies for P. seridoensis.

Were the Late Pleistocene climatic changes responsible for the disappearance of the European spotted hyena populations? Hindcasting a species geographic distribution across time

Droughts in Western Central Europe (WCE) have recently attracted attention due to their detrimental impact on crops, ecosystems, and society, as evidenced by events in 2018 and 2022. In this region, however, their variability and underlying causes remain unclear. This study aims to associate droughts with the atmospheric circulation to gain insight into their drivers. We employed reanalysis datasets (ERA5, 20CRv3, and ModE-RA) to identify meteorological drought events using the Standardized Precipitation Evapotranspiration Index at a 3-month scale and consistently connect them to atmospheric circulation patterns through k-means clustering. The three datasets are evaluated over the WCE regions, showing that they are highly reliable over periods ranging from 70 to 180 years, providing a long perspective on the recent events. Firstly, we demonstrate that droughts in WCE display a strong multidecadal variability with no significant long-term trend. Although precipitation has increased over time, this has been offset by the rising atmospheric evaporative demand due to warming. Secondly, we identify three distinct atmospheric circulation patterns associated with drought events in WCE: a high-anomaly geopotential height centred over Western Central Europe (WCE+); a dipole of high-anomaly geopotential height over the British Isles and low-anomaly geopotential height over the Maghreb (BIM+); and the negative phase of the North Atlantic Oscillation (NAO-), predominantly in winter. Our analysis shows that droughts have become increasingly associated with WCE+ over the last century, while their association with NAO- has decreased over the past 180 years. This research provides a regional historical analysis of meteorological drought and its drivers, offering better insight into long-term regional climate change.

Organisms living in arid biomes are predicted to be at threat of extinction associated with ongoing climatic and anthropogenic change. Our understanding of species responses to Pleistocene climatic changes within these environments is still limited, particularly in Australia. Here we evaluate the demographic and evolutionary history of a widespread Australian marsupial, the black-footed rock-wallaby (Petrogale lateralis) whose contemporary distribution is highly fragmented across the arid biome and offshore islands. Combining genomic data from historical and modern samples we evaluate the divergence history of the five P. lateralis sub-species. The species has experienced a Pleistocene demographic expansion across the vast Australian arid biome, with subsequent fragmentation of populations and sub-species. Populations of the widespread sub-species P. lateralis lateralis are as divergent as sub-species within P. lateralis and there is negligible recent gene flow between most populations/sub-species. Individuals on islands have extremely low genetic diversity and high inbreeding coefficients, in contrast to the naturally fragmented mainland populations. Our results indicate historical connectivity of populations ~160-640 kya, and indications of bottlenecks for both island and some isolated mainland populations, providing important context for conservation management and potential genetic rescue. However, given the large ecological gradient and chromosomal variation within this widespread species, assessment of ecological differences will be important before decisions to mix across geographically distant populations and/or sub-species.

We performed phylogeographic and genetic structure analyses of Neothraupis fasciata joined with species distribution modelling to evaluate whether: (1) the distribution of genetic variability shows a pattern expected by the isolation-by-distance model; (2) the influence of the Pleistocene climate changes on species distribution; and (3) climate/climatic stability (hypothesis of climatic stability) as a predictor of population genetic diversity. Based on two molecular datasets (ND2 and FIB-5), the isolation-by-distance hypothesis was not supported. The mitochondrial haplotype network indicated the existence of historically isolated populations at the southern range of the species distribution, and recent population expansion was identified by both neutrality tests and extended Bayesian skyline plot analysis. Thus, the climatic changes during the Pleistocene might have promoted the reconnection of the partially isolated southern populations, which may have persisted in the plateaus during the cycles of savanna contractions. Subsequently, this species (re)colonized northern areas of the species present distribution, following the continuous vegetation on the São Francisco and Central plateaus about 60 kyr, and also reached the Amazonian savannas likely via the central corridor. Thus, our results indicated that the intrinsic relationship between the relief heterogeneity (plateaus and depressions) and the climatic fluctuations, mainly in the Pleistocene, promoted population reconnection and demographic expansion of N. fasciata.