Quaternary Climate Change Research Articles

Spatial and climatic drivers of β‐diversity in assemblages of angiosperm genera across the world

Abstract β‐diversity quantifies the change in taxonomic and phylogenetic composition between areas. It can be partitioned into two additive components (turnover and nestedness). Geographic distance, which reflects dispersal limitation, and climatic distance, which reflects environmental filtering, are major drivers of β‐diversity, but few studies have assessed their relative importance to β‐diversity at a global scale. Here, we investigate the relationship of β‐diversity of angiosperm genera in regional floras worldwide to climatic conditions within regions and to geographic and climatic distances between regions. We found that (1) current climate has a stronger effect on phylogenetic turnover than does Quaternary climate change; (2) of the current climate variables examined, mean annual temperature is the strongest driver of phylogenetic turnover, followed by precipitation seasonality; (3) regions with high precipitation seasonality have high phylogenetic β‐diversity and phylogenetic turnover; and (4) at a global scale, the variation in phylogenetic turnover explained jointly by geographic and climatic distances is, on average, much larger than that explained uniquely by either distance, but that geographic distance explains more variation in phylogenetic turnover than climatic distance. Synthesis. These results reveal the synergistic role of geographic isolation and climatic filtering in determining the composition of floras worldwide, with less influence of Quaternary climate changes.

Precipitation variability and environmental change across late Quaternary glacial-interglacial cycles in lowland Central America: Insights from Lake Petén Itzá (Guatemala) sediments

Lowland Central America, a biodiversity hotspot in the northern Neotropics, is a region where the climate is influenced by the location and expansion-contraction of the Intertropical Convergence Zone (ITCZ) on seasonal to millennial timescales. Paleo-records from the Caribbean Sea and the eastern equatorial and subtropical Pacific Ocean illustrate the response of regional precipitation to fluctuations in global temperature, driven by glacial-interglacial cyclicity over the past 500 kyr. Here, we present a paleoclimate and paleoenvironment record from Lake Petén Itzá, lowland Guatemala, which spans the last ∼413 kyr. Sediment in the lake recorded lacustrine and terrestrial ecosystem responses to large-scale climate variability. Precipitation patterns during MIS11-9 (∼413-304 ka BP) align with the latitudinal position of the ITCZ, with superimposed effects from the strength of the Caribbean Low-Level Jet (CLLJ). A sediment hiatus, likely attributable to mass removal processes in the lake's shallower areas, spans the period from MIS8 (starting at 304 ka BP) to the end of MIS6 (at 149 ka BP). MIS6 was characterized by humid conditions, perhaps ascribable to a more southerly extension of cold fronts and intensification of the CLLJ. During MIS5, pronounced fluctuations among all sediment variables, accompanied by an abrupt decline in precipitation, may correspond with cold events inferred from North Atlantic Ocean sediment cores. Although discontinuous, the Lake Petén Itzá sediment record provides a window into late Quaternary climate and environmental change in lowland Central America.

Cicada minimum age tree: Cryptic speciation and exponentially increasing base substitution rates in recent geologic time

We developed a new time-calibrated tree incorporating primarily endemic along with some cryptic Ryukyu islands cicada data, following the recent publication of global cicada data by Marshall et al. (2018), Łukasik et al. (2018), Simon et al. (2019), Price et al. (2019), and Hill et al. (2021). A total of 352 specimens were analyzed using BEAST v1. X software with a relaxed clock model. Fossil calibrations as old as Triassic were adopted largely following Johnson et al. (2018) and Moulds (2018), and a Quaternary geological event calibration was adopted following Osozawa et al. (2012, 2021b) and input into BEAST v1. X. Our timetree suggests that Tettigarctidae had a cicada basal lineage as old as 200.63 Ma, with Derotettiginae the next oldest lineage at 99.2 Ma. Tibicininae is a sister of the remaining subfamilies of Tettigomyiinae, Cicadettinae, and Cicadidae, and their species level differentiation and radiation began at 40.57 Ma. The Cicadinae clade consists of specific tribes with paraphyletic relationship, and the vicariance and adaptive radiation generated many cryptic species in each tribe. We estimated base substitution rate as a function of age, and the result strongly indicates an exponential increase of base substitution rate in recent geologic time. The consequent increase in cicada biodiversity, including generation of cryptic species in the Ryukyu Islands and surroundings, may have been driven by the generation and spreading of C4 grasses and coeval Quaternary climate change.

The impact of climate on relief in the northern Japanese Alps within the past 1 Myr–The case of the Tateyama mountains

The impact of climate on mountain relief is often questioned, mainly due to the difficulties of measuring surface processes at the timescale of glacial-interglacial cycles. An appropriate setting for studying mountain erosion in response to Quaternary climate change is found in the Tateyama mountains in the Hida mountain range (northern Japanese Alps) due to distinct geomorphological features. The Japanese Alps uplifted within the past ∼1–3 Myr and experienced multiple glaciations during the late Quaternary. We use ultra-low temperature thermochronometers based on the luminescence of feldspar minerals from 19 rock samples and the electron spin resonance (ESR) of quartz minerals from 8 rock samples, in combination with inverse modelling to derive rock cooling rates and exhumation rate histories at 104–106 year timescales from three transects in the Tateyama region. While luminescence signals have already reached their upper dating limit, ESR signals (Al and Ti centres) yielded ESR ages of ∼0.3–1.1 Ma, implying surface processes active in the Pleistocene. Based on a negative age-elevation relationship, local relief reduction at a cirque-basin scale is identified over the past 1 Myr, whereas a positive age distribution with elevation for samples close to the mountain top does not follow this trend. Inverse modelling reveals rock cooling rates on the order of 20–70 °C/Myr, with slightly faster cooling for cirque-floor samples, which equate with erosion rates of 0.5–1 mm/yr that exceed rates from periglacial and slope processes in the same locality. Thus, our data suggest that Quaternary climate change coupled with distinct surface processes modified the slopes of the Tateyama mountains leading to a localised decrease in relief within an individual cirque basin over the second half of the Quaternary.

Global patterns of taxonomic and phylogenetic endemism in liverwort assemblages

Exploring the worldwide patterns of endemism and the processes that lead to the formation of high-endemism centers is crucial in biogeography. This study examines the geographic distribution and ecological influences on the endemism of liverworts across 390 regions worldwide. We assess phylogenetic endemism and relative phylogenetic endemism in relation to eleven environmental factors, which represent current and Quaternary climate variations, as well as topographic and environmental heterogeneity. Areas with higher endemism in liverworts tend to have higher temperatures, precipitation, and environmental heterogeneity, but lower temperature seasonality and lesser impacts from Quaternary climate changes. Regions exhibiting notably high endemism are predominantly found in tropical Asia, Madagascar, eastern Australia, and the Andes, while those with notably low endemism are generally in temperate Eurasia and North America, parts of Africa, and eastern South America. Centers of neo-endemism are mainly in southern Africa, whereas centers of paleo-endemism are in southern South America, tropical Asia, and New Zealand. Environment variability is a more significant predictor of phylogenetic endemism than current climate conditions, which are themselves more predictive than variables related to Quaternary climate changes. Nevertheless, these three types of explanatory variables combined explain only about one-third of the variance in phylogenetic endemism.

Glacial history of the King Haakon trough system, sub-Antarctic South Georgia

The glaciated island of South Georgia in the sub-Antarctic is a key area for climate reconstructions, because it is positioned in the Southern Ocean amidst the core belt of the Southern Westerlies and the main fronts of the Antarctic Circumpolar Current. This makes it particularly susceptible to changes in local, regional, but also Southern Hemisphere-wide climate conditions. Marine-geological records recovered from its continental shelf therefore offer unique potential to constrain how ice masses in this part of the Southern Ocean responded to Quaternary climate change, but despite this, little glacial-geomorphological and sedimentological research has been done offshore South Georgia. Here, we present a new suite of glacial landforms, identified from high-resolution bathymetry data, supplemented with acoustic facies from sub-bottom profiles, in order to reconstruct the pre-Holocene glacial history of the King Haakon Trough System on the southwestern South Georgia continental shelf. Our data show numerous landforms common for phases of ice advance and retreat, which are interpreted to document the confluence of two major trunk glaciers during peak glaciation. Progressively elongated linear bedforms imply accelerated ice flow and/or softer sediment substrate towards the shelf edge and suggest that the South Georgia Ice Cap experienced streaming ice and behaved similarly to other palaeo-ice sheets. A grounding-zone wedge close to the shelf edge marks the position of maximum ice extent during a peak glaciation, while clusters of recessional moraines and three large morainal banks indicate repeated phases of staggered retreat. Multiple extensive ice advances are indicated by stacked till sequences within the sub-bottom profiles of the mid- and outer shelf. The second-to-last till generation appears to be slightly more extensive than the most recent glacial till, and could suggest that South Georgia may have had a similar glacial evolution to other sub-Antarctic islands. This paper complements two studies focusing on the Holocene depositional environments and their associated sedimentary processes in the same trough system, in an effort to elucidate an important part of the Quaternary evolution of South Georgia's marine environment.

Geomorphological analysis of the Antinaco‐Los Colorados valley, La Rioja province, Argentina

AbstractThe Antinaco‐Los Colorados valley (ALCV) is a tectonic depression located in the centre‐north of the province of La Rioja (Argentina), limited to both the east and west by mountain ranges, in the broken foreland region. Geomorphological research on environmental dynamics is important for both building a reference framework for further studies and for the development of the socio‐economic activities in the area. This study presents the main geomorphological features of the tectonic depression at the regional scale in order to identify the primary factors involved in its evolution and the landforms it contains. The ALCV is asymmetric, and it is filled by up to 1600 m of sediments along the western margin. Using literature, images, digital elevation models of the study area and field work, different morphologies were identified in the valley, mostly linked to Quaternary climatic and tectonic changes. These morphologies were grouped into three main morphogenetic units that characterize this landscape: the relict piedmont levels, the current piedmont and the fluvial‐aeolian plain. The identification of fluvial forms suggests that fluvial systems have been important during the evolution of the landscape. Aeolian accumulation features, currently mostly vegetated, were likely formed under drier climatic conditions than those at present and probably related to the last ice age or even more recent times. Successive reactivations of the overall system are not only tectonic, as evidenced by the structural lineaments that affect relict piedmont levels and the fluvial‐aeolian plain, but also climatic. Thus, the identified landforms suggest that climatic and tectonic variables account for the variations in the environment of the ALCV, affecting the reaccommodation of the exogenous geomorphological processes and the modelling of the relief.

Moisture availability and groundwater recharge paced by orbital forcing over the past 750,000 years in the southwestern USA

Quaternary climate changes are driven in part by variations in the distribution and strength of insolation due to orbital parameters. Continental climate variability is well documented for the most recent glacial-interglacial cycles, yet few records extend further back in time. Such records are critically needed to comprehensively assess the entire spectrum of natural climate variability against the backdrop of anthropogenic warming. Here, we apply uranium isotope geochronology to calcite deposits to date groundwater-table changes in Devils Hole cave, Nevada. The deposits record multi-meter groundwater-table fluctuations over the last 750,000 years, reflecting the long-term evolution of hydroclimate in this presently arid region. During periods between glacial or interglacial extremes, the water table responded sensitively to variations in 65°N summer insolation, likely caused by the increasing extent of North American ice sheets during cold period, which steered moisture-laden trajectories towards the southwestern USA. These orbitally-driven hydroclimatic changes are superimposed on a tectonically-driven long-term decline in the regional groundwater table observed prior to 438,000 ± 14,000 years ago.

Soil‐vegetation interplay in a Holocene toposequence at Torres del Paine National Park, southern Andes, Chile

AbstractChile's Torres del Paine National Park (TPNP) is one of the most impressive landscapes in southern Patagonia, with unique natural elements on the edge of the southern ice field, where knowledge of soils and ecological relationships is nonexistent. Therefore, the objective of this study was to determine the chemical, physical, mineralogical, and micromorphological characteristics of Holocene soils along a local toposequence representing the main vegetation types of the TPNP. The morphological, chemical, physical, and mineralogical properties of 12 soil profiles were studied and classified according to Soil Taxonomy. Coevolution of vegetation and soil taxa is clearly evident since glaciation, with podsolization under austral Nothofagus pumilio forests leading to the development of spodosols, while paludization in local depressions with Nothofagus forests allowed the formation of histosols. Slopes covered with loess and tephra led to the formation of Andisols with shrub vegetation. Predominant parent materials include till from Late Quaternary advances of southern Andean ice, Pleistocene loess, and volcanic ash from surrounding Chilean volcanoes. The parent materials were strongly influenced by Late Quaternary climatic and landscape changes following the retreat of the Last Glacial Maximum in southern Patagonia, resulting in erosional and depositional conditions (windblown loess, fluvial glacial deposits, and moraines). Stable landforms show the influence of allochthonous volcanic ash shaping Andean features, combined with the accumulation of organic matter in hydromorphic soils. Three main groups of soils have been identified: loess‐rich soils, organic‐rich soils, and poorly developed soils. The latter show low fertility related to recent landforms on different substrates ranging from till, rocky slopes, talus, or glacial deposits. In high mountain regions under periglacial conditions, cryoturbation features indicate seasonal frost–thaw cycles without current permafrost. The diversity of soil orders in the mountains of southern Patagonia is comparable to similar environmental conditions and latitudes in the Northern Hemisphere. However, the andic properties due to volcanic ejecta inputs, as well as organic‐rich soils at low altitudes of bottom valleys, are typical features of the soils at TNTP.

The biogeographic and evolutionary processes shaping population divergence in Laupala.

Speciation generates biodiversity and the mechanisms involved are thought to vary across the tree of life and across environments. For example, well-studied adaptive radiations are thought to be fuelled by divergent ecological selection, but additionally are influenced heavily by biogeographic, genomic and demographic factors. Mechanisms of non-adaptive radiations, producing ecologically cryptic taxa, have been less well-studied but should likewise be influenced by these latter factors. Comparing among contexts can help pinpoint universal mechanisms and outcomes, especially if we integrate biogeographic, ecological and evolutionary processes. We investigate population divergence in the swordtail cricket Laupala cerasina, a wide-spread endemic on Hawai'i Island and one of 38 ecologically cryptic Laupala species. The nine sampled populations show striking population genetic structure at small spatio-temporal scales. The rapid differentiation among populations and species of Laupala shows that neither a specific geographical context nor ecological opportunity are pre-requisites for rapid divergence. Spatio-temporal patterns in population divergence, population size change, and gene flow are aligned with the chronosequence of the four volcanoes on which L. cerasina occurs and reveal the composite effects of geological dynamics and Quaternary climate change on population dynamics. Spatio-temporal patterns in genetic variation along the genome reveal the interplay of genetic and genomic architecture in shaping population divergence. In early phases of divergence, we find elevated differentiation in genomic regions harbouring mating song loci. In later stages of divergence, we find a signature of linked selection that interacts with recombination rate variation. Comparing our findings with recent work on complementary systems supports the conclusion that mostly universal factors influence the speciation process.

Temporal insights into karst system evolution: A case study of the unroofed cave above Škocjanske Jame, NW Dinarides

This study presents a comprehensive investigation of the unroofed cave above the active Škocjanske Jame water cave and explains the intricate processes that characterize the karst landscape. Despite extensive knowledge of the karst morphology, the precise development stages and timing of formation remained ambiguous. Through detailed multi-proxy sedimentary analyses, we unveil the sedimentary features documenting relict speleogenetic processes and provide insights into regional tectonic events and climatic changes. The cave was filled with two types of sediments: the upper speleothem section and the lower allogenic clastic section. Based on paleomagnetic characteristic and U/Th data, the fill of the unroofed cave is estimated to be between approximately 5 Ma (probably 5.2 to 4.9 Ma) and >773 ka old. Our results reveal a complex interplay of allogenic and autogenic sediments, suggesting a stable catchment over several million years. The dating results indicate deposition in phreatic regime since at least 5 Ma, with the river flowing through the cave until about 2.6 Ma. Our study emphasizes the importance of tectonically-driven uplift phases in cave speleogenesis rather than the importance of Quaternary climate changes. Furthermore, we define the initial stages of the development of the Škocjanske Jame karst system and estimate the time span of the evolution of solution and collapse dolines. This research underscores the importance of integrating geological, hydrological, and chronological approaches to unravel the history of karst landscapes and their implications for understanding dynamic karst processes. The temporal and spatial reconstruction of the development of the unroofed caves provides an insight into the first stages of the present karst system influenced by the sinking river.

Taxonomic and phylogenetic β‐diversity of regional assemblages of angiosperm species in relation to geographic and climatic determinants in Africa

AbstractAimBeta‐diversity quantifies the change in taxonomic and phylogenetic composition between areas, and is a scalar between local (α) and regional (γ) diversity. Geographic distance, which reflects dispersal limitation, and climatic distance, which reflects environmental filtering, are major drivers of β‐diversity. Here, we analyse a comprehensive data set of angiosperms in regional floras across Africa to assess the relationships of β‐diversity, and its components, to three major types of environmental variables (current climate, Quaternary climate change and topographic heterogeneity) thought to drive β‐diversity.LocationAfrica.TaxonAngiosperms.MethodsAfrica was divided into 27 regions. Species lists of angiosperms for each region were collated. The relationships of both taxonomic and phylogenetic β‐diversity, and their respective turnover and nestedness components, with geographic and environmental distances were assessed.ResultsThis study showed that (1) regions of the lowest β‐diversity are located in moist tropical climates, (2) the turnover and nestedness components of β‐diversity are negatively correlated with each other, (3) taxonomic β‐diversity is higher than phylogenetic β‐diversity across Africa, (4) variation in β‐diversity of angiosperms is more strongly associated with current climate than with Quaternary climate change and topographic heterogeneity and (5) the variation in taxonomic β‐diversity and its turnover component that is independently explained by geographic distance is much larger than that is independently explained by climatic distance for angiosperms in Africa.Main ConclusionsThe finding that geographic distance explained more variation than climatic distance suggests that dispersal limitation plays a greater role than environmental filtering in shaping angiosperm β‐diversity in Africa. Of climatic factors, current climate plays a more important role than Quaternary climate change in shaping angiosperm β‐diversity in Africa.

Quaternary tectonic and climatic forcing on the spatio-temporal evolution of the Meuse fluvial terrace staircase

The Quaternary is characterized by pronounced alterations between cold and warm climatic states, with the Mid-Pleistocene Transition marking a strong increase in the intensity of cold-climate conditions. River systems are sensitive to environmental perturbation (e.g., climate, tectonics, base level) and are expected to respond to such profound changes. This study uses a combination of terrace mapping and analysis of a dense borehole database to investigate the Meuse terrace staircase (and its deposits), and gain insight on how it reflects climatic and tectonic perturbations during the Quaternary. The lower reaches of the Meuse river, which has both its main water and sediment source in the Ardennes displays a well-developed terrace staircase that was sculpted mainly throughout the Quaternary. The staircase is located near the cities of Maastricht (southern Netherlands) and Liège (northwestern Belgium). About 30 terrace levels reflect signals of environmental perturbations in the lithological composition, gradients, thicknesses, and spatial distribution. The terraces are organized in groups, based on their morphological position, from old to young; these are the East Meuse terrace group and West Meuse High-, Middle- and Low terrace groups. Our findings show a consistent increase in the gravel content from older to younger terraces. The sandier composition of the deposits of the oldest terraces (Early Pleistocene) is closely related to the supply of the Miocene-Pliocene weathered material from the Ardennes. Younger terraces (Middle and Late Pleistocene) are much richer in gravel, evidencing sediment input from fresh or partially weathered bedrock. These changes point to a downstream migration of the gravel front throughout the Quaternary. The mean thickness of the terrace groups shows a slight increase, even though the same trend is not clear when each terrace is analyzed on an individual basis. The anomalous thickness of the Caberg 1 terrace suggests increased sediment input during the cold climatic conditions of the Elsterian (MIS 12), the first Quaternary glacial during which an ice sheet extended into the northern Netherlands. Reconstruction of terrace gradients reveals that older East Meuse terraces show a (reversed) gradient opposite to reconstructed palaeo flow directions, which is attributed to a combination of low gradients during terrace formation and footwall back-tilting of the Feldbiss Fault Zone. In our analysis we do not see clear evidence for the imprint of the Mid-Pleistocene Transition, which suggests that due to its gradual nature, its signal is either buffered or assimilated by the overall climatic signal of the Quaternary. This study offers a first complete temporal analysis of the Meuse terrace staircase, providing an important basis for better understanding the effects of Quaternary climatic change and tectonics, and their resulting effects in other river systems worldwide.

Globorotalia truncatulinoides as indicator of Subtropical Convergence and thermocline change during the late Quaternary in the Southeast Atlantic

Planktic foraminifera in biogenic sediments are widely applied as palaeoceanographic tools and the abundances of Globorotalia truncatulinoides have been used over the past few decades as indicators of upper water column changes over geologic time. The two morphological coiling directions of this species (sinistral and dextral) can provide valuable insight into how the upper water masses of the South Atlantic vary in response to climate change. This study aims to document and analyse the abundances of the planktic foraminiferal species G. truncatulinoides and its two morphological coiling directions in two cores from the continental slope of western South Africa at >3500 m water depth to assess the response of upper water masses to Quaternary climate change. The relative abundances of total G. truncatulinoides in the >125 μm size fraction, abundances of the dextral and sinistral forms in the >212 μm fraction and the division into further size fractions (212 μm, 250 μm, 300 μm, 355 μm, >400 μm) were analysed and considered to determine whether these abundances can be related to oceanographic regime shifts in the eastern South Atlantic during the late Pleistocene from MIS 6 to MIS 1. It was found that the Subtropical Convergence was located at a more southern location during MIS 5 and MIS 1, which allows for warmer subtropical species to increase in abundance with increasing Agulhas leakage around the southwestern margin. The thermocline is interpreted to have deepened during glacial terminations and interglacial periods when productivity was relatively lower and temperatures increased. The size fraction of the sinistral form in the >355 μm is dominant in MIS 5, MIS 3 and MIS1, indicating implications for the use of this species at certain size ranges. This study therefore indicates that G. truncatulinoides is a useful tracer of past Quaternary oceanographic changes along the western margin of South Africa, particularly when the coiling directions at the larger size fraction is taken into account.

Heavily eroded Pleistocene landscape and site-forming processes of the Acheulean artifacts-bearing Holocene sediments, Eastern Desert, Sudan

Since the Middle Pleistocene, the Sahara region has undergone strong environmental changes resulting from climate changes. Dry periods, constituting an ecological barrier to human presence, alternated with wet periods when the Sahara area was covered with green savanna and an extensive network of watercourses, allowing the area to be occupied by hunter-gatherer groups. Responding to the Quaternary climatic changes, hominin dispersal was channeled through vegetated corridors. Such evidence for human settlements connected to Pleistocene green corridors in the Sahara region has been discovered in the research area called EDAR (Eastern Desert Atbara River). This area comprises a cluster of Acheulean and Middle Stone Age (MSA) sites discovered in the fluvial sedimentary context. This manuscript discusses the occurrence of Middle Pleistocene Acheulean artifacts in much younger sediments documented at the site EDAR 6. These Acheulean artifacts are present within thick Holocene calcareous sandy silts formed between 2.7 ka and 8.7 ka based on an optically stimulated luminescence (OSL) chronology, which is also supported by paleomagnetic analysis. The stone gravelly artifacts mantled above the eolian deposits have been known in other Paleolithic sites under the desert environment of Northern Africa. We propose that the relocation of the Palaeolithic artifacts was due to long-lasting erosional and redepositional processes affecting the Acheulean artifacts-bearing sediments since the Middle Pleistocene. We interpret that the cumulative results of the two processes, i.e., the gravel framework dilation and the gravel overpassing, allowed the stone artifacts to be exposed at the surface or incorporated in the Holocene sediment layers.

Cicada minimum age tree: Cryptic speciation and exponentially increasing base substitution rates in recent geologic time

We developed a new time-calibrated tree incorporating primarily endemic along with some cryptic Ryukyu islands cicada data, following the recent publication of global cicada data by Marshall et al. (2018), Łukasik et al. (2018), Simon et al. (2019), Price et al. (2019), and Hill et al. (2021). A total of 352 specimens were analyzed using BEAST v1. X software with a relaxed clock model. Fossil calibrations as old as Triassic were adopted largely following Johnson et al. (2018) and Moulds (2018), and a Quaternary geological event calibration was adopted following Osozawa et al. (2012, 2021b) and input into BEAST v1. X. Our timetree suggests that Tettigarctidae had a cicada basal lineage as old as 200.63 Ma, with Derotettiginae the next oldest lineage at 99.2 Ma. Tibicininae is a sister of the remaining subfamilies of Tettigomyiinae, Cicadettinae, and Cicadidae, and their species level differentiation and radiation began at 40.57 Ma. The Cicadinae clade consists of specific tribes with paraphyletic relationship, and the vicariance and adaptive radiation generated many cryptic species in each tribe. We estimated base substitution rate as a function of age, and the result strongly indicates an exponential increase of base substitution rate in recent geologic time. The consequent increase in cicada biodiversity, including generation of cryptic species in the Ryukyu Islands and surroundings, may have been driven by the generation and spreading of C4 grasses and coeval Quaternary climate change.

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 fish. 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 and the emergence of cryptophthalmic phenotype in some endemic species. 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.

Czech Republic butterfly barcoding reveals that distribution of genetic lineages depends on species traits

AbstractAimThe distribution of within‐species lineages has been affected by Quaternary climate changes, and population differentiation has been influenced by species life history traits. We investigated whether the distribution of individual mitochondrial genetic lineages reflects the constituent species' traits. Using the functionally diverse group of butterflies, we examined which lineages are present in Central Europe, an important suture zone.LocationCzech Republic and Western Palearctic.TaxonA total of 140 butterfly species.MethodsWe sequenced DNA barcodes (cytochrome c oxidase 1) (959 sequences) of the entire Czech Republic butterfly fauna and used Barcoding of Life Data System to visualise the species' biogeographic patterns across Europe. We categorised the distribution patterns of lineages inhabiting the Czech Republic, and used multivariate statistics to interpret these categories by the butterflies' habitats, life history traits and threat levels.ResultsOpen habitat dwellers with specialist traits belonged to Eastern, Southern and temperate lineages. Habitat generalists and woodland dwellers belonged to the Western lineage, formed several lineages or displayed low genetic diversity; they often developed on woody plants, were large‐winged and had long flight periods. The most threatened species were the specialists of Southern, Eastern and temperate lineages.Main ConclusionsThe distribution of lineages in Central Europe reflects the history of Quaternary ecosystems: during cold periods of the Pleistocene, the diverse open habitats prevailed and species could expand westwards. Such species also suffer the most under the current anthropogenic habitat alteration. On the other hand, the mobile generalists and woodland dwellers expanded to Central Europe during the Holocene. Our approach of linking the distribution of lineages with species traits can be transferred to other study systems, and we show that DNA barcoding of under‐sampled areas represents a powerful tool for discovering the driving forces of biogeography.

The Last Glacial Maximum climate at Boomplaas Cave, South Africa

With a rich sequence of floral and faunal remains spanning the past >65,000 years, Boomplaas Cave is among the more important paleoenvironmental archives from South Africa's southern Cape. However, over the last several decades, its paleoenvironmental records have been the subject of conflicting interpretations, fueling uncertainty over fundamental aspects of Quaternary climate change in the region. Most significantly, researchers have variably interpreted the fossil plant and animal assemblages dating to the Last Glacial Maximum (LGM) as indicating harsh and arid or humid and productive conditions. This review critically examines the paleoenvironmental evidence from Boomplaas Cave, focusing on its LGM deposits and how they relate to the contentious problem of moisture availability through time. We show that interpretations of aridity during the LGM either (i) lack robust ecological links between the evidence and the paleoenvironmental interpretation, or (ii) are based on spurious patterns arising from sampling effects. In contrast, interpretations of relatively humid conditions during the LGM are grounded in present-day ecological observations and are consistent with both local and regional paleoenvironmental datasets. Overall, the evidence strongly supports the characterization of the LGM as a time of relatively humid conditions, with the transition to the Holocene characterized by increasing aridity. Several lines of evidence from Boomplaas Cave further suggest that this phase of increased humidity was associated with a dominance of winter rainfall, in contrast to the aseasonal rainfall regime that characterizes the southern Cape today.

Comparative phylogeography shows congruent co‐divergence in Neotropical seasonally dry forest and savanna tree species

AbstractAimThe response of South American seasonally dry tropical forest (SDTF) and savanna species to the Quaternary climate changes is still poorly understood. Here we use multi‐model inference approach to compare the phylogeography and demographic history of five trumpet tree species (also known as pau‐d'arco) and draw general biogeographical patterns: Handroanthus impetiginosus, H. ochraceus, H. serratifolius, Tabebuia aurea and T. roseoalba.LocationAmazonia, Atlantic Forest, Cerrado and Caatinga ecoregions, South America and Brazil.TaxaBignoniaceae, Tabebuia Alliance, trees.MethodsWe compiled genetic data, occurrence records and ecological niche modelling (ENM) from published articles. We used coalescent modelling to test patterns of co‐divergence, and analysed niche breadth and overlap and spatial patterns in genetic diversity using quantile regressions.ResultsSpecies showed concordant lineage divergence times in the Pleistocene. Lineage diversification and phylogeographical patterns are more related to species niche breadth than to biome (savanna or SDTF). Differences in genetic diversity among species matches the expected for the demographic scenarios obtained with coalescent simulations and ENMs: species with wider range expansion during the Last Glacial Maximum had higher diversity than species with range retraction or multiple refugia.Main ConclusionsDiversification burst in the Pliocene, and major diversification of lineages during the Pleistocene seems to be a general pattern in SDTF and savannas in the South America. The high number of haplotypes at the Central Brazil, corresponding to the Cerrado ecoregion, highlights the importance of Protected Areas for SDTFs and savannas, highly threatened biomes in Brazil.