Past Environments Research Articles

Leaf Wax Lipid Extraction for Archaeological Applications.

Plant wax lipid molecules, chiefly normal (n-) alkanes and n-alkanoic acids, are frequently used as proxies for understanding paleoenvironmental and paleoclimatic change. These are regularly analyzed from marine and lake sediments and even more frequently in archaeological contexts, enabling the reconstruction of past environments in direct association with records of past human behavior. Carbon and hydrogen isotope measurements of these compounds are used to trace plant type and water-use efficiency, relative paleotemperature, precipitation, evapotranspiration of leaf and soil moisture, and other physiological and ecological parameters. Plant wax lipids have great potential for answering questions related to human-environment interactions, being for the most part chemically inert and easily recoverable in terrestrial sediments, including those dating back millions of years. The growing use of this technique, and comparison of such data with other paleoenvironmental proxies such as pollen and phytolith analysis and soil carbonate and tooth enamel isotope records, make it essential to establish consistent, best-practice protocols for extracting n-alkanes and n-alkanoic acids from archaeological sediments to provide comparable information for interpreting past climatic, ecosystem, and hydrological changes and their interaction with human societies. © 2020 The Authors. Basic Protocol 1: Total lipid extraction Support Protocol 1: Weighing the total lipid extract Support Protocol 2: Cleaning the PSE extraction cells Alternate Protocol 1: Soxhlet total lipid extraction Alternate Protocol 2: Ultrasonic total lipid extraction Basic Protocol 2: Separation of lipids by aminopropyl column chromatography Basic Protocol 3: Separation of lipids by silver-nitrate-infused silica gel column chromatography Support Protocol 3: Preparation of silica gel infused with 10% silver nitrate Basic Protocol 4: Methylation of n-alkanoic acids Basic Protocol 5: Gas chromatography mass spectrometry (GC-MS) Basic Protocol 6: Gas chromatography isotope ratio mass spectrometry (GC-IRMS).

The impact of diffusive transport of methane on pore-water and sediment geochemistry constrained by authigenic enrichments of carbon, sulfur, and trace elements: A case study from the Shenhu area of the South China Sea

Sulfate-driven anaerobic oxidation of methane (SD-AOM) controls methane release from marine sediments to the ocean. A variety of authigenic precipitates within sediments has been widely used to identify past occurrences of SD-AOM. However, the lack of a systematic evaluation of the formation conditions of these precipitates sometimes impedes the recognition of SD-AOM in past environments characterized by diffusive transport of methane. Carbon, sulfur, and trace element geochemistry of pore-water and sediments was investigated at a site affected by upward methane diffusion in the Shenhu area of the South China Sea. Here, the sulfate-methane transition zone (SMTZ) is located ~7.6 m below the seafloor based on sulfate and methane concentrations. The slope of δ34S vs. δ18O values of sulfate is consistent with diffusive transport of methane. Concentration and isotope profiles of pore-water species point to diffusive rather than advective transport of solutes. Enhanced sulfate reduction inferred from δ34S values of sulfate agrees with the local occurrence of relatively abundant, 34S-enriched iron sulfide minerals. The time required to produce the observed authigenic iron sulfides around the SMTZ is estimated to be ~1.1 ka based on the amount of iron sulfide minerals and the present diffusive flux of sulfate. No enrichment of authigenic carbonate, barium (Ba), and molybdenum (Mo) was detected in the studied sediments. This observation is consistent with the calculation that the current fluxes of pore-water calcium, magnesium, Ba, and Mo are too low to allow for authigenic enrichments. The low fluxes are largely controlled by diffusion, which facilitates the formation of 34S-enriched iron sulfide minerals. The observed enrichment patterns – unlike those of sediments affected by advective seepage – are expected to be prevalent in modern and ancient continental-margin sediments, and may contribute to the identification of past methane-rich zones and overlying SD-AOM zones as sinks for methane in the geological record.

Location Decisions of New Manufacturing Firms in Ecuador. Agglomeration Mechanisms

This investigation seeks to explore the importance of agglomeration mechanisms in the location decisions of new manufacturing firms in Ecuador, based on sector and canton level data for the 2000–2010 period. A model is proposed to explore the relative importance of agglomeration mechanisms in location decisions of new manufacturing companies, a regression is performed using instrumental variables, the econometric estimation is developed, and an identification strategy is proposed. The results of the empirical analysis show that the learning mechanism, and history, have a positive and significant impact on the creation of new firms. An increase of 1% in the transfer of knowledge in the industries and cantons of the country is correlated with the increase in the location of new firms in the order of 9.2%. In turn, history has a positive and significant effect on the creation of new firms, in industries and cantons characterized by a past industrial environment. Even when the learning mechanism and history are controlled by provinces, sectors, and cantons, they continue to be the most important determinants of the location of new firms. This evidence could be attributed to the public investment in Ecuadorian industry in recent years. In this sense, the contribution of this work is found in the empirical distinction of the mechanism that favors or inhibits the location decisions of new companies. The analysis was replicated for a three-digit sectorial disaggregation level, to verify whether the agglomeration mechanisms operate differently on a different industrial scale. The results suggested that there were no differences to be considered. When the analysis was done excluding the cantons of Quito, Guayaquil, and Cuenca, given their high representation in terms of the birth of industries and employment, the results were consistent with those previously mentioned. However, it is so only with respect to history, which in this case accounts for 38.8% of the birth of firms; whereas, matching accounts for an order of 38.9% in the period of analysis. This result is explained in the context of the country’s industrial policy.

Losing my loss aversion: The effects of current and past environment on the relative sensitivity to losses and gains

It is often assumed that most people are loss averse, placing more weight on losses than commensurate gains; however, some research identifies variability in loss sensitivity that reflects features of the environment. We examined this plasticity in loss sensitivity by manipulating the size and distribution of possible outcomes in a set of mixed gambles, and assessing individual stability in loss sensitivity. In each of two sessions, participants made accept-reject decisions for 64 mixed-outcome gambles. Participants were randomly assigned to conditions defined by the relative range of losses and gains (wider range of losses vs. wider range of gains), and the currency-units at stake (‘pennies’ vs. ‘pounds’). Participants showed modest but non-trivial consistency in their sensitivity to losses; though loss sensitivity also varied substantially with our manipulations. When possible gains had greater range than possible losses, most participants were loss averse; however, when possible losses had the greater range, reverse loss aversion was the norm (i.e., more weight on gains than losses). This is consistent with decision-by-sampling theory, whereby an outcome’s rank within a consideration-set determines its value, but can also be explained by the gamble’s expected-value rank within the decision-set, or by adapting aspirations to the decision-environment. Loss aversion was also reduced in the second session of decisions when the stakes had been higher in the previous session. This illustrates the influence of prior context on current sensitivity to losses, and suggests a role for idiosyncratic experiences in the development of individual differences in loss sensitivity.

Forward and inverse methods for extracting climate and diet information from stable isotope profiles in proboscidean molars

Intratooth stable isotope profiles in enamel provide time series of dietary and environmental information that if correctly interpreted, serve as archives of seasonal variability in past environments. A major challenge in interpreting these profiles arises from time averaging imparted by enamel mineralization and developmental geometry, whereby the primary (δ13C or δ18O) input signal is attenuated and shifted, which can potentially lead to incorrect interpretations of the magnitude or frequency of seasonal variability. Several forward and inverse models have been developed to reconstruct the primary input signal from intratooth profiles in continuously growing teeth. Here the models developed by Passey and Cerling (2002) and Passey et al. (2005) are extended to molars of Elephantinae, which grow over a long but finite interval of time. Proboscidean molars are particularly attractive for intratooth profiles because they may contain a decade or more of information and they are often well preserved in the fossil record because of their thick enamel and large size.Forward model parameters are established using histological analysis of molar thin sections of extant African elephants (Loxodonta africana) and a mammoth (Mammuthus columbi) and by micro-CT analysis of L. africana molar plates. The density of immature enamel is about 65% of the final density of mature enamel. The appositional length varies from approximately 35 to 55 mm, and the maturation length is about 70 mm. Histological methods are used to determine crown formation time (CFT) in elephant and mammoth molar plates. CFT for the elephant and mammoth molar plates studied in thin section are about 5–6 years and 11 years, which translate to mean growth rates of about 21 mm/year and 16 mm/year, respectively.Coeval molar and tusk profiles from a zoo elephant are compared. The tusk isotope profile serves as a proxy for the primary input signal, and thus provides an opportunity to evaluate the forward and inverse models. The results from the zoo elephant profiles demonstrate that the inverse model accurately reconstructs the amplitude and overall structure of the primary input signal. Inverse model results of mammoth molar profiles show double the range of δ13C in measured enamel profiles. Inversion model results illustrate that improved reconstruction of the primary input signal can lead to more accurate interpretations of the seasonal variability of diet and body water and by extension, vegetation and precipitation in past environments.

When less is more: Element selection as sampling strategy in zooarchaeology

Zooarchaeologists make a range of analytical decisions that affect taxonomic identifications, measures of abundance, and, by extension, socio-environmental interpretations. One decision that is often not documented and/or justified is the question of which skeletal elements, or element fragments, should be identified. This situation is especially concerning for, but not limited to, zooarchaeological analysis of fish remains, as ichthyoarchaeologists have historically adopted varied approaches to element selection for taxonomic identification, ranging from identification of a few distinctive jaw elements to attempted identifications for all elements. Here, we argue the process of element selection should be approached more intentionally as a sampling issue, which would provide a framework for evaluating whether identified samples are representative of the recovered assemblages from which they derive, and potentially improve the efficiency of analysis. We use nestedness analysis and sampling to redundancy to illustrate the effects of element selection on taxonomic richness and relative abundances in fishbone assemblages from three cultural and biogeographic regions: the northeast Pacific, the Hawaiian Islands, and Aotearoa New Zealand. We find that both methods are effective for evaluating the representativeness of identified assemblages based on varied element sets, and our results demonstrate that, in many assemblages, identifying all elements provides redundant information about taxonomic representation (richness and relative abundance). In such cases, one could select fewer elements for identification and spend more time examining remains from additional parts of a site or carrying out specialized analyses, which would provide new insights about past environments or human-animal relationships. The proposed analytical strategy aims to help zooarchaeologists justify and make informed decisions about how many and which specific elements to include in any given analysis. Our study adds to the growing discourse on best practices in zooarchaeology.

Glacial-interglacial transitions in microbiomes recorded in deep-sea sediments from the western equatorial Atlantic

In the late Quaternary, glacial-interglacial transitions are marked by major environmental changes. Glacial periods in the western equatorial Atlantic (WEA) are characterized by high continental terrigenous input, which increases the proportion of terrestrial organic matter (e.g. lignin, alkanes), nutrients (e.g. iron and sulphur), and lower primary productivity. On the other hand, interglacials are characterized by lower continental contribution and maxima in primary productivity. Microbes can serve as biosensors of past conditions, but scarce information is available on deep-sea sediments in the WEA. The hypothesis put forward in this study is that past changes in climate conditions modulated the taxonomic/functional composition of microbes from deep sediment layers. To address this hypothesis, we collected samples from a marine sediment core located in the WEA, which covered the last 130 kyr. This region is influenced by the presence of the Amazon River plume, which outputs dissolved and particulate nutrients in vast oceanic regions, as well as the Parnaiba river plume. Core GL-1248 was analysed by shotgun metagenomics and geochemical analyses (alkane, lignin, perylene, sulphur). Two clusters (glacial and interglacial-deglacial) were found based on taxonomic and functional profiles of metagenomes. The interglacial period had a higher abundance of genes belonging to several sub-systems (e.g. DNA, RNA metabolism, cell division, chemotaxis, and respiration) that are consistent with a past environment with enhanced primary productivity. On the other hand, the abundance of Alcanivorax, Marinobacter, Kangiella and aromatic compounds that may serve as energy sources for these bacteria were higher in the glacial. The glacial period was enriched in genes for the metabolism of aromatic compounds, lipids, isoprenoids, iron, and Sulphur, consistent with enhanced fluvial input during the last glacial period. In contrast, interglacials have increased contents of more labile materials originating from phytoplankton (e.g. Prochlorococcus). This study provides new insights into the microbiome as climatic archives at geological timescales.

Paleoenvironmental interpretations of Irati and Mangrullo Formations (Permian of Paraná Basin) based on rocks and fossil bones through spectroscopy techniques

The hydroxyapatite of fossil bones can provide paleoenvironmental information, because throughout the fossil-diagenetic process, the fossils can incorporate elements from the sedimentary rocks that involved them. In this way, the present study aimed for geochemical patterns in mesosaurid bones and their respective host rocks to project the paleoenvironmental conditions at deposition/diagenesis’ time. For this purpose, Raman Spectroscopy and X-Ray Fluorescence analysis were performed. The samples came from Irati (S1 – São Matues do Sul, S2 – Assistência, S4 – Aceguá e S5 – São Gabriel) and Mangrullo (S3 – Uruguay) Formations. We found similar geochemical composition between S1 and S5; S3 and S4 which also indicates a similar paleoenvironmental context. The samples S1 and S5 have relatively high Al, Si and Sr contents which can represent acidic conditions and high depths. The second set (S3 and S4) have similar contents of Al, Si and Ca, but it is worth to note that the Si and Ca contents are slightly different. The Si and Ca contents suggest that S3 was slightly deeper and less acidic when compared to S4. In general, the first set (S1 and S5) were deeper and more acidic than the second (S3 and S4). The S2 sample is out of line with the others, corresponding to shallow or coastal and more basic paleoenvironment. Overall, our results agree with previous studies about the past environment where mesosaurs lived. Also, shows that spectroscopy techniques are reliable and should be used to refine paleoenvironmental interpretations.

Holocene development and human use of mangroves and limestone forest at an ancient hong lagoon in the Tràng An karst, Ninh Binh, Vietnam

How past environments and communities responded to episodes of coastal inundation can inform preparations for future resilience to predicted rises in sea level. Southeast Asia’s extensive coastlines and expanding coastal populations mean vast natural and human capital is at risk from future sea level rise. Regional mangroves provide many ecosystem services that can help mitigate such risks, but deforestation has left them threatened and compromised. The present study examines the Holocene development and human use of mangrove forest in northern Vietnam, where existing palaeo-records derive from sedimentary archives in tidal flat, estuarine and deltaic settings. Here, we expand that coverage by describing conditions at an enclosed doline within the Tràng An limestone karst in Ninh Binh province that would have been sheltered from deltaic and marine processes. We present a multi-proxy assessment incorporating pollen analysis of the 8125-year-old discontinuous sediment core obtained from the doline floor, combined with inferences from erosional tidal notches in the enclosing limestone, and analyses of phytolith, vertebrate and mollusc assemblages from an adjacent archaeological cave site with deposits of comparable age. The results provide a detailed example of how enclosed coastal environments and communities responded to Middle Holocene marine inundation. High percentages of pollen from mangroves (17–57%) suggest their colonisation of the doline from ∼8100 cal. BP and persistence until ∼250 cal. BP, well after the intertidal zone regressed seaward beyond the massif. Archaeological assemblages dating to ∼5500 cal. BP and containing palm and woody eudicot phytoliths and sponge spicules, neurocrania of the fish genus Pomadasys (‘grunts’, ‘grunters’ or ‘javelins’) and brackish-water molluscs Sermyla riqueti and Neripteron violaceum support the persistence of mangrove environments through the Middle Holocene high-stand, a period of hiatus within the core, and indicate human foraging and fishing activities took place in mangrove and lagoonal habitats alongside hunting in the surrounding limestone forest. Subsequent structural opening of this latter forest formation from ∼1075 cal. BP (875 CE), evident in the pollen record, coincides with the Medieval Climate Anomaly and with the adjacent development of the ancient capital at Hoa Lu. We propose that given the long-term persistence of mangrove habitats and associated resources documented in this study, regional initiatives aimed at rehabilitating mangroves (with the positive consequences that this holds for biodiversity and socio-economic conditions) may wish to consider selective restorative measures within Tràng An and similar sheltered sub-coastal karst settings.

Late Pleistocene meso-megaherbivores from Brazilian Intertropical Region: isotopic diet (δ 13C), niche differentiation, guilds and paleoenvironmental reconstruction (δ 13C, δ 18O)

ABSTRACT Stable isotopes in enamel, dentin, and bone hydroxyapatite are an important tool in the investigation of the palaeoecology of extinct organisms and are applied as proxies for different environmental parameters (e.g. diet, temperature, guild) that assist in reconstitutions of past environments. Tooth and bone samples of late Pleistocene Toxodon platensis, Eremotherium laurillardi, Notiomastodon platensis, Glyptotherium sp., Hippidion principale, Xenorhinotherium bahiense and Nothrotherium maquinense from several localities in Brazilian Intertropical Region, had δ 13C and δ 18O analysed to infer their paleodiet, guild and niche breadth that allow a reconstruction of past environment in which they lived. Including isotopic data for the horse Equus (Amerhippus) neogeus, the giant lama Palaeolama major, the Cingulatas Panochthus sp. and Holmesina paulacoutoi, and the giant ground sloth Valgipes bucklandi, we can suggest that the Brazilian Intertropical Region presented three guilds: browsers (N. maquinense, V. bucklandi, X. bahiense), mixed-feeders (H. principale, E. laurillardi, T. platensis, N. platensis, P. major, Panochthus sp., H. paulacoutoi) and grazer (E. (A.) neogeus, Glyptotherium sp.). These results indicate a dry environment with mixed vegetation with a predominance of open savanna, suggesting that the area at the time was similar to the current in more arid and open areas of the shrub savanna.

Ancient DNA preservation, genetic diversity and biogeography: A study of houseflies from Roman Qasr Ibrim, lower Nubia, Egypt

The optimal preservation of many Egyptian archaeological sites provides unique opportunities in the research into the evolution of synanthropic species, wild animals or plants, which benefit from close association with man-made human habitats. In this study we extracted and analysed ancient mitochondrial DNA (mtDNA) from three synanthropic insect species, two storage pests, Sitophilus granarius (Coleoptera: Curculionidae) (N = 8) and Trogoderma granarium (Coleoptera: Dermestidae) (N = 14), and the housefly Musca domestica (Diptera: Muscidae), (N = 14), from Roman Qasr Ibrim, an Egyptian frontier site located in lower Nubia. The impact of different experimental variables on ancient DNA recovery was also evaluated, confirming that it is possible to extract endogenous ancient DNA from desiccated specimens while preserving the insect exoskeleton. A phylogenetic comparison of the Qasr Ibrim housefly mtDNA-COI (COI) with modern housefly sequences, revealed that they were genetically similar to modern Egyptian, Near Eastern, Indian, Japanese, and US/Canadian populations. As the now cosmopolitan houseflies were transported by human populations alongside domestic animals and crops and may have aided the spread of disease, these findings provide important information for these processes. While limited by the resolution of the comparative databases, our research suggests the existence of biological invasions and links across the Red Sea from Egypt to the Arabian Peninsula, and exchanges between India and Egypt. We demonstrate the great potential of fossil insect aDNA for reconstructing biogeographic and diachronic species distribution and for better understanding past environments.

Lithological correction of chemical weathering proxies based on K, Rb, and Mg contents for isolation of orbital signals in clastic sedimentary archives

The extraction of palaeoenvironmental (palaeoclimatic) signals from the chemical composition of siliciclastic sediments is valuable for the reconstruction of past environments, particularly in continental basins. Here we test novel weathering proxies, which are less sensitive to lithological control than the previously used raw element ratios K/Al, K/Ti, and K/Rb: (1) local enrichment factors of K/Al, Mg/Al, and K/Rb, i.e., the element ratios corrected for grain size- and matrix composition using local background functions (Al/Si, Fe, and Ca as explanatory variables) and ordinary regression and (2) robust regression residuals of those element ratios based on isometric log-ratio coordinates of the most relevant “lithogenic” elements (Ca, Fe, Rb, Si, Zr) in the chemical composition. Chemical weathering proxies can be obtained from departures of chemical composition of sedimentary profiles from relationships with other chemical elements, in particular those with grain-size control. The resulting weathering proxies were examined for the Miocene deposits from the Most Basin, the Czech Republic, which recorded one of the major warm episodes of the Cenozoic time – the Miocene Climatic Optimum. The performance of weathering proxies has been checked by (1) comparison of individual proposed proxies in one drill core HK930, (2) detailed analysis of orbital signals in the relevant compositional functions in HK930; and (3) lateral correlation of three cores HK930, DU7, and DO565 of the same basin. The novel proxies show lateral stability and orbital signatures of short eccentricity, obliquity, and precession, confirming their usefulness in palaeoenvironmental studies. Corrections for grain-size and carbonate contents should help to isolate climatic content from the weathering proxies, although in the studied sediments it weakened the precession component in the orbital signal, as grain-size proxies and other compositional data also carried orbital signals. We propose to consider these proxy ideas in palaeoclimatic reconstructions based on chemical weathering proxies.

Experimental formation of clay-coated sand grains using diatom biofilm exopolymers

Abstract In sedimentary environments, clay and sand are segregated by hydrodynamic processes. Yet, clay coats, thin clay envelopes lining sand grains, are abundant in modern and ancient coastal sedimentary deposits. Here, we present laboratory experiments in which we produced clay-coated quartz sands similar to those observed in modern and ancient estuarine sands. These coats were produced at ambient temperature by mixing exopolymeric substances (EPS) derived from intertidal diatom biofilms with clay minerals and quartz reference materials. The imaging of sediment-EPS mixes using cryo–scanning electron microscopy and atomic force microscopy demonstrated that EPS form organic bridges between clay and quartz. The physicochemical properties of the EPS were characterized independently through wet chemical assays and Fourier transform infrared spectroscopy. The results indicated that several EPS components (e.g., proteins, polysaccharides) had a potential to complex with quartz and clay. Our findings provide novel insights in the importance of biofilms in the aggregation of clay and sand. Detrital coats from ancient estuarine sandstones show textural similarities to the experimental clay-EPS complexes and could be considered as biosignatures of biofilm development and EPS production in past environments.

Including indigenous knowledge in species distribution modeling for increased ecological insights.

Indigenous knowledge systems hold detailed information on current and past environments that can inform ecological understanding as well as contemporary environmental management. Despite its applicability, there are limited examples of indigenous knowledge being incorporated in species distribution models, which are widely used in the ecological sciences. In a collaborative manner, we designed a structured elicitation process and statistical framework to combine indigenous knowledge with survey data to model the distribution of a threatened and culturally significant species (greater bilby or mankarr [Macrotis lagotis]). We used Martu (Aboriginal people of the Australian western deserts) occurrence knowledge and presence data from track-based surveys to create predictive species distribution models with the Maxent program. Predictions of species distribution based on Martu knowledge were broader than those created with survey data. Together the Martu and survey models showed potential local declines, which were supported by Martu observation. Both data types were influenced by sampling bias that appeared to affect model predictions and performance. Martu provided additional information on habitat associations and locations of decline and descriptions of the ecosystem dynamics and disturbance regimes that influence occupancy. We concluded that intercultural approaches that draw on multiple sources of knowledge and information types may improve species distribution modeling and inform management of threatened or culturally significant species.

A late-Holocene record of coastal wetland development and fire regimes in tropical northern Australia

This study presents three records of environmental change during the late-Holocene from wetlands across Bentinck Island in the South Wellesley Islands, northern Australia. Radiometric dating provided ages for sediment cores with the longest chronology spanning the last 1250 cal. yr BP. Palynological results show the diverse mangrove community transitioned to woodland- and wetland-dominated vegetation over the last 850 years on the southeast coast. The key driver of this landscape change was likely late-Holocene sea level regression and coastal progradation in the Gulf of Carpentaria. This study found freshwater wetlands expanded across Bentick Island over the last 500 years, with sedges and rushes peaking in the last 350 years. Macroscopic and microscopic charcoal records, coupled with archaeological evidence, highlights the spatial and temporal variation in fire regimes across the island, reflecting the traditional fire management practices of the Kaiadilt people during the late-Holocene. This study finds a significant increase in charcoal accumulation in the 1900s when Kaiadilt fire practices were disrupted and the South Wellesley Islands were abandoned. The pollen record reflects little change in the vegetation despite the shifting fire regime, highlighting the importance of multi-proxy approaches to reconstructing past environments in tropical northern Australia where vegetation is adapted to fire.

A Study on Jia Jia Zhangke’s Introspection about Chinese Past Time and Environment Division ― Focusing on the Film Ash Is Purest White(江湖儿女)

A Study on Jia Jia Zhangke’s Introspection about Chinese Past Time and Environment Division ― Focusing on the Film Ash Is Purest White(江湖儿女)

Reflections on the Use of Ecological Attributes and Traits in Quaternary Botany

There has been an upsurge of interest and research activity in trait-based approaches in ecology, biogeography, and macroecology. I discuss if this upsurge has impacted Quaternary botany (the study of plant remains preserved in sediments). I show that ecological attributes (including traits) have played and continue to play an integral part in the interpretation of Quaternary botanical data in terms of reconstructing past environments and interpreting long-term changes in plant assemblages. This use started over 120 years ago and continues to the present. It is unclear if a ‘new’ Quaternary botany based on traits will develop because of the taxonomic limitations of much Quaternary botanical data.

Parallel Evolution of Tobramycin Resistance across Species and Environments.

Different species exposed to a common stress may adapt by mutations in shared pathways or in unique systems, depending on how past environments have molded their genomes. Understanding how diverse bacterial pathogens evolve in response to an antimicrobial treatment is a pressing example of this problem, where discovery of molecular parallelism could lead to clinically useful predictions. Evolution experiments with pathogens in environments containing antibiotics, combined with periodic whole-population genome sequencing, can be used to identify many contending routes to antimicrobial resistance. We separately propagated two clinically relevant Gram-negative pathogens, Pseudomonas aeruginosa and Acinetobacter baumannii, in increasing concentrations of tobramycin in two different environments each: planktonic and biofilm. Independently of the pathogen, the populations adapted to tobramycin selection by parallel evolution of mutations in fusA1, encoding elongation factor G, and ptsP, encoding phosphoenolpyruvate phosphotransferase. As neither gene is a direct target of this aminoglycoside, mutations to either are unexpected and underreported causes of resistance. Additionally, both species acquired antibiotic resistance-associated mutations that were more prevalent in the biofilm lifestyle than in the planktonic lifestyle; these mutations were in electron transport chain components in A. baumannii and lipopolysaccharide biosynthesis enzymes in P. aeruginosa populations. Using existing databases, we discovered site-specific parallelism of fusA1 mutations that extends across bacterial phyla and clinical isolates. This study suggests that strong selective pressures, such as antibiotic treatment, may result in high levels of predictability in molecular targets of evolution, despite differences between organisms' genetic backgrounds and environments.IMPORTANCE The rise of antimicrobial resistance is a leading medical threat, motivating efforts to forecast both its evolutionary dynamics and its genetic causes. Aminoglycosides are a major class of antibiotics that disrupt translation, but resistance may occur by a number of mechanisms. Here, we show the repeated evolution of resistance to the aminoglycoside tobramycin in both P. aeruginosa and A. baumannii via mutations in fusA1, encoding elongation factor G, and ptsP, encoding the nitrogen-specific phosphotransferase system. Laboratory evolution and whole-population genome sequencing were used to identify these targets, but mutations at identical amino acid positions were also found in published genomes of diverse bacterial species and clinical isolates. We also identified other resistance mechanisms associated with growth in biofilms that likely interfere with drug binding or uptake. Characterizing the evolution of multiple species in the presence of antibiotics can identify new, repeatable causes of resistance that may be predicted and counteracted by alternative treatment.

SouthwestAsiancerealcrops facilitated high-elevation agriculture in the central Tien Shan during the mid-third millennium BCE.

We report the earliest and the most abundant archaeobotanical assemblage of southwest Asian grain crops from Early Bronze Age Central Asia, recovered from the Chap II site in Kyrgyzstan. The archaeobotanical remains consist of thousands of cultivated grains dating to the mid-late third millennium BCE. The recovery of cereal chaff and weeds suggest local cultivation at 2000 m.a.s.l., as crops first spread to the mountains of Central Asia. The site’s inhabitants possibly cultivated two types of free-threshing wheats, glume wheats, and hulled and naked barleys. Highly compact caryopses of wheat and barley grains represent distinct morphotypes of cereals adapted to highland environments. While additional macrobotanical evidence is needed to confirm the presence of glume wheats at Chap II, the possible identification of glume wheats at Chap II may represent their most eastern distribution in Central Asia. Based on the presence of weed species, we argue that the past environment of Chap II was characterized by an open mountain landscape, where animal grazing likely took place, which may have been further modified by people irrigating agricultural fields. This research suggests that early farmers in the mountains of Central Asia cultivated compact morphotypes of southwest Asian crops during the initial eastward dispersal of agricultural technologies, which likely played a critical role in shaping montane adaptations and dynamic interaction networks between farming societies across highland and lowland cultivation zones.

Messinian vegetation and climate of the intermontane Florina-Ptolemais-Servia Basin, NW Greece inferred from palaeobotanical data: how well do plant fossils reflect past environments?

The late Miocene is marked by pronounced environmental changes and the appearance of strong temperature and precipitation seasonality. Although environmental heterogeneity is to be expected during this time, it is challenging to reconstruct palaeoenvironments using plant fossils. We investigated leaves and dispersed spores/pollen from 6.4 to 6 Ma strata in the intermontane Florina–Ptolemais–Servia Basin (FPS) of northwestern Greece. To assess how well plant fossils reflect the actual vegetation of the FPS, we assigned fossil taxa to biomes providing a measure for environmental heterogeneity. Additionally, the palynological assemblage was compared with pollen spectra from modern lake sediments to assess biases in spore/pollen representation in the pollen record. We found a close match of the Vegora assemblage with modern Fagus–Abies forests of Turkey. Using taxonomic affinities of leaf fossils, we further established close similarities of the Vegora assemblage with modern laurophyllous oak forests of Afghanistan. Finally, using information from sedimentary environment and taphonomy, we distinguished local and distantly growing vegetation types. We then subjected the plant assemblage of Vegora to different methods of climate reconstruction and discussed their potentials and limitations. Leaf and spore/pollen records allow accurate reconstructions of palaeoenvironments in the FPS, whereas extra-regional vegetation from coastal lowlands is probably not captured.