More than twenty years ago, a biological regulation of climate was proposed whereby emissions of dimethyl sulphide from oceanic phytoplankton resulted in the formation of aerosol particles that acted ...as cloud condensation nuclei in the marine boundary layer. In this hypothesis--referred to as CLAW--the increase in cloud condensation nuclei led to an increase in cloud albedo with the resulting changes in temperature and radiation initiating a climate feedback altering dimethyl sulphide emissions from phytoplankton. Over the past two decades, observations in the marine boundary layer, laboratory studies and modelling efforts have been conducted seeking evidence for the CLAW hypothesis. The results indicate that a dimethyl sulphide biological control over cloud condensation nuclei probably does not exist and that sources of these nuclei to the marine boundary layer and the response of clouds to changes in aerosol are much more complex than was recognized twenty years ago. These results indicate that it is time to retire the CLAW hypothesis.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Budding yeasts (subphylum Saccharomycotina) are found in every biome and are as genetically diverse as plants or animals. To understand budding yeast evolution, we analyzed the genomes of 332 yeast ...species, including 220 newly sequenced ones, which represent nearly one-third of all known budding yeast diversity. Here, we establish a robust genus-level phylogeny comprising 12 major clades, infer the timescale of diversification from the Devonian period to the present, quantify horizontal gene transfer (HGT), and reconstruct the evolution of 45 metabolic traits and the metabolic toolkit of the budding yeast common ancestor (BYCA). We infer that BYCA was metabolically complex and chronicle the tempo and mode of genomic and phenotypic evolution across the subphylum, which is characterized by very low HGT levels and widespread losses of traits and the genes that control them. More generally, our results argue that reductive evolution is a major mode of evolutionary diversification.
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•332 genomes, including 220 newly sequenced, covering ∼1/3 of known budding yeasts•Genome-scale inference of robust phylogeny and time tree of budding yeast subphylum•Reconstruction of 45 metabolic traits infers complex budding yeast common ancestor•Reductive evolution of traits and genes is a major mode of evolutionary diversification
An integrated phylogeny of over 300 budding yeast species encompasses the natural diversity and history of diversification of Saccharomycotina with insights into a metabolically complex common ancestor and common reductive evolution leading to metabolic specialization.
•Thermal limits to survival, performance, and moulting of American lobster larvae were reviewed.•Larvae are stressed or die at temperatures ≥24–36°C, which will be more frequent in the ...future.•Moulting, growth, hatching, and settlement of larvae may be reduced or stop above 20–24°C.•Previous studies’ results need to be confirmed through more rigorous, new studies.•Stressful temperatures to larvae must be known to predict impacts of climate change on lobsters.
Warming generally improves performance of life processes such as moulting and growth in ectotherms, but excessive warming can reduce performance and cause death, which in turn affects their demography. Previous studies of American lobster, Homarus americanus, have considered warming impacts on benthic adults, but little attention has been paid to performance of planktonic larvae at extremely high temperatures. Water column temperatures are expected to increase faster than bottom temperatures, so warming may compromise physiological performance of larvae sooner than that of adults. It is thus important to identify stressful and lethal temperatures for lobster larvae, and include these when estimating climate change impacts. Previous studies that observed survival, development, moulting, growth, and physiological performance of lobster larvae at extreme temperatures were reviewed. Mortality following short-term exposure to 28–36°C from minutes to hours in duration has been reported, but more ecologically-relevant longer-term high-temperature exposures lasting days or weeks have rarely been tested for larvae of this species. Sub-lethal indicators of stress such as irregular heartbeat were reported in short- and long-term exposures between 20 and 26°C, suggesting that perhaps extended exposure to these temperatures could be lethal. Over the next 10–50 years, larvae may experience temperatures up to 30°C, which could negatively impact lobster populations if these temperatures are indeed stressful or lethal to them. Knowledge gaps identified highlight the need for further research into tolerance of lobster larvae to high temperatures.
Hybridization between species is widespread across the tree of life. As a result, many species, including our own, harbor regions of their genome derived from hybridization. Despite the recognition ...that this process is widespread, we understand little about how the genome stabilizes following hybridization, and whether the mechanisms driving this stabilization tend to be shared across species. Here, we dissect the drivers of variation in local ancestry across the genome in replicated hybridization events between two species pairs of swordtail fish: Xiphophorus birchmanni × X. cortezi and X. birchmanni × X. malinche. We find unexpectedly high levels of repeatability in local ancestry across the two types of hybrid populations. This repeatability is attributable in part to the fact that the recombination landscape and locations of functionally important elements play a major role in driving variation in local ancestry in both types of hybrid populations. Beyond these broad scale patterns, we identify dozens of regions of the genome where minor parent ancestry is unusually low or high across species pairs. Analysis of these regions points to shared sites under selection across species pairs, and in some cases, shared mechanisms of selection. We show that one such region is a previously unknown hybrid incompatibility that is shared across X. birchmanni × X. cortezi and X. birchmanni × X. malinche hybrid populations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The authors examine the chemistry and related properties of freshly emitted sea spray aerosol. Topics discussed include the seawater organic carbon pool.
Frequent exposure to green space has been linked to positive health and well-being in varying populations. Yet, there is still limited research exploring the restorative benefits associated with ...differing types of green space use among students living in the university setting. To address this gap, we explored green space use amongst a population of undergraduate students (n = 207) attending a university with abundant opportunities to access the restorative properties of nature. The purpose of this study was to examine the type and frequency of green space interactions that are most strongly associated with indicators of health and well-being, and investigate student characteristics associated with frequent use of green space. Results revealed that students who frequently engage with green spaces in active ways report higher quality of life, better overall mood, and lower perceived stress. Passive green space interactions were not strongly associated with indicators of health and well-being. Having had daily interactions with green space in childhood was associated with frequent green space use as a university student, and identified barriers to green space use included "not enough time," and "not aware of opportunities" These results could assist in the tailoring of "green exercise" interventions conducted in the university setting.
Transformations that selectively functionalize aliphatic C–H bonds hold significant promise to streamline complex molecule synthesis. Despite the potential for site-selective C–H functionalization, ...few intermolecular processes of preparative value exist. Herein, we report an approach to unactivated, aliphatic C–H bromination using readily available N-bromoamide reagents and visible light. These halogenations proceed in useful chemical yields, with substrate as the limiting reagent. The site selectivities of these radical-mediated C–H functionalizations are comparable (or superior) to the most selective intermolecular C–H functionalizations known. With the broad utility of alkyl bromides as synthetic intermediates, this convenient approach will find general use in chemical synthesis.
Atmospheric black carbon (BC) warms Earth's climate, and its reduction has been targeted for near-term climate change mitigation. Models that include forcing by BC assume internal mixing with non-BC ...aerosol components that enhance BC absorption, often by a factor of ∼2; such model estimates have yet to be clearly validated through atmospheric observations. Here, direct in situ measurements of BC absorption enhancements (E abs ) and mixing state are reported for two California regions. The observed E abs is small—6% on average at 532 nm—and increases weakly with photochemical aging. The E abs is less than predicted from observationally constrained theoretical calculations, suggesting that many climate models may overestimate warming by BC. These ambient observations stand in contrast to laboratory measurements that show substantial E abs for BC are possible.
Investigating how environmental features shape the genetic structure of populations is crucial for understanding how they are potentially adapted to their habitats, as well as for sound management. ...In this study, we assessed the relative importance of spatial distribution, ocean currents and sea surface temperature (SST) on patterns of putatively neutral and adaptive genetic variation among American lobster from 19 locations using population differentiation (PD) approaches combined with environmental association (EA) analyses. First, PD approaches (using bayescan, arlequin and outflank) found 28 outlier SNPs putatively under divergent selection and 9770 neutral SNPs in common. Redundancy analysis revealed that spatial distribution, ocean current‐mediated larval connectivity and SST explained 31.7% of the neutral genetic differentiation, with ocean currents driving the majority of this relationship (21.0%). After removing the influence of spatial distribution, no SST were significant for putatively neutral genetic variation whereas minimum annual SST still had a significant impact and explained 8.1% of the putatively adaptive genetic variation. Second, EA analyses (using Pearson correlation tests, bayescenv and lfmm) jointly identified seven SNPs as candidates for thermal adaptation. Covariation at these SNPs was assessed with a spatial multivariate analysis that highlighted a significant temperature association, after accounting for the influence of spatial distribution. Among the 505 candidate SNPs detected by at least one of the three approaches, we discovered three polymorphisms located in genes previously shown to play a role in thermal adaptation. Our results have implications for the management of the American lobster and provide a foundation on which to predict how this species will cope with climate change.
Approximately 3 billion people, most of whom live in Asia, Africa, and the Americas, rely on solid fuels (i.e. wood, crop wastes, dung, charcoal) and kerosene for their cooking needs. Exposure to ...household air pollution from burning these fuels is estimated to account for approximately 3 million premature deaths a year. Cleaner fuels – such as liquefied petroleum gas, biogas, electricity, and certain compressed biomass fuels – have the potential to alleviate much of this significant health burden. A wide variety of clean cooking intervention programs are being implemented around the world, but very few of these efforts have been analyzed to enable global learning. The Clean Cooking Implementation Science Network (ISN), supported by the U.S. National Institutes of Health (NIH) and partners, identified the need to augment the publicly available literature concerning what has worked well and in what context. The ISN has supported the development of a systematic set of case studies, contained in this Special Issue, examining clean cooking program rollouts in a variety of low- and middle-income settings around the world. We used the RE-AIM (reach, effectiveness, adaptation, implementation, maintenance) framework to coordinate and evaluate the case studies. This paper describes the clean cooking case studies project, introduces the individual studies contained herein, and proposes a general conceptual model to support future planning and evaluation of household energy programs.
•Clean fuels for cooking, e.g. LPG, biogas, electricity, and ethanol/methanol, could provide public health benefits.•Diverse clean cooking initiatives are being implemented around the world, but very few of these efforts have been analyzed.•The Clean Cooking Implementation Science Network solicited proposals for case studies of clean cooking scale-up efforts.•Eleven case studies were developed, spanning multiple fuel types and locations across South America, Africa, and Asia.•Results suggest that programs require additional attention to monitoring and sustainability to maximize benefits.
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