Germination and seedling growth of the Chilean native grass Polypogon australis in soil polluted with diesel oil.

The purpose of this study was to evaluate the ability of Polypogon australis, a Chilean native grass that colonizes copper polluted sites, to germinate and grow in soil contaminated with diesel oil. The effect of increasing proportions of diesel in soil (0.5%, 1%, 2%, and 5%) on the cumulative germination and growth of plants was measured. The relative seed germination (RSG), relative root growth (RRG), germination index (GI), and the effective concentration (EC50) were calculated. The cumulative germination in soil polluted with 0%, 0.5%, 1%, and 2% of diesel oil in soil was 93.3%, 85.5%, 99%, and 78.5%, respectively, showing no significant differences between the treatments (p > 0.05). A proportion of 5% of diesel in the soil reduced the germination of P. australis by 50%, compared to the control. The growth of leaves and roots of the plants germinated in 5% of diesel was reduced by 30% compared to the control, with a 34% survival rate observed on day 40. The calculated EC50 of diesel for P. australis was 4.5%. P. australis germinated and grew on all diesel concentration used in the experiments. The species was classified as a tolerant to diesel oil.

Understanding how environmental degradation, microclimate, and management shape honey production across different spatial scales.

Although the abundance, survival, and pollination performance of honeybees are sensitive to changes in habitat and climate conditions, the processes by which these effects are transmitted to honey production and interact with beekeeping management are not completely understood. Climate change, habitat degradation, and beekeeping management affect honey yields, and may also interact among themselves resulting in indirect effects across spatial scales. We conducted a 2-year, multi-scale study on Chiloe Island (northern Patagonia), where we evaluated the most relevant environmental and management drivers of honey produced by stationary beekeepers. We found that the effects of microclimate, habitat, and management variables changed with the spatial scale. Among the environmental variables, minimum temperature, and cover of the invasive shrub, gorse (Ulex europaeus) had the strongest detrimental impacts on honey production at spatial scales finer than 4 km. Specialized beekeepers who adopted conventional beekeeping and had more mother colonies were more productive. Mean and minimum temperatures interacted with the percentage of mother colonies, urban cover, and beekeeping income. The gorse cover increased by the combination of high temperatures and the expansion of urban lands, while landscape attributes, such as Eucalyptus plantation cover, influenced beekeeping management. Results suggest that higher temperatures change the available forage or cause thermal stress to honeybees, while invasive shrubs are indicators of degraded habitats. Climate change and habitat degradation are two interrelated environmental phenomena whose effects on beekeeping can be mitigated through adaptive management and habitat restoration.

Covariation of taxonomic and functional facets of ß-diversity in Chilean freshwater fish assemblages: Implications for current and future processes of biotic homogenization.

The biodiversity of assemblages that experience the introduction and extinction of species may lead to responses in two important facets: The taxonomic and functional diversity. The way in which these facets are associated may reveal important implications and consequences for the conservation of those assemblages. Considering the critical situation of freshwater fishes in continental Chile (30° - 56° S), we analyzed how the taxonomic (TDß) and functional (FDß) facets of ß-diversity, and their components of turnover and nestedness, are associated. We evaluated changes in ß-diversity (ΔTDß and ΔFDß), turnover (ΔTDtur and ΔFDtur), and nestedness (ΔTDnes and ΔFDnes) in 20 fish assemblages from their historical (pre-European) to current composition. We also simulated future trends of these changes, assuming that native species with conservation issues would become extinct. Our results show that the fish assemblages studied are in a process of loss of ß-diversity, both in taxonomic and functional facets (ΔTDß = -3.9%; ΔFDß = -30.4%); also, that these facets are positively correlated in the assemblages studied (r = 0.617; P < 0.05). Both components showed by loss in nestedness (ΔTDnes = -36.9%; ΔFDnes = -60.9%) but gain in turnover (ΔTDtur = 9.2%; ΔFDtur = 12.3%). The functional ß-diversity decreased more than the taxonomic (ΔFDß > ΔTDß), which was caused chiefly by six exotic species of Salmonidae, whose geographical spread was wider and that at the same time shared several morpho-functional traits. Our forecasts, assuming an intensification in the extinction of Endangered and Vulnerable native species, indicate that the process of homogenization will continue, though at a lower rate. Our study shows that the freshwater ichthyofauna of continental Chile is undergoing biotic homogenization, and that this process involves the facets of taxonomic and functional ß-diversity, which are show high correlation between historical and current compositions. Both facets show that process is influenced by nestedness, and while turnover contributes to differentiation (both taxonomic and functional), its importance is overshadowed by nestedness.

Comparison of the First and Second Wave of Infections by SARS-CoV-2: A Retrospective and Longitudinal Study From a Primary Health Care Center in Santiago of Chile.

The current COVID-19 pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Many countries have reported the experience of at least two contagion waves, describing associated mortality rates and population behavior. The analysis of the effect of this pandemic in different localities can provide valuable information on the key factors to consider in the face of future massive infectious diseases. This work describes the first retrospective and comparative study about behavior during the first and second waves of the COVID-19 pandemic in Chile from a primary Healthcare Center. From 19,313 real-time quantitative PCR (RT-qPCR) tests assessed, the selected 1,694 positive diagnostics showed a decrease in mortality rate in the second wave (0.6%) compared with the first (4.6%). In addition, we observed that infections in the second wave were mainly in young patients with reduced comorbidities. The population with a complete vaccination schedule shows a decrease in the duration of symptoms related to the disease, and patients with more comorbidities tend to develop severe illness. This report provides evidence to partially understand the behavior and critical factors in the severity of the COVID-19 pandemic in the population of Santiago of Chile.

Partitioning ß-diversity reveals that invasions and extinctions promote the biotic homogenization of Chilean freshwater fish fauna.

AIM: Exotic species' introductions together with extinction of native species represent the main mechanisms driving biotic homogenization of freshwater fish assemblages around the world. While generally ichtyofaunistic realms transit towards biotic homogenization, for conservation purposes it is essential to understand what specific mechanisms are promoting it on particular areas or regions. Here, we report the occurrence of biotic homogenization in 29 Chilean watersheds, analyzing its ß-diversity (including turnover and nestedness) and predicting future trends. LOCATION: Continental Chile (18o-56o S). METHODS: We determined fish composition per basin for historical and current assemblages; extant native, exotic, and extinct species were recorded as 1 (presence) or 0 (absence) in two matrices basins × species. For each matrix, we calculated the turnover (ßsim), nestedness (ßnes), and ß-diversity (ßsor); then, we obtained Δßsim, Δßnes, and Δßsor, as the arithmetical difference between basin pairs over time. In addition, we search for explanatory variables correlating Δßsim, Δßnes, and Δßsor with geographical and land use variables. Finally, simulating events of species introduction (i.e., invasion) and extinction, we generated 15 hypothetical assemblages, looking to establish future trends towards biotic change in Chilean basins. RESULTS: Species turnover and ß-diversity significantly decreased from historical to current assemblages (Δßsim = -0.084; Δßsor = -0.061, respectively), while the species nestedness did not show significant changes (Δßnes = 0.08). Biotic changes have been driven mainly by the introduction of 28 exotic species, with a minor role of extinctions (one species) and translocations (0 species) of native species. Changes in ß-diversity were negatively correlated with area, elevation, and geographical distance between basins but not with land-use nor human population. Finally, the analysis of 15 future assemblages predicts a significant decrease of ß-diversity and turnover, and an increase for species nestedness, this time promoted by an increase in the extinction of native species. MAIN CONCLUSION: Chilean basins show a significant decrease of the distributional ß-diversity and species turnover of the freshwater fish fauna, evidencing a trend towards biotic homogenization. This trend is shared with other Neotropical basins; however, specific mechanisms driving it show different magnitude. Changes in the ß-diversity components do not show correlation with variables associated to land use, thus suggesting that casual introductions of freshwater fishes in Chile follow an opportunistic mode related to commercial use. According to future scenarios simulated, biotic homogenization should increase further, mainly as consequence of increased native extinctions.

Recent Progress in Nanomaterials for Modern Concrete Infrastructure: Advantages and Challenges.

Modern concrete infrastructure requires structural components with higher mechanical strength and greater durability. A solution is the addition of nanomaterials to cement-based materials, which can enhance their mechanical properties. Some such nanomaterials include nano-silica (nano-SiO2), nano-alumina (nano-Al2O3), nano-ferric oxide (nano-Fe2O3), nano-titanium oxide (nano-TiO2), carbon nanotubes (CNTs), graphene and graphene oxide. These nanomaterials can be added to cement with other reinforcement materials such as steel fibers, glass, rice hull powder and fly ash. Optimal dosages of these materials can improve the compressive, tensile and flexural strength of cement-based materials, as well as their water absorption and workability. The use of these nanomaterials can enhance the performance and life cycle of concrete infrastructures. This review presents recent researches about the main effects on performance of cement-based composites caused by the incorporation of nanomaterials. The nanomaterials could decrease the cement porosity, generating a denser interfacial transition zone. In addition, nanomaterials reinforced cement can allow the construction of high-strength concrete structures with greater durability, which will decrease the maintenance requirements or early replacement. Also, the incorporation of nano-TiO2 and CNTs in cementitious matrices can provide concrete structures with self-cleaning and self-sensing abilities. These advantages could help in the photocatalytic decomposition of pollutants and structural health monitoring of the concrete structures. The nanomaterials have a great potential for applications in smart infrastructure based on high-strength concrete structures.

Invasions but not extinctions change phylogenetic diversity of angiosperm assemblage on southeastern Pacific Oceanic islands.

We assessed changes in phylogenetic diversity of angiosperm flora on six oceanic islands located in the southeastern Pacific Ocean, by comparing flora from two periods: the pre-European colonization of islands and current times. We hypothesize that, in the time between these periods, extinction of local plant species and addition of exotic plants modified phylogenetic-α-diversity at different levels (deeper and terminal phylogeny) and increased phylo-ß-diversity among islands. Based on floristic studies, we assembled a phylogenetic tree from occurrence data that includes 921 species, of which 165 and 756 were native or exotic in origin, respectively. Then, we studied change in the phylo-α-diversity and phylo-ß-diversity (1 -Phylosor) by comparing pre-European and current times. Despite extinction of 18 native angiosperm species, an increase in species richness and phylo-α-diversity was observed for all islands studied, attributed to introduction of exotic plants (between 6 to 477 species per island). We did not observe significant variation of mean phylogenetic distance (MPD), a measure of the 'deeper' phylogenetic diversity of assemblages (e.g., orders, families), suggesting that neither extinctions nor introductions altered phylogenetic structure of the angiosperms of these islands. In regard to phylo-ß-diversity, we detected temporal turnover (variation in phylogenetic composition) between periods to flora (0.38 ± 0.11). However, when analyses were performed only considering native plants, we did not observe significant temporal turnover between periods (0.07 ± 0.06). These results indicate that introduction of exotic angiosperms has contributed more notably than extinctions to the configuration of plant assemblages and phylogenetic diversity on the studied islands. Because phylogenetic diversity is closely related to functional diversity (species trait variations and roles performed by organisms), our results suggests that the introduction of exotic plants to these islands could have detrimental impacts for ecosystem functions and ecosystem services that islands provide (e.g. productivity).

Evaluating Darwin's naturalization hypothesis in experimental plant assemblages: phylogenetic relationships do not determine colonization success.

Darwin's naturalization hypothesis (DNH) proposes that colonization is less likely when the colonizing species is related to members of the invaded community, because evolutionary closeness intensifies competition among species that share similar resources. Studies that have evaluated DNH from correlational evidence have yielded controversial results with respect to its occurrence and generality. In the present study we carried out a set of manipulative experiments in which we controlled the phylogenetic relatedness of one colonizing species (Lactuca sativa) with five assemblages of plants (the recipient communities), and evaluated the colonizing success using five indicators (germination, growth, flowering, survival, and recruitment). The evolutionary relatedness was calculated as the mean phylogenetic distance between Lactuca and the members of each assemblage (MPD) and by the mean phylogenetic distance to the nearest neighbor (MNND). The results showed that the colonization success of Lactuca was not affected by MPD or MNND values, findings that do not support DNH. These results disagree with experimental studies made with communities of microorganisms, which show an inverse relation between colonization success and phylogenetic distances. We suggest that these discrepancies may be due to the high phylogenetic distance used, since in our experiments the colonizing species (Lactuca) was a distant relative of the assemblage members, while in the other studies the colonizing taxa have been related at the congeneric and conspecific levels. We suggest that under field conditions the phylogenetic distance is a weak predictor of competition, and it has a limited role in determining colonization success, contrary to prediction of the DNH. More experimental studies are needed to establish the importance of phylogenetic distance between colonizing species and invaded community on colonization success.

Nutrients dynamics in the main river basins of the centre-southern region of Chile.

Chilean basins have long been exposed to nutrient discharges from human activities and land use changes. A historical seasonal NO(3)(-)-N and PO(4)(3-)-P database of the last 23 years of the main nine rivers of central-southern region of Chile was analysed. Generalized additive models indicated that annual trends in NO(3)(-)-N and PO(4)(3-)-P are nonlinear. River basins such as Bío-Bío, Bueno, Imperial, Maule, Rapel and Valdivia showed a clear increase in NO(3)(-)-N, while PO(4)(3-)-P increased only in the Rapel and Maule basins. Although no seasonal difference in NO(3)(-)-N and PO(4)(3-)-P was found in the analysed basins, there was a negative relation between these nutrients and water flow. Sampling stations with high NO(3)(-)-N concentration were found mostly in sub-basins located in the "central valley" of central Chile, while several PO(4)(3-)-P "over-concentrated" sampling stations were located mostly upstream. If NO(3)(-)-N emissions into Chilean river basins continue at current rates it is probable that the concentration of this nutrient will tend to match that of the most "polluted" rivers around the world.