Southeastern South America Research Articles

Paralonchothrix gen. nov., the first record of Echimyini (Rodentia, Octodontoidea) in the late Miocene of Southern South America

ABSTRACTEchimyidae is the most widely diversified family among hystricognath rodents, both in the number of species and variety of lifestyles. In the Patagonian Subregion of southern South America, extinct echimyids related to living arboreal species (Echimyini) are recorded up to the middle Miocene, whereas all the known southern fossils since the late Miocene are linked to terrestrial and fossorial lineages currently inhabiting the Chacoan open biome in eastern South America. In this work, we describe a new genus of echimyid rodent, Paralonchothrix gen. nov., from the late Miocene of northwestern Argentina and western Brazil. Its single recognised species, Paralonchothrix ponderosus comb. nov., is represented by two hemimandibles. One of them comes from a level of Loma de Las Tapias Formation, underlying a tuff dated at 7.0 ± 0.9 Ma (Huayquerian age, late Miocene); the other specimen comes from the ‘Araucanense’ of Valle de Santa María (type locality, Huayquerian age, late Miocene). A phylogenetic analysis linked Paralonchothrix to Lonchothrix, both being the sister group to Mesomys. Thereby, for the first time, an echimyid linked to living Amazonian arboreal clades is recognised for the late Miocene of southern South America. Paralonchothrix gen. nov. thus represents an exceptional record that raises the need to review the postulated evolutionary pattern for echimyids recorded at high latitudes since the late Miocene. The new genus provides a minimum age (ca.7 Ma) in the fossil record for the divergence between Mesomys and Lonchothrix. The palaeoenvironmental conditions inferred for the late Miocene in western and northwestern Argentina suggest savanna-type environments, with areas with more closed woodlands in peri-Andean valleys. The record of Paralonchothrix gen. nov. supports the hypothesis that this area would have maintained connections with tropical biomes of northern South America during the late Miocene.

Co-occurrences of tropical trees in eastern South America: disentangling abiotic and biotic forces

Species co-occurrences in local communities can arise independent or dependent on species’ niches. However, the role of niche-dependent processes has not been thoroughly deciphered when generalized to biogeographical scales, probably due to combined shortcomings of data and methodology. Here, we explored the influence of environmental filtering and limiting similarity, as well as biogeographical processes that relate to the assembly of species’ communities and co-occurrences. We modelled jointly the occurrences and co-occurrences of 1016 tropical tree species with abundance data from inventories of 574 localities in eastern South America. We estimated species co-occurrences as raw and residual associations with models that excluded and included the environmental effects on the species’ co-occurrences, respectively. Raw associations indicate co-occurrence of species, whereas residual associations indicate co-occurrence of species after accounting for shared responses to environment. Generally, the influence of environmental filtering exceeded that of limiting similarity in shaping species’ co-occurrences. The number of raw associations was generally higher than that of the residual associations due to the shared responses of tree species to the environmental covariates. Contrary to what was expected from assuming limiting similarity, phylogenetic relatedness or functional similarity did not limit tree co-occurrences. The proportions of positive and negative residual associations varied greatly across the study area, and we found a significant tendency of some biogeographical regions having higher proportions of negative associations between them, suggesting that large-scale biogeographical processes limit the establishment of trees and consequently their co-occurrences.

Global BRAF testing practices in metastatic colorectal cancer (mCRC).

e15523 Background: The BRAF V600E mutation is a marker of poor prognosis in patients with mCRC. Targeted therapy, such as encorafenib + cetuximab, is approved in the US/Europe for the treatment of BRAF V600E-mutated mCRC and demonstrated improved survival vs historical standard of care (SOC). Determining BRAF mutation status in mCRC is recommended by NCCN and ESMO guidelines; although adherence to these guidelines may not be uniform. This report’s objective is to communicate global survey results of mCRC BRAF testing practices. Identifying regions where BRAF testing is not SOC may help identify where education efforts are needed to improve effective treatment decision making. Methods: Oncology treatment centers were identified from a registry and from public information. Centers were selected for research experience, historic data quality, and estimated numbers of mCRC patients. A BRAF testing practices survey using an online platform of verified centers was conducted from March to November 2020; 425 sites in 39 countries responded. Results: BRAF testing is performed as SOC most commonly in Northern and Western Europe (97%) and East Asia (95%). Conversely, BRAF testing as SOC is least common in Eastern Europe (47%) and South America (52%). Surveyed regions generally test patients when confirming advanced disease prior to first-line (1L) treatment (35% to 78%) or at initial histological diagnosis (9% to 41%). Most regions test tumor tissue; few test both tumor tissue and blood; and none conduct blood mutation testing only. Testing practices in the US by type of site (academic vs community) will be presented. Conclusions: BRAF testing has global variability, impacting treatment decisions. Increased awareness and routine testing may lead to informed decisions regarding targeted therapies, such as encorafenib + cetuximab (where approved), in patients with BRAF V600E-mutant mCRC.[Table: see text]

Gastric Cancer Associated Risk Factors and Prevalence in Pakistan

Gastric cancer (GC) is the most lethal disease of all cancer types. In the last three decades, it has become the most common reason for death among all cancer types. Gastric cancer is at the fourth number in all over the world and annually 8,00,000 deaths are reported. Female gastric cancer has been increased in the last 5 years. Unexpected diversity has been noted in GC spreaders in the whole world. Eastern Europe, China, and South America are the major regions of Gastric cancer prevalence. Its main sources are correlated with 2 agents, dietary intake and Helicobacter pylori infection. Although in south Asia occurrence of H. Pylori is high but less prevalence risk. The sole methods to minimize the prevalence of gastric cancer include elimination of Pylori, standard hygienic condition, proper diet, and improved living standards. One of the most common and complicated factors of gastric cancer is infection with Pylori. The main intention of this article is to elaborate the concerned review of GC and up-to-date information about its occurrence moreover its risk aspects in Pakistan.

Relationships between subseasonal‐to‐seasonal predictability and spatial scales in tropical rainfall

AbstractSubseasonal to seasonal (S2S) tropical rainfall predictability is assessed both from an analysis of the spatial scales of observed rainfall variability data, as well as from an S2S model reforecast skill. Observed spatial scales are quantified from gridded observed daily rainfall data, in terms of the size (area) of daily contiguous wet grid‐points (referred to as ‘wet patches’), as well as from the spatial autocorrelations of 7–91‐day running averages of rainfall. Model S2S reforecast skill is measured using the anomaly correlation coefficient between observed and simulated weekly and monthly rainfall from an 11‐member ensemble of European Centre for Medium‐Range Weather Forecasts (ECMWF) reforecasts (1998–2017). Both measures of S2S predictability are found to be systematically lower over land than sea, usually peaking at the start or end of the rainy season and decreasing during the core. Small spatial scales and low skill over equatorial/northern tropical Africa and western Amazonia coincide with small daily rainfall patch size and strong synoptic‐scale (≤7 days) variability there. Over most of South and SE Asia, daily wet patches are larger and strongly modulated by intraseasonal oscillations, boosting S2S rainfall predictability, while this is offset by large daily mean rainfall intensities that increase the noise. In consequence, S2S rainfall skill here generally remains low. Several land areas (as around Maritime Continent from the Philippines to Northern Australia, Eastern and Southern Africa, Eastern South America) exhibit larger spatial scales and skill, especially where the relative amplitude of SST‐forced interannual variations is strong. Most of the Maritime Continent illustrates such behaviour, but even here, the time‐averaged spatial scales and skill drop during the core of the rainy season.

Impacts of teleconnection patterns on South America climate.

Oceanic heat sources disturb the atmosphere, which, to come back to its initial state, disperses waves. These waves affect the climate in remote regions, characterizing the teleconnection patterns. In this study, we describe eight teleconnection patterns that affect South America climate: the El Niño-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO), the Tropical Atlantic Dipole (TAD), the South Atlantic Dipole (SAD), the Southern Annular Mode (SAM), the Madden-Julian Oscillation (MJO), and the Indian Ocean Dipole (IOD). Precipitation and winds at 850-hPa anomalies, considering these teleconnection patterns in ENSO neutral periods, are also presented. Overall, southeastern South America and the north sector of the North and Northeast regions of Brazil are the most affected areas by the teleconnection patterns. In general, there is a precipitation dipole pattern between these regions during each teleconnection pattern.

Evaluation of multiple reanalyses in reproducing the spatio‐temporal variability of temperature and precipitation indices over southern South America

AbstractSeveral temperature and precipitation indices, with special focus on extremes, were analysed in different sub‐regions of southern South America during 1979–2017 using multiple reanalyses, the CPC gridded data set and the most extended network of meteorological stations employed in regional climate studies up to date. Reanalyses generally well represented the spatial patterns of the indices, although they showed some differences in extreme indices over large portions of southern South America and tended to overestimate precipitation maximums, especially in southern Chile. Furthermore, ERA‐Interim presented clear difficulties in reproducing precipitation near the Andes Mountains, exhibiting the largest overestimations. This seemed to be improved in the new generation of ERA reanalyses (ERA5). When evaluating the long‐term changes, most of the data sets agreed in general warming conditions, stronger and more homogeneous for the maximum temperature. NCEP1 and NCEP2 reanalyses showed contrary temporal changes in almost all the temperature indices. Precipitation indices exhibited less consistent changes among reanalyses, although significant upward trends were detected for precipitation extremes in southeastern South America and downward trends were detected in southern Chile in the observational data sets. In addition, most of the data sets agreed in drier conditions in the arid diagonal region of Argentina as reflected by significant positive trends for dry spells and negative trends for the total annual precipitation. In terms of the inter‐annual correspondence, reanalyses usually presented good correlations to the stations reference in the regional averaged series, mainly for temperature indices and more variable for precipitation indices. Overall, no reanalysis was found to perform best. The use of reanalyses data to perform regional climate studies should consider the existent differences among them and with observational data. Moreover, using multiple sources of information is strongly recommended to account for observational uncertainty, especially in regions like southern South America, where data availability and its resolution are often limited.

Evaluation of multiple downscaling tools for simulating extreme precipitation events over Southeastern South America: a case study approach

A collection of 10 high-impact extreme precipitation events occurring in Southeastern South America during the warm season has been analyzed using statistical (ESD) and dynamical downscaling approaches. Regional Climate Models from the CORDEX database for the South American domain at two horizontal resolutions, 50 km and 25 km, short-term simulations at 20 km and at 4 km convective-permitting resolution and statistical downscaling techniques based on the analogue method and the generalized linear model approach were evaluated. The analysis includes observational datasets based on gridded data, station data and satellite products that allow assessing the observational uncertainty that characterizes extreme events in the region. It is found that the ability of the modelling strategies in capturing the main features of the extreme rainfall varies across the events. The higher the horizontal resolution of the models, the more intense and localized the core of the rainfall event, being the location of the exit region of the low-level jet and the low-level moisture flux convergence during the initial stages of the events the most relevant features that determine models’ ability of capturing the location and intensity of the core of the heavy rainfall. ESD models based on the generalized linear approach overestimate the spatial extension of the events and underestimate the intensity of the local maxima. Weather-like convective-permitting simulations depict an overall good performance in reproducing both the rainfall patterns and the triggering mechanisms of the extreme events as expected, given that these simulations are strongly controlled by the initial conditions.

Evidence for Middle Miocene origin and morphological evolutionary stasis in a Barbacenia Inselberg clade (Velloziaceae)

Atlantic Forest Inselbergs (AFI) and Campos Rupestres (CR) are mountains and highlands of eastern South America, relatively poorly studied and highly threatened, which display extraordinary levels of plant endemism and richness. In spite of their geographical and environmental differences, the origin of the flora of CR and AFI are likely linked to each other, because several plant clades are distributed across both ecosystems. In addition to these studies, little has been investigated about the historical biogeographical connections between AFI and CR and most evolutionary studies are restricted to CR. Barbacenia (Velloziaceae) is widely spread and nearly endemic to the AFI and CR outcrops and thus represent an ideal system to study the biogeographical connections between CR and AFI. Besides, given the remarkable diversity of Barbacenia in CR compared to AFI, it appears that different factors were important drivers in the diversification of Barbacenia lineages, likely leading to different patterns of morphological diversification. Here, we integrate phylogenetic, biogeographic and morphological approaches to: (i) address whether AFI species of Barbacenia are monophyletic and thus a single colonization of AFI can be inferred; (ii) understand the timing and geographical origin of CR and AFI clades; (iii) compare morphological diversity between Barbacenia from AFI and CR under the hypothesis that these two systems have experienced similar levels of morphological diversification during their evolutionary history. To this end, we presented a phylogeny inferred using plastid (atpB-rbcL, trnH-psbA and trnL-trnF) and nuclear (ITS) markers and a complete sampling of AFI Barbacenia, estimated divergence times, reconstructed the ancestral areas of Barbacenia clades and compared their morphological diversity based on a dataset of 16 characters. Our results provided evidence for a diversification of Barbacenia from the Middle Miocene to Pleistocene, as suggested in previous studies. We suggest that stepping-stone dispersal across mountaintops in interplay with paleovegetation dynamics during the global Miocene cooling and Pleistocene climatic oscillations may played an important role in the range expansion of modern AFI Barbacenia lineages. Finally, our results also showed a significant differences in morphological diversity between AFI and CR clades, suggesting a long-term morphological stasis in AFI species.

Extreme daily precipitation in southern South America: statistical characterization and circulation types using observational datasets and regional climate models

The main features of daily extreme precipitation and circulation types in southern South America (SSA) were evaluated and compared in both multiple observational datasets (rain gauges, CHIRPS, CPC and MSWEP) and simulations from four regional climate models (RCMs) driven by ERA-Interim during 1980–2010. The inter-comparison of extreme events, characterised in terms of their intensity, frequency and spatial coverage, varied across SSA showing large differences among observational datasets and RCMs and reflecting the current observational uncertainty when evaluating precipitation extremes at a daily scale. The spread between observational datasets was smaller than for the RCMs. Most of the RCMs successfully captured the spatial pattern of extreme precipitation across SSA, although RCA4 (REMO) usually underestimated (overestimated) precipitation intensities, particularly the maximum amounts in southeastern South America (SESA), where the extremes are remarkable. The synoptic circulation was described by a classification of circulation types (CTs) using Self-Organizing Maps (SOM). Specific CTs were found to significantly enhance the occurrence of extreme precipitation events in sectorized areas of SESA. The RCMs adequately reproduced the SOM node frequencies, although they tended to simplify the predominant CTs into a more reduced number of configurations. They appropriately represented the extreme precipitation frequencies conditioned by each CT, exhibiting some limitations in the location and intensity of the resulting precipitation systems. These sorts of evaluations contribute to a better understanding of the physical mechanisms responsible for extreme precipitation and of their future projections in a climate change scenario.

A Multi‐Proxy Approach to Unravel Late Pleistocene Sediment Flux and Bottom Water Conditions in the Western South Atlantic Ocean

AbstractMagnetic signals in deep‐sea sediments have the potential to unravel past continental environmental changes, via changes in primary terrigenous magnetic supply, but also record past marine environmental conditions, via in situ formation of secondary magnetic minerals, particularly when complemented by independent proxies. By combining environmagnetic, geochemical, and siliciclastic grain size data, we investigated marine sediment core GL‐1090 (24.92°S, 42.51°W, 2,225 m water depth) aiming to unravel changes in terrigenous sediment input and bottom water conditions during the last ∼184 ka at the western South Atlantic middepth. The Al/Si, Fe/κ and siliciclastic grain size data show that terrigenous sediments at this core location derived from the Plata River (southeastern South America). This material was transported northwards by the Brazilian Coastal Current and their delivery to our core site was modulated by sea‐level oscillations. Periods of low sea‐level were characterized by the input of coarser and more abundant terrigenous sediments. Environmagnetic parameters indicate significant downcore variations in the magnetic domain state, which we interpret as changes in the content of biogenic magnetite following glacial‐interglacial cycles. Coeval negative excursions in magnetic grain size and benthic δ13C suggests that concentrations of single domain magnetite (possibly magnetotactic bacterial magnetite) vary in response to middepth water ventilation. We suggest that reduced ventilation in the middepth western South Atlantic bottom waters during peak glaciations triggered a decrease in the production of biogenic magnetite. Peak glaciations were, in turn, linked with increases in the residence time of North Atlantic Deep Water (or its glacial counterpart).

Geoarchaeological signatures of anthropogenic soils in southeastern Uruguay: Approaches to formation processes and spatial–temporal variability

AbstractThis contribution focuses on the interpretation of earthen mound formation processes in the lowlands of the Pampa biome, southeastern Uruguay, through the integrated analysis of sedimentological and archaeological data. The three analyzed mounds from the La Tapera site have different heights and radiocarbon chronologies, indicating different construction periods across the last 4000 years. In addition, soils from surrounding plains were analyzed to provide a comparative basis for geoarchaeological characterization. From granulometric, compositional, and geochemical results, we identified different soil classes and several anthropogenic layers inside the earthen structures. Mound soils stood out from the rest due to higher levels of P, soil organic matter (SOM), and micro‐artifact content, leading to their classification as hortic Anthroportic Udorthent soils or hortic‐cultural cumulic archaeo‐anthrosols. Geoarchaeological differences between mounds are inferred as variations in the formation processes and/or construction technologies, possibly related to the functionality and height of the structures. Evidence from this contribution demonstrated the existence of ancient ways to produce nutrient‐rich long‐lasting anthropogenic soils that left persistent geoarchaeological signatures on the landscape. These findings highlight the need to broaden the discussion, culturally and geographically, about the genesis and development of management practices and associated indigenous knowledge to include the lowlands of southeastern South America.

Seasonal precipitation variability modes over South America associated to El Niño‐Southern Oscillation (ENSO) and non‐ENSO components during the 1951–2016 period

AbstractAnomalous seasonal patterns of precipitation variability over South America (SA) associated with El Niño‐Southern Oscillation (ENSO) and non‐ENSO (residual) conditions were assessed during 1951–2016. Patterns were obtained from empirical orthogonal functions analysis of total and residual precipitation seasonal anomalies. In austral spring and summer, precipitation variability is dominated by a dipolar anomaly mode with a centre extending from northwestern to northeastern SA and another in central‐eastern Brazil and part of southeastern SA (SESA) during spring, and a centre in northwestern SA and another extending from northeastern SA to central and eastern Brazil and central SESA, during summer. These modes are associated with ENSO to a greater extent during spring than summer. In summer, there is a strong association of the dipolar precipitation pattern with sea surface temperature (SST) anomalies on the east coast of Brazil, which indicates local influence. In austral fall, SST anomalies in the tropical South Atlantic relate to precipitation anomalies in northeast SA, and those in the tropical north Atlantic (TNA) to precipitation anomalies in northwestern SA, through the intertropical convergence zone anomalous position modulated by SST anomalies. In this same condition, the ENSO acts only to intensify or weaken the dominant precipitation pattern, depending on its phase, mainly over SESA. In contrast, the second variability mode in fall is characterized by positive SST anomalies in the Indian Ocean and equatorial and southern Atlantic Ocean and negative in the TNA. The importance of ENSO and the Indian Ocean in the characterization of the SST dipole in the tropical Atlantic explains the main changes in precipitation patterns over northeastern Brazil not been discussed in previous studies.

Impacts of Large-Scale Soil Moisture Anomalies on the Hydroclimate of Southeastern South America

AbstractThe La Plata basin (LPB), located in southeastern South America (SESA), is a region of significant socioeconomic importance, particularly for agriculture. This area of South America exhibits strong land–atmosphere coupling in the warm season. In this work, we evaluate the impact of large-scale soil moisture (SM) anomalies on regional-scale atmospheric conditions. Multivariate empirical orthogonal function (EOF) analysis is used to extract the dominant modes of joint variability of monthly averaged root-zone SM and 1-month-lagged precipitation from atmospheric reanalyses. We find that the dominant EOF pattern is consistent with a positive correlation between antecedent SM and precipitation, while the second dominant EOF pattern is consistent with a negative correlation between these variables. To evaluate causality, the effects of large-scale SM anomalies on atmospheric variables are examined using the Community Earth System Model (CESM). CESM simulations suggest that anomalously dry SM is initially collocated with decreased precipitation. Subsequent changes in the atmospheric circulation associated with a thermal low draw moisture into the region, eventually promoting increased precipitation. This study investigates the pathways through which SM anomalies modulate precipitation in this region. For this reason, this study has potential atmospheric prediction applications that could benefit the population and the socioeconomic well-being of this important region.

Observation‐Constrained Projection of Global Flood Magnitudes With Anthropogenic Warming

AbstractRiver flooding is among the costliest natural disasters with severe economic, societal, and environmental consequences. However, substantial uncertainties remain in global and regional projections of future flood conditions simulated by global climate models (GCMs) and/or global hydrological models (GHMs). Using physical models coupled with machine learning (ML), for the first time, we project changes in flood magnitudes of 2062 global river basins by constraining physical‐based streamflow simulations with observations under 1.5°C and 2°C warming scenarios identified for the Representative Concentration Pathway 8.5. We found that, during the validation period, the GHMs‐simulated flood magnitudes would improve with reduced uncertainty over the selected river basins after ML with a Long Short‐Term Memory network. Our estimation suggested that flood magnitudes would increase in many Northern Hemisphere mid‐ and high‐latitude rivers (e.g., Lena River, Amur River and Volga River) but decrease in some river basins in southern Finland and Eastern Europe in future periods (i.e., 1.5°C and 2°C warming levels). In 1.5°C and 2°C warmer worlds, the decreasing flood magnitudes in most South American rivers are associated with decreased soil moisture and increased evapotranspiration induced by warmer temperatures. Although the geographical pattern of changes in flood magnitudes for the +2°C experiment is close to that of the +1.5°C experiment, a 1.5°C warming target is more likely to reduce flood magnitudes of many river basins worldwide (e.g., in central and eastern Siberia, Alaska/Northwest Canada and South America).

Phylogenetic relationships, genetic diversity and biogeography of menhadens, genus Brevoortia (Clupeiformes, Clupeidae)

Brevoortia Gill 1861 is a genus of the Clupeidae (Teleostei) that includes six species of fishes commonly known as menhadens in eastern North America and “savelhas” or “saracas” in southeastern South America. Species of Brevoortia are important components of the marine food web of coastal ecosystems in the Atlantic and contribute significantly to fisheries. In this study, the first phylogenetic and biogeographic hypotheses including all species of Brevoortia are presented. A total of 113 specimens were analyzed using three molecular markers (two mitochondrial: COI and 16s; and one nuclear: RAG2). Maximum Parsimony, Maximum Likelihood and Bayesian Inference were employed to estimate phylogenetic relationships. A Bayesian multispecies coalescent approach was used to estimate a dated phylogeny, which supported biogeographic analyses of ancestral geographic ranges. Results corroborate previous hypotheses that the four North Atlantic species are grouped in two clades, one composed of B. tyrannus (Latrobe, 1802) and B. patronus Goode, 1878, and the second including B. smithi Hildebrand, 1941 and B. gunteri Hildebrand, 1948. The South Atlantic B. aurea (Spix and Agassiz, 1829) and B. pectinata (Jenyns, 1842) form a third clade, which is sister to the clade composed of B. smithi and B. gunteri. The monophyly and validity of the six nominal species of Brevoortia were not supported. Results also indicate that Brevoortia originated in the North Atlantic during the middle Miocene (about 15 Mya). A cooling event of the tropical Atlantic at around 10 Mya likely facilitated the range expansion of the genus to the South Atlantic, whereas a significant warming of the tropical Atlantic waters during the late Miocene at 6–7 Mya possibly promoted the isolation between the northern and southern counterparts of that ancestral lineage. The relevance of the Florida Peninsula in association with sea level fluctuations for the diversification within Brevoortia is also discussed.

Spatial proximity between polyploids across South American frog genera

AbstractAimPolyploids have been theorized to occur more frequently in environments that are subjected to severe conditions or sudden disruptions. Here we test the expectation that polyploid taxa occur more frequently in extreme or disrupted environments than their diploid counterparts, whether due to increased adaptive potential, environmental resilience or cross‐ploidy competition.LocationSouth America.TaxonAll frog genera in the area with both polyploid and diploid member species (Ceratophrys, Chiasmocleis, Odontophrynus, Phyllomedusa and Pleurodema).MethodsIn all, 13,556 occurrence records of 82 frog species were collected from the Global Biodiversity Information Facility. Species distribution models, range overlap estimates, statistical tests and principal component analyses were used to estimate and compare environments between diploid and polyploid species within and across genera using several categorical and quantitative variables taken from multiple publicly available sources.ResultsAlmost all polyploid occurrences are found within southeastern South America, largely to the exclusion of diploids. Polyploid species occur more closely with intergeneric polyploids than they do with congeneric diploids. Southeastern South America is more temperate, seasonal and less forested when compared to the tropical environments more commonly inhabited by diploids. The habitat ranges of polyploid species are subject to greater temperature fluctuations than diploid species. This region has also experienced major transformations in the modern era, owing to an agriculture boom over the last century. Polyploid occurrences are more likely to be found in areas with greater cropland usage, fertilizer application and pesticide application than diploids.Main ConclusionsAcross species, temperature seasonality was the only variable with strong statistical differences between diploids and polyploids. Greater annual fluctuations in temperature may lead to more established polyploid species due to reasons mentioned above; however, extreme temperature differences are also known to contribute to polyploid gamete formation, providing a possible non‐selective explanation. Polyploid occurrences are also more likely to be found in areas of high agricultural impact, providing support for the hypothesis that polyploids are more resilient to environmental disruptions than diploids.

The effect of global warming on the establishment of mangroves in coastal Louisiana during the Holocene

Winter temperature and sea-level position are critical factors affecting the global distribution of mangroves and saltmarshes. The replacement of saltmarshes by mangroves is expected due to global warming, reflecting the long-term natural trends in the Holocene and anthropogenic impacts since the 20th century. We documented the Holocene history of wetlands dynamics in the boreal limits of the American mangroves, located at Bay Champagne, Louisiana (USA), by integrating sedimentological, palynological, geochemical (δ13C and C\\N), X-ray fluorescence (XRF) data, and radiocarbon chronology from two sediment cores. The results indicated a freshwater lake environment with herbs and wetland ferns, as well as C3 terrestrial plants, between ~8100 and ~6500 cal yr BP. This environment shifted into a lagoon and saltmarshes having sedimentary organic matter sourced from marine algae between ~6500 and ~1500 cal yr BP. In the final stage, washover sediments were deposited in the lagoon during the last ~1500 cal yr BP. Despite the increased marine influence over the last ~6500 cal yr BP, mangrove pollen were not recorded between ~8100 and ~1500 cal yr BP, suggesting that mangroves were absent in the study area during that time interval. Historical evidence and a comparative analysis of our multi-proxy data with other mangrove studies from the Gulf of Mexico, Caribbean, and eastern South America revealed a gradual mangrove expansion from tropical to subtropical coasts of South and North America during the mid-late Holocene. The mangrove colonies at their current boreal (29° 09′ N) and austral (28° 29′ S) limits were established in the early and mid-20th century, respectively. This mangrove dynamics on a continental scale suggests that the poleward mangrove migration was likely caused by the warming climate during the Holocene. More importantly, the industrial-era warming has likely accelerated the mangrove expansion, but it was not the primary force that drove the mangrove migration into temperate zones.

Subseasonal Prediction Performance for Austral Summer South American Rainfall

AbstractSkillful and reliable predictions of week-to-week rainfall variations in South America, two to three weeks ahead, are essential to protect lives, livelihoods, and ecosystems. We evaluate forecast performance for weekly rainfall in extended austral summer (November–March) in four contemporary subseasonal systems, including a new Brazilian model, at 1–5-week leads for 1999–2010. We measure performance by the correlation coefficient (in time) between predicted and observed rainfall; we measure skill by the Brier skill score for rainfall terciles against a climatological reference forecast. We assess unconditional performance (i.e., regardless of initial condition) and conditional performance based on the initial phase of the Madden–Julian oscillation (MJO) and El Niño–Southern Oscillation (ENSO). All models display substantial mean rainfall biases, including dry biases in Amazonia and wet biases near the Andes, which are established by week 1 and vary little thereafter. Unconditional performance extends to week 2 in all regions except for Amazonia and the Andes, but to week 3 only over northern, northeastern, and southeastern South America. Skill for upper- and lower-tercile rainfall extends only to week 1. Conditional performance is not systematically or significantly higher than unconditional performance; ENSO and MJO events provide limited “windows of opportunity” for improved S2S predictions that are region and model dependent. Conditional performance may be degraded by errors in predicted ENSO and MJO teleconnections to regional rainfall, even at short lead times.

Last interglacial (MIS 5e) sea-level proxies in southeastern South America

Abstract. Coastal southeast South America is one of the classic locations where there are robust, spatially extensive records of past high sea level. Sea-level proxies interpreted as last interglacial (Marine Isotope Stage 5e, MIS 5e) exist along the length of the Uruguayan and Argentinian coast with exceptional preservation especially in Patagonia. Many coastal deposits are correlated to MIS 5e solely because they form the next-highest terrace level above the Holocene highstand; however, dating control exists for some landforms from amino acid racemization, U∕Th (on molluscs), electron spin resonance (ESR), optically stimulated luminescence (OSL), infrared stimulated luminescence (IRSL), and radiocarbon dating (which provides minimum ages). As part of the World Atlas of Last Interglacial Shorelines (WALIS) database, we have compiled a total of 60 MIS 5 proxies attributed, with various degrees of precision, to MIS 5e. Of these, 48 are sea-level indicators, 11 are marine-limiting indicators (sea level above the elevation of the indicator), and 1 is terrestrial limiting (sea level below the elevation of the indicator). Limitations on the precision and accuracy of chronological controls and elevation measurements mean that most of these indicators are considered to be low quality. The database is available at https://doi.org/10.5281/zenodo.3991596 (Gowan et al., 2020).