Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"
Recent publications
Peat bogs have an important role in the carbon cycle, as they may be sinks or sources of carbon dioxide and methane, depending on the environmental conditions. These wetlands represent large reservoirs of freshwater capable of mitigating drought-flood events, with important implications for water quality and hydrological balance. The key nature contributions to people provided by these ecosystems are tightly related with the diversity of microbial communities inhabiting them. Peat bogs from Tierra del Fuego Island usually host several water bodies embedded within a waterlogged Sphagnum matrix. These aquatic habitats can be considered as extreme environments due to their low pH values and dystrophic conditions and show a uniquely adapted biota. In this chapter, we unravel the diversity of the aquatic algae, ciliate and microinvertebrate communities from two peat bogs from Tierra del Fuego at different scales. For the different communities analysed, we identified distinct diversity patterns relating to local environmental conditions, as well as taxa of high value as indicators of the possible impact on peat bog diversity exerted by anthropogenic activities in a global change context.KeywordsTierra del Fuego Peat bogs Anthropogenic impact Global change Aquatic communities
Species are the fundamental category and the key to formulate conservation efforts. DNA and ecological niche modeling have become valuable tools for species delimitation. Wolf spiders include few web-living species, such as Aglaoctenus lagotis (Holmberg, 1876), a priority species for conservation in Uruguay. Behavioral and body coloration patterns of this species have allowed us to distinguish two groups (forms I and II). Here, we combine information from gene trees and multispecies coalescent analyses on mitochondrial (cox1, 12S, 16S+L1+nad1) and nuclear (intron tif5A) DNA sequences, as well as from ecological niches comparisons, in order to clarify their taxonomic identity. We worked with localities in Uruguay and Argentina, including sympatric and allopatric areas. Gene trees were inferred with Maximum Likelihood, Bayesian, and statistical parsimony analyses. Molecular species delimitation analyses were conducted, and the species tree and divergence times were co-estimated. Characterization and comparison of the climatic requirements of both forms throughout annual and sexual periods were analyzed. Species delimitation and species tree analyses recovered three main lineages (Form I, Form IIa, and Form IIb). Form I is restricted to Uruguay and is closely related and sympatric with Form IIa. Form IIb is located in Argentina and in the Uruguayan west coast, generating a sympatric area of the three forms. Regarding to the sexual climatic niche, the three main lineages differ and do not overlap. Our results support the existence of more than one lineage within what is nowadays Aglaoctenus lagotis. Possible evolving processes explaining this scenario and the conservation consequences are discussed
Among terrestrial vertebrates, only crown birds (Neornithes) rival mammals in terms of relative brain size and behavioural complexity. Relatedly, the anatomy of the avian central nervous system and associated sensory structures, such as the vestibular system of the inner ear, are highly modified with respect to those of other extant reptile lineages. However, a dearth of three-dimensional Mesozoic fossils has limited our knowledge of the origins of the distinctive endocranial structures of crown birds. Traits such as an expanded, flexed brain, a ventral connection between the brain and spinal column, and a modified vestibular system have been regarded as exclusive to Neornithes. Here, we demonstrate all of these 'advanced' traits in an undistorted braincase from an Upper Cretaceous enantiornithine bonebed in southeastern Brazil. Our discovery suggests that these crown bird-like endocranial traits may have originated prior to the split between Enantior-nithes and the more crownward portion of avian phylogeny over 140 Ma, while coexisting with a remarkably plesiomorphic cranial base and posterior palate region. Altogether, our results support the interpretation that the distinctive endocranial morphologies of crown birds and their Mesozoic relatives are affected by complex trade-offs between spatial constraints during development.
Recluse or violin spiders in the genus Loxosceles (Scytodoidea: Sicariidae) are a diverse group (~140 extant species) including medically important species and distributed mainly in the Americas, Africa, and the Mediterranean region. In addition, this genus includes three fossil species from Miocene Dominican amber. Here we revise the taxonomy of these fossil species by examining, imaging and re-describing their type specimens. We find that L. defecta Wunderlich, 1988 and L. deformis Wunderlich, 1988 are bona fide members of the genus and report additional characters overlooked in their original descriptions. We further study the ho-lotype of L. aculicaput Wunderlich, 2004 using synchrotron radiation micro-computed tomography to reveal previously unknown morphological details hidden by fissures in the amber. We found several characters inconsistent with Loxosceles but consistent with Drymusa (false violin spiders; Scytodoidea: Drymusidae), such as three claws, well-developed podotarsite, and a broad colulus. This suggests the species is misplaced in Loxosceles. To test this hypothesis, we estimated a total-evidence phylogeny of the superfamily Scytodoidea including extant and fossil taxa, morphological data, traditional molecular markers, and sequences of ultra-conserved elements. The results show unambiguously that L. aculicaput belongs to Drymusa and is a close relative of extant species of the genus inhabiting the Greater Antilles. Therefore, we here transfer this species to Drymusa, establishing a new combination and new family assignment. Drymusa aculicaput comb. nov. represents the first known fossil Drymusidae and shows that crown members of this genus already existed in the Miocene.
Skorpiovenator bustingorryi is a derived abelisaurid theropod represented by a fairly complete skeleton from the Late Cretaceous sedimentary beds of north-western Patagonia. Although some features were described in the original paper, mainly related to the skull, the appendicular anatomy remains undescribed. The aim of the present contribution is to provide a detailed description and analysis of the available appendicular bones, including comparisons with other ceratosaurian theropods close to Skorpiovenator. In this way, new autapomorphies emerged to further distinguish Skorpiovenator from its relatives. Furthermore, a comprehensive phylogenetic analysis was performed and several characteristics of the hind limb, in particular some of the autopodium, resulted in the identification of new apomorphic traits for Ceratosauria and Abelisauridae. These features might prove to be useful for future phylogenetic analyses and may help to resolve the still confusing and debated internal relationships of abelisaurid theropods.
Understanding the drivers of morphological convergence requires investigation into its relationship with behavior and niche-space, and such investigations in turn provide insights into evolutionary dynamics, functional morphology, and life history. Mygalomorph spiders (trapdoor spiders and their kin) have long been associated with high levels of homoplasy, and many convergent features can be intuitively associated with different behavioral niches. Using genus-level phylogenies based on recent genomic studies and a newly assembled matrix of discrete behavioral and somatic morphological characters, we reconstruct the evolution of burrowing behavior in the Mygalomorphae, compare the influence of behavior and evolutionary history on somatic morphology, and test hypotheses of correlated evolution between specific morphological features and behavior. Our results reveal the simplicity of the mygalomorph adaptive landscape, with opportunistic, web-building taxa at one end, and burrowing/nesting taxa with structurally-modified burrow entrances (e.g., a trapdoor) at the other. Shifts in behavioral niche, in both directions, are common across the evolutionary history of the Mygalomorphae, and several major clades include taxa inhabiting both behavioral extremes. Somatic morphology is heavily influenced by behavior, with taxa inhabiting the same behavioral niche often more similar morphologically than more closely-related but behaviorally-divergent taxa, and we were able to identify a suite of 11 somatic features that show significant correlation with particular behaviors. We discuss these findings in light of the function of particular morphological features, niche dynamics within the Mygalomorphae, and constraints on the mygalomorph adaptive landscape relative to other spiders.
An overview of the knowledge of the invasive feshwater golden mussel (Limnoperna fortunei) is presented, with particular emphasis on the voids of our current understanding of its ecology and its effects on the systems invaded. L. fortunei started spreading northwards in China after 1960, and ~ 1990 it invaded Japan and South America. These invasions fostered a strong increase in the interest in the mussel. However, coverage of its biology, ecology, and impacts has been very uneven. Geographic distribution and spread, seasonal dynamics and methods for controlling its fouling in industrial plants and other human-made facilities have received most of the attention, while many other important issues (e.g., multiannual density changes, competition with native organisms, predation by invertebrates, reptiles, birds, and mammals) lag far behind. The effects of the golden mussel on environmental traits and resident organisms have been investigated almost exclusively in laboratory or mesocosm settings, but extrapolation of these results to waterbody scales is contentious, mainly because system-wide densities are largely unknown. The information available suggests that most environmental impacts of L. fortunei are mixed, context- and stakeholder-dependent, with both positive and negative effects. In contrast, its impacts on human-made facilities and infrastructure are clearly always negative and costly.
Traits that independently evolve many times are important for testing hypotheses about correlated evolution and understanding the forces shaping biodiversity. However, population genetics processes can cause hemiplasies (traits determined by genes whose topologies do not match the species tree), leading to a false impression of convergence (homoplasy) and potentially misleading inferences of correlated evolution. Discerning between homoplasies and hemiplasies can be important in cases of rapid radiations and clades with many gene tree incongruences. Here, focusing on two-clawed spiders (Dionycha) and close relatives, we evaluate if the observed distribution of characters related to a web-less lifestyle could be better explained as synapomorphies, homoplasies, or hemiplasies. We find that, although there are several convergences, hemiplasies are also sometimes probable. We discuss how these hemiplasies could affect inferences about correlation and causal relationship of traits. Understanding when and where in the tree of life hemiplasy could have happened is important, preventing false inference of convergent evolution. Furthermore, this understanding can provide alternative hypotheses that can be tested with independent data. Using traits related to the climbing ability of spiders we show that, when hemiplasy is unlikely, adequate model testing can be used to better understand correlated evolution, and propose hypotheses to be tested using controlled behavioral and mechanical experiments.
The Yabotí Biosphere Reserve (Prov. Misiones, Argentina) with 221,155 ha, represents one of the southernmost relicts of the Paranaense forest. Currently, a project is being developed in the area to inventory and describe the ferns and lycophytes. As a result of these studies, we identify a new species of Amauropelta, A. yabotiensis. Within this genus, it belongs to the group of species with uncinate hairs and presents a unique combination of diagnostic features, including the type of pubescence on the rhizome scales, the shape of the fronds and segments and type of venation. Here, we described and illustrated the species and we analyzed its taxonomic affi nities and geographic distribution. Additionally, we provided a distribution map and a key to distinguish it from other Amauropelta species from Misiones province. With this new fi nding, we highlighted the importance of the Yabotí Reserve as a reservoir of biodiversity in the region.
Sulforaphane (SFN) is an isothiocyanate-type phytomolecule present in crucifers, which is mainly synthesized in response to biotic stress. In animals, SFN incorporated in the diet has anticancer properties among others. The mechanism of action and signaling are well described in animals; however, little is known in plants. The goal in the present study is to elucidate components of the SFN signaling pathway, particularly the production of reactive oxygen species (ROS), and its effect on the transcriptome. Our results showed that in Arabidopsis, SFN causes ROS production exclusively through the action of the NADPH oxidase RBOH isoform D that requires calcium as a signaling component for the ROS production. To add to this, we also analyzed the effect of SFN on the transcriptome by RNAseq. We observed the highest expression increase for heat shock proteins (HSP) genes and also for genes associated with the response to oxidative stress. The upregulation of several genes linked to the biotic stress response confirms the interplay between SFN and this stress. In addition, SFN increases the levels of transcripts related to the response to abiotic stress, as well as phytohormones. Taken together, these results indicate that SFN induces an oxidative burst leading to signaling events. This oxidative burst may cause the increase of the expression of genes such as heat shock proteins to restore cellular homeostasis and genes that codify possible components of the signaling pathway and putative effectors.
Abelisaurids are medium–large-sized theropod dinosaurs that were predominant in the carnivorous fauna during the Late Cretaceous of Gondwana. These predators are abundant in the Cretaceous fossil strata of Patagonia, which yield the best record for this group. In the Late Cretaceous, abelisaurids appear in almost all regions of Gondwana and in all stages, except for the Coniacian, in which they are globally unknown. Here we describe a new abelisaurid, Elemgasem nubilus gen. et sp. nov., from the Portezuelo Formation (Turonian–Coniacian), Patagonia, Argentina. The palaeohistology of the appendicular bones of Elemgasem shows that the holotype was a subadult individual, but had achieved sexual maturity. This taxon is based on several axial and appendicular elements, and is diagnosed by the presence of a marked pattern of rugosity on the lateral surface of the fibula and a dorsoventrally deep lateral wall of the calcaneum. Moreover, the posterior caudal vertebrae have a morphology slightly different from any other abelisaurid. Elemgasem nubilus is recovered as an unstable taxon within Brachyrostra, given that it was recovered as sister taxon of Furileusauria or in several positions within this clade. Despite the problematic phylogenetic relationships of Elemgasem nubilus, it is important because it is the first abelisaurid from the Turonian–Coniacian interval and it increases the diversity of this theropod family at a time of marked turnover in the tetrapod fauna of South America, global climate change, and mass extinction events recorded worldwide in the marine realm.
The ENSO (El Niño-Southern Oscillation) phenomenon affects, through climate teleconnections, hydrometric variables of water bodies worldwide, influencing biota communities. The aim of this work is to analyze ENSO effects on water discharge, water level, cyanobacterial blooms and, consequently, on the reproduction of migratory fishes with high-frequency monitoring of ichthyoplankton data from Salto Grande, a large South American reservoir. Two highest peaks of ichthyoplankton density were observed; the first one (2015–2016) occurred during a very strong El Niño event, while the second one (2019–2020) was preceded by weak El Niño events that lasted 18 months. These results suggest that ichthyoplankton abundance may be affected by the intensity and temporal extent of the episodes. In contrast, mean fish larval and egg densities were reduced by 65% and 85%, respectively during La Niña periods. Cross-correlation function (CCF) analysis indicates that water discharge, water level, and ichthyoplankton abundance were positively related to the Oceanic Niño Index, while cyanobacteria showed an inverse relationship. Cyanobacterial density increased by 574% during La Niña compared with El Niño events. Based on an uninterrupted monitoring of ichthyoplankton over 11 years, it seems reasonable to consider ENSO as a predictive tool for the intensity of reproductive activity of migratory fishes.
The Cenomanian–Turonian is considered the warmest interval of the last 150 million years. It was characterized by major disturbances to the global carbon cycle, resulting in elevated pCO2 levels and global temperatures, and witnessed the rise to dominance of angiosperms floras. In this paper, we assess changes of fossil floras during the Cenomanian–Turonian interval based on palynological studies of two distantly-spaced localities in high southern paleolatitudes: the Mata Amarilla Formation of Patagonia, southern South America and the Tupuangi Formation of the Chatham Islands, New Zealand. Richness estimations for each stratigraphic unit and cluster analysis were conducted to assess the vegetation changes. Palynological dominance and the presence/absence of taxa were compiled for these units and compared with others from the Cenomanian of southern Gondwana. We recognize a peak in richness during the Mid-Cenomanian Event in Patagonia, with a fall in richness after the event due to species being displaced by dominant taxa. Several richness peaks are also recognized in New Zealand, but the lack of stratigraphic control prevents correlation with marine-based events. Oceanic Anoxic Event 2 is not recorded in either study area. The inclusion of Gondwanic palynological records demonstrate that the Tupuangi Formation cluster with sites from the Antarctic Peninsula and south-eastern Australia conforming a ‘polar cluster’. However, this area has its own palynological signature, constituting a newly proposed Taxodiaceaepollenites Subprovince. The abundances of key plant groups of the Mata Amarilla Formation cluster with those of Bathurst Island (northern Australia), but also show important differences, likely owing to their geographic separation and latitudinal difference. This work actualizes the Southern Gondwana palynological provinces scheme for the mid-Cretaceous and provides novel data sets for Patagonia and New Zealand which can be use as reference on palynological and paleoecological studies of coeval floras worldwide.
Oligoryzomys longicaudatus se distribuye por las laderas orientales y occidentales de los Andes en el extremo sur de Sudamérica. En el sur de Argentina presenta una distribución relativamente bien conocida, pero hacia el norte, en coincidencia con la existencia de poblaciones aparentemente discontinuas, sus límites geográficos no están bien establecidos. Durante una revisión de especímenes de Oligoryzomys depositados en la Colección Mamíferos Lillo registramos dos ejemplares provenientes de la provincia de San Luis que fueron asignados a esta especie a partir de comparaciones cuantitativas y cualitativas del cráneo. Sobre estos ejemplares, citamos por primera vez a la especie para esta provincia y el Chaco Seco, destacando la importancia del registro para el conocimiento de su distribución.
The aim of this study was to evaluate the toxic effects of the pesticide cypermethrin (CYP) in the digestive gland of the apple snail, Pomacea canaliculata, analysing histological and histochemical alterations. Adult snails were exposed to sublethal CYP concentrations (10, 25, and 100 µg/L) under acute (1 day) and sub-chronic (14 days) conditions. Histological analyses of the morphology of the digestive gland were performed and a histopathological condition index (HI) was calculated. Also, both intracellular accumulation of lipofuscins (LF) and neutral lipids (NL) were evaluated. CYP exposure induced tissue damage to this organ, such as disorganisation of the connective tissue, fibrosis, haemocytic infiltration, atrophy, and necrosis under acute and sub-chronic conditions. These alterations, integrated into a single HI value, revealed notable CYP effects during both acute and sub-chronic exposures. Cell type replacement, measured as VvBAS, was only observed in the sub-chronic treatment. Under acute conditions, the pyrethroid affected NL accumulation at the highest concentration, while in sub-chronic conditions NL accumulation was only observed at the lowest concentrations. P. canaliculata also showed a dose-dependent response of LF under acute CYP exposure conditions. However, under sub-chronic conditions, this parameter was not sensitive to pesticide exposure. All these relevant structural lesions may affect the normal function of the digestive gland, even though the species presented additional mechanisms, as infiltration of hemocyte and basophilic cell hyperplasia, that help it to tolerate the exposure to pollutants. This study showed that some histological and histochemical parameters are sensitive in P. canaliculata at CYP concentrations to which the snail could be exposed in the environments it inhabits.
Argentina, an extensive country located in southern South America, encompasses a considerable range of latitude and altitude, with a high diversity of lowland and highland waterbodies. Our study is aimed at providing information regarding the current taxonomic diversity of the main groups of the country’s inland-water zooplankton. A total of 242 Protozoa, 375 Rotifera Monogononta, 170 Cladocera, and 120 Copepoda species and subspecies are reported. We submit considerations of the current level of taxonomic knowledge, the regional distribution of the species, and the biogeographical (or zoogeographical) aspects. Since most research was focused on a few regions or a small number of water bodies within large regions, many habitats have been scarcely studied, particularly in areas with wide seasonal or interannual variability. We assume that the potential species number in all groups is much higher than currently recognized. Further studies at wider spatial and temporal scales and at a higher taxonomical resolution as well, are needed in order to provide a full picture of the zooplankton diversity of Argentina.
Aim Mountains cover approximately 22% of the planet's terrestrial surface and have dramatic effects on climate and biodiversity. The rain shadow effect is a common feature on mountain ranges worldwide and its effects on ecology and evolution of species, particularly morphology, are incompletely known. Our aim is to identify the correlates that best describe morphological variation along a pronounced rain shadow gradient. Location Patagonia and Tierra del Fuego (southern South America), including Valdivian and Magellanic forests and steppes. Taxa Shaggy soft-haired mouse Abrothrix hirta (Order Rodentia, Family Cricetidae). Methods We measured 450 skulls of A. hirta from 67 localities between 35°S and 54°S, from the Pacific to the Atlantic coasts. We analysed geographic differences in skull morphology using 17 linear skull measurements. Discriminant function analysis revealed clear evidence for sexual dimorphism; thus, analyses were conducted for the entire dataset, and separately by sex. We implemented regression tree analysis to test the environmental correlates that best describe morphological variation along this gradient. Results Skull size variation in shaggy soft-haired mice does not follow Bergmann's rule; however, latitude was the second node for PC1 of all samples. Regression tree analyses showed that the variables that best explained size for the various datasets were longitude, precipitation of the coldest quarter and temperature seasonality. Longitude appeared in eight of the nine regression tree analyses. We find that organisms attain greater sizes in the western Andes where there is no rain shadow effect, below 500 m of elevation. Main Conclusions Morphological variation and size of A. hirta is highly structured along a longitudinal gradient, which mirrors patterns of primary productivity and the Andean rain shadow effect in this region, best described by the “resource rule”. Mountains are a formidable land feature that clearly affects the morphology of species distributed at both sides of them.
The fossil record of condors in South America is relatively extensive. However, fossil specimens from the late Pleistocene of Argentina are still very scarce. Here, we describe fragmentary remains of a large sized cathartid of the condor lineage. The new specimen is represented by an incomplete ulna, radius and metacarpal belonging to the Lujanian (Late Pleistocene) of San Pedro locality, Buenos Aires, Argentina. Its large size (it is among the largest cathartids reported up to the date) and some anatomical details indicate that it belongs to a previously unrecognised taxon. The new specimen reinforces previous proposals indicating a high diversification of condors at South American lowlands, and indicates that the Pleistocene history of the clade is far from being satisfactorily known. The extinction of giant scavenger birds in South America may be not only related to the extinction of their food resources (i.e., megafauna) but also to ecological constraints that characterise large-sized birds.
Aim: Some species have populations that vary in ecologically relevant traits along environmental gradients, which is a pattern often generated by secondary contact post divergence in allopatry. However, an alternative explanation for such a pattern would be primary contact, where populations diverge in the presence of gene flow through the action of strong natural selection. We aimed to test the divergence-with-gene-flow model across an environmental gradient in a Chaco-Andes dry forest bird. Location: Central Andes Mountain range and Chaco region of Argentina and Bolivia. Taxon: Phytotoma rutila (Aves, Cotingidae). Methods: We generated ddRADseq loci for 23 individuals and obtained body size variation data for 146 museum specimens. We evaluated population genetic structure and tested the effects of elevation and isolation by geographic distance on genomic divergence. To distinguish divergence in allopatry from divergence-with-gene-flow, we compared the divergence of phenotypic traits (bill, tarsus and wing) with neutral genomic variation (S-test and P ST-F ST comparisons), conducted coalescent analyses to estimate gene flow and divergence time, and calculated relative (F ST) versus absolute (D XY) genomic divergence. Results: We found (a) P. rutila differs genomically and phenotypically following the highland-lowland axis of the study region, with altitudinal variation explaining genomic variation; (b) larger phenotypic than neutral genomic divergence; (c) asymmetric gene flow between Andean and Chacoan populations; and (d) a pattern of relative and absolute genomic differentiation compatible with divergence-with-gene-flow. Main conclusions: The mechanism behind the morphological and genomic diversification along the Chaco-Andes dry forest belt in P. rutila is divergence-with-gene-flow. Diversification in South America implicates gene flow between populations and natural selection following environmental gradients, as well as vicariance. This complex combination contrasts with the traditional idea that speciation in birds occurred primarily in allopatry. K E Y W O R D S Andes, Chaco, dry forest, natural selection, parapatric divergence, Phytotoma rutila
With c. 24 700 species (10% of all flowering plants), Asteraceae are one of the largest and most phenotypically diverse angiosperm families, with considerable economic and ecological importance. Asteraceae are distributed worldwide, from nearly polar latitudes all the way to the tropics, and occur across a diverse range of habitats from extreme deserts to swamps and from lowland rainforests to alpine tundra. Altogether, these characteristics make this family an outstanding model system to address a broad range of eco-evolutionary questions. In this review, we summarize recent progress in our understanding of Asteraceae on the basis of joint efforts by specialists in the fields of palaeobotany, cytogenetics, comparative genomics and phylogenomics. We will highlight how these developments are opening up new possibilities for integrating fields and better comprehending evolution beyond Asteraceae.
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173 members
Ezequiel Ignacio Vera
  • Paleobotánica
Silvia N. Cesari
  • Paleobotany
Nicolas Chimento
  • Laboratorio de Anatomía Comparada y Evolución de los Vertebrados
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Buenos Aires, Argentina