Southern South American Research Articles

Historical and ongoing hybridisation in Southern South American grassland species.

Natural hybridisation in plants can impact genetic and morphological diversity, including the emergence of better-adapted new populations and the potential extinction of some lineages involved in this intricate process. Under progressive global warming, species often need to migrate to newly suitable areas, which may be an additional challenge for species with low dispersal ability. Throughout the search for new environments, previously allopatric lineages can come into secondary contact and eventually hybridise if reproductive isolation is incomplete. Here, we focused on two taxa representing the natural herbaceous component of southern South American lowland grasslands. We aimed to evaluate the impact of contact zones and potential hybridisation on the evolutionary relationships and population dynamics. We used single nucleotide polymorphisms and morphological data of multiple individuals from allopatric and contact zones between taxa to shed light on hybridisation patterns and demographic scenarios. Our results indicated that the contact zones impact taxa's genetic and morphological diversity, and each contact zone had different patterns of genetic diversity and morphology, constituting stable populations that potentially reflect hybridisation events occurring at distinct evolutionary times.

Southern South American Long-Distance Pollen Dispersal and Its Relationship with Atmospheric Circulation

Southern South American Long-Distance Pollen Dispersal and Its Relationship with Atmospheric Circulation

Environmental Filters Structure Cushion Bogs' Floristic Composition along the Southern South American Latitudinal Gradient.

The environmental filtering hypothesis predicts that abiotic factors restrict communities by selecting species capable of survival and persistence under specific conditions, resulting in variations in beta diversity, phylogenetic clustering, and niche differentiation among communities when studying environmental gradients. Cushion bogs and high-altitude wetlands along the Andes display homogeneous flora contrasting with zonal vegetation. Despite being influenced by microclimatic conditions, these ecosystems are subject to diverse environmental effects. Here, we test the environmental filtering hypothesis on the structure of cushion bog communities along a broad-scale latitudinal gradient from 15° S to 42° S. We analyzed 421 bogs and 293 species across three macroclimatic regions with distinct summer, winter, and transitional arid rainfall regimes. Using variance partitioning and membership-based regionalization models, we examined the impacts of climatic, edaphic, and spatial variables on beta diversity. We also assessed species' niche overlap and the influence of environmental filters on the communities' phylogenetic diversity. Results show that species turnover and niche overlap vary with macroclimatic differences, delineating three distinct regions. Notably, phylogenetic clustering in the driest part of the gradient (23° S-24° S) highlights the impact of environmental filtering. Aridity and temperature variations at a broad scale serve as environmental filters shaping the composition of bog communities across southern South America.

The phylogeographic journey of a plant species from lowland to highlands during the Pleistocene

Phylogeographic history refers to how species evolve and diversify in response to historical, ecological, and demographic factors. The climate fluctuation during the Pleistocene period marked a crucial time in shaping many species’ distribution and genetic structure, particularly those from southern South American grasslands. This work investigated the phylogeographic history of a highland grassland, Petunia altiplana T. Ando & Hashim. (Solanaceae), its diversity, and geographic distribution using a population genomic approach based on RAD-seq data. Our results indicated that, during the Pleistocene, when the grasslands expanded to highlands, the lowland populations of P. altiplana reached the higher open fields, enlarging their geographic distribution. We found that the P. altiplana genetic diversity followed the geographic division into eastern (E) and western (WE) population groups, with a subtle division in the E group regarding the Pelotas River headwater. The results also showed that isolation by distance was the main divergence pattern, with elevation playing a pivotal role in shaping WE and E groups. Our findings indicated that lowland-adapted populations quickly colonized highlands during the late Pleistocene.

Saffron-cowled Blackbirds’ reduced nest success in Argentina’s agricultural land highlights the importance of non-agricultural habitat for its conservation

Abstract The Saffron-cowled Blackbird (Xanthopsar flavus) is a globally endangered icterid endemic to the southern South American grasslands. Temperate grasslands are among the most threatened ecosystems in South America due to their high rate of land use change. In northeastern Argentina, over the last century, the conversion of natural grasslands to livestock farming, croplands, and afforestation has resulted in significant losses of breeding habitat for the Saffron-cowled Blackbird. Consequently, it has suffered severe populational declines, and its remaining populations are fragmented. In order to understand the impact of agricultural systems on the Saffron-cowled Blackbird populations, we studied its breeding biology (clutch size, hatching success, nestling production, and fledgling success) and the main parameters that influence nest survival rate in five breeding habitat types. During the breeding seasons of 2015 to 2019, we located nests and monitored their fate. We found that the cumulative probability of nest survival over the entire nesting cycle (i.e. laying, incubation, and chick rearing) was 0.06, and was lower for nests situated in grazed land covers. Conversely, nest survival was greater in breeding sites without agricultural use, particularly in marshes. Predation was the main cause of nest failure (76%), followed by brood parasitism (10%), and trampling by cattle and agricultural machinery (6%). Brood parasitism rates were higher in grazed paddocks, contributing together with predation to the failure of nests in this habitat. Our findings indicate a negative impact of livestock ranching on Saffron-cowled Blackbird reproduction. Non-agriculture habitats, such as wetlands and flooded areas, are important as refuges for nesting. Thus, the creation of breeding refuges (non-productive sites) within agricultural matrices, in association with biodiversity-friendly agricultural practices, is crucial to ensure the Saffron-cowled Blackbird’s maintenance.

A unique Late Cretaceous fossil wood assemblage from Chilean Patagonia provides clues to a high‐latitude continental environment

AbstractFossil plants, including large trunks, stems, some branches, and twigs, were collected from the Maastrichtian (68.9 Ma), upper Dorotea Formation in the Magallanes–Austral Basin, 16 km north of the Cerro Guido–Las Chinas complex in the southern Chilean Magallanes region. These fossil trunks range from 0.2 to 2.2 m in length. Petrographic slides were made in three sections (transverse, radial and tangential) and analysed under a light microscope to study the permineralized fossils. The woods and stems belong to Austroginkgoxylon gen. et sp. nov., Agathoxylon antarcticum, Podocarpoxylon paradoxi sp. nov., Podocarpoxylon mazzonii, Palmoxylon subantarcticae and Notomalvaceoxylon magallanense gen. et sp. nov. The growth rings of gymnosperms and anatomical characters of angiosperms were analysed to obtain palaeoecological data. Interactions between gymnosperm roots growing into the secondary xylem of an angiosperm (nurse logs) are recorded. The data obtained from the fossil woods suggest warm and humid conditions in this southern South American locality during the Late Cretaceous, providing a unique opportunity to study continental environments at high southern latitudes, which are poorly represented on a global scale.

Summer upper-level jets modulate the response of South American climate to ENSO

The upper-level jet stream is a critical element of atmospheric circulation, driving synoptic systems and extreme weather events. This study analyzes the impact of upper-level jets on South American (SA) summer temperature and precipitation under different El Niño-Southern Oscillation (ENSO) phases. Using the ERA5 reanalysis dataset from 1979 to 2022, we perform a daily multiparametric characterization of the jet stream, considering its spatial and temporal discontinuities. Besides latitude and intensity, we find that the departure and number of branches of the subtropical jet (STJ) and the longitudinal extent of the Pacific branch of the polar front jet (PFJ) are needed for their description. An additional parameter is required to characterize the STJ due to its absence on around 40% of summer days over SA. Moreover, we observe distinct long-term changes in PFJ parameters across different ocean basins. Three synoptic weather types (WTs) of the upper-level zonal wind are identified: normal conditions, a prominent STJ pattern, and a PFJ-only pattern. The latter pattern is associated with anticyclonic anomalies at 500 hPa in the South Atlantic Ocean and an active SA Convergence Zone, which favors clear skies and warm (wet and cold) conditions in southern SA (Brazil). Consistently, the probability of experiencing warm spells in central Argentina is increased more than twofold. Finally, we detect that the temperature anomalies associated with the WTs are independent of the ENSO phase. However, ENSO modulates the frequency of the WTs: during La Niña (El Niño), the PFJ-only (prominent STJ) pattern is more common.

Species tree analyses and speciation-based species delimitation support new species in the relict catfish family Diplomystidae and provide insights on recent glacial history in Patagonia

Diplomystidae is an early-diverged family of freshwater catfish endemic to southern South America. We have recently collected five juvenile specimens belonging to this family from the Bueno River Basin, a basin which the only previous record was a single juvenile specimen collected in 1996. This finding confirms the distribution of the family further South in northern Patagonia, but poses new questions about the origin of this population in an area with a strong glacial history. We used phylogenetic analyses to evaluate three different hypotheses that could explain the origin of this population in the basin. First, the population could have originated in Atlantic basins (East of the Andes) and dispersed to the Bueno Basin after the Last Glacial Maximum (LGM) via river reversals, as it has been proposed for other population of Diplomystes as well as for other freshwater species from Patagonia. Second, the population could have originated in the geographically close Valdivia Basin (West of the Andes) and dispersed south to its current location in the Bueno Basin. Third, regardless of its geographic origin (West or East of the Andes), the Bueno Basin population could have a longer history in the basin, surviving in situ through the LGM. In addition, we conducted species delimitation analyses using a recently developed method that uses a protracted model of speciation. Our goal was to test the species status of the Bueno Basin population along with another controversial population in Central Chile (Biobío Basin), which appeared highly divergent in previous studies with mtDNA. The phylogenetic analyses showed that the population from the Bueno Basin is more related to Atlantic than to Pacific lineages, although with a deep divergence that predated the LGM, supporting in situ survival rather than postglacial dispersal. In addition, these analyses also showed that the species D. nahuelbutaensis is polyphyletic, supporting the need for a taxonomic reevaluation. The species delimitation analyses supported two new species which are described using molecular diagnostic characters: Diplomystes arratiae sp. nov. from the Biobío, Carampangue, and Laraquete basins, maintaining D. nahuelbutaensis valid only for the Imperial Basin, and Diplomystes habitae sp. nov. from the Bueno Basin. This study greatly increases the number of species within both the family Diplomystidae and Patagonia, and contributes substantially to the knowledge of the evolution of southern South American freshwater biodiversity during its glacial history. Given the important contribution to the phylogenetic diversity of the family, we recommend a high conservation priority for both new species. Finally, this study highlights an exemplary scenario where species descriptions based only on DNA data are particularly valuable, bringing additional elements to the ongoing debate on DNA-based taxonomy.

Long‐and short‐term vegetation change and inferred climate dynamics and anthropogenic activity in the central Cerrado during the Holocene

ABSTRACTA paleoecologic analysis of pollen, macrocharcoal and trace elements from a lacustrine sediment core located at Lake Feia, central Cerrado (Goiás State, Brazil), was used to evaluate the relationship between vegetation, fire and climate during the Holocene. The development of cerrado vegetation appears to have begun 6000 years ago, initially with the establishment of an open cerrado, followed from 4800 cal a bp by a change to a woody cerrado driven by an increase in summer insolation. The increases in precipitation levels in the central Cerrado during the last 5000 years are related to the increased influence of the Amazon in central Brazil, which has facilitated biomass burning and anthropogenic activities in the region of Lake Feia. Multi‐centennial‐scale changes in water level‐related and gallery forest pollen assemblages indicate three main dry episodes, at 3440–2760, 2700–1690 and 1330–1150 cal a bp, linked to regional shifts between northern and southern South American summer monsoon boundaries. The presence of low continuous fire activity does not appear to have affected vegetation recovery, whereas two intervals with increased fire activity, at ~3300 and ~1300 cal a bp, indicated a slower recovery.

High and dry: integrative taxonomy of the Andean spider genus Nerudia (Araneae: Pholcidae)

Abstract Ninetinae are a group of poorly known spiders that do not fit the image of ‘daddy long-legs spiders’ (Pholcidae), the family to which they belong. They are mostly short-legged, tiny and live in arid environments. The previously monotypic Andean genus Nerudia exemplifies our poor knowledge of Ninetinae: only seven adult specimens from two localities in Chile and Argentina have been reported in the literature. We found representatives of Nerudia at 24 of 52 localities visited in 2019, mostly under rocks in arid habitats, up to 4450 m a.s.l., the highest known record for Pholcidae. With now more than 400 adult specimens, we revise the genus, describing ten new species based on morphology (including SEM) and COI barcodes. We present the first karyotype data for Nerudia and for its putative sister-genus Gertschiola. These two southern South American genera share a X1X2X3Y sex chromosome system. We model the distribution of Nerudia, showing that the genus is expected to occur in the Atacama biogeographic province (no record so far) and that its environmental niche is phylogenetically conserved. This is the first comprehensive revision of any Ninetinae genus. It suggests that focused collecting may uncover a considerable diversity of these enigmatic spiders.

Spatial distribution of Munida gregaria (Decapoda, Munididae) larvae in the silled Beagle Channel: Insights from spring and autumn surveys

The squat lobster Munida gregaria is an ecologically relevant species in southern South American waters. Nonetheless, fundamental topics regarding its larval ecology remain poorly studied, especially at the southern limit of its distribution area. Here, we investigated the abundance, size, and spatial distribution of M. gregaria larval stages (zoeae I-V and megalopa) in the Beagle Channel, during spring and autumn, and explored their relationships with variations in bathymetry and seawater physico-chemical properties at both sides of the Mackinlay pass sill. Plankton samples were collected from the inner sector of the channel, a fresh water-influenced and semi-enclosed system, to its mouth towards the Atlantic Ocean during four oceanographic cruises (springs of 2014 and 2015 and autumns of 2016 and 2017). Zoeae occurred throughout the study area in both seasons, with lower densities in autumn, whereas megalopae were detected exclusively in spring. The highest larval abundances and all developmental stages were found in the outer sector, where juveniles and adults also occurred. These spatial patterns were consistently observed across the different sampling dates. Contrary to previous reports, the coexistence of zoeae I-V during autumn would indicate that, at least in the outer sector, larvae that hatch late in the summer are able to reach advanced developmental stages. However, it remains unknown whether they fully develop in subsequent months. Significant associations among larval distribution patterns and environmental variables were detected, especially for late stages, which occurred mainly in the westernmost and shallowest part of the outer sector, characterized by highly stratified waters with the warmest bottom temperatures. All together, these results may reflect the effects of variations in local environmental conditions along the channel, related to bottom topography and degree of freshwater/oceanic influence, on larval cohort dynamics, adult reproduction, or both. Larvae hatched in spring were larger than those hatched in summer/autumn for all zoeal stages. Possible explanations for this finding are discussed. This study contributes to our knowledge of M. gregaria larval ecology, which is essential to understand its complex population dynamics in an environmentally complex geographical area, and to better predict its responses to climate change. • Zoeal stages I-V occurred in both spring and autumn. • Larval abundance and stage structure differed west and east of the Mackinlay sill. • Higher larval abundances and all larval stages occurred in the outer sector. • Advanced stages occurred mainly in shallow and highly stratified waters. • Larvae hatched in spring were larger than those hatched in summer-autumn.

Solitary and semisocial behaviour in the Corynura group: new findings in a clade sister to all other Augochlorini bees (Hymenoptera: Halictidae)

ABSTRACT The great diversity of social organisation present in the tribe Augochlorini makes these bees prime candidates from which to study the evolution of social behaviour. The Corynura group, sister to all other augochlorines, is comprised by three southern South American genera: Callistochlora, Corynura and Halictillus. The nest architecture and social behaviour of Ca. aureoviridis, Co. ampliata, Co. bruchiana, Co. nahuelita, H. amplilobus and H. reticulatus were studied in Argentina. Conclusive evidence of solitary and semisocial behaviour were found in a group where only communal behaviour had been confirmed. Two species presented socially polymorphic populations. Previous studies are reviewed and all data analysed considering species’ flying periods. The possibility of eusocial behaviour is briefly discussed considering environmental factors. Since some of the species visit crops, these results are useful to develop techniques to manage native bees for pollination.

A new large-sized species of Chelonoidis (Testudinidae) without gibbosities from the middle Miocene of Aguada Escondida (NW Chubut, Patagonia, Argentina).

Previously, only one small-sized species of Testudinidae (Chelonoidis gringorum) was named from Lower-Middle Miocene of Central Patagonia. In this short article, we describe a new large Testudinidae, here named Chelonoidis meridiana sp. nov. This large new species (carapace up to 80 cm) differs from other large species of the southern South American fossil record by the absence of gibbosities on neural and costal carapacial bones, a short and wide entoplastron with a humeropectoral sulcus that was placed well behind its posterior end, and pectoral scutes that are medially longer, approximately one-third of the medial length of the hyoplastra. The discovery of this new species in the Middle Miocene increases the raw turtle diversity in Chubut, permitting to reduce the gap between the raw and phylogenetic diversity previously proposed. This occurrence is also important from both a temporal and geographic point of view. It permits fixing the presence of large-sized tortoises in the continent since ~15 million years ago (Middle Miocene). This occurrence predates all other large and giant tortoises from Argentina and South America and it is older than the giant Chelonoidis from the Langhian-Tortonian of Colombia. This is also the southernmost occurrence of a large-sized testudinid in the world.

Redescription of Eurhopalothrix reichenspergeri (Santschi, 1923) stat. rev. (Hymenoptera: Formicidae), a Brazilian Atlantic Forest endemic species.

Eurhopalothrix reichenspergeri (Santschi, 1923) stat. rev. is resurrected from synonymy with E. gravis (Mann, 1922). In Brown Kempfs tribal basicerotine revision of 1960, Rhopalothrix reichenspergeri was transferred to the genus Eurhopalothrix and synonymized into the species E. gravis. Eurhopalothrix gravis became, from that moment until now, the species with the largest distribution in the genus. After the present work, E. gravis has a Central American and north South American (Colombia) distribution, while E. reichenspergeri is restricted to the Brazilian Atlantic Forest. A key to the workers of the southern South American Eurhopalothrix species is provided. The male of E. reichenspergeri is described and compared to the male of E. gravis, E. floridana Brown Kempf, 1960 and the putative male of E. spectabilis Kempf, 1962.

Large-scale variations of raptor communities in urban green spaces of neotropical cities

Urban areas are expanding continuously inducing changes in raptor communities. However, our knowledge about urbanization impacts on raptor communities at continental scales is scarce. Therefore, the aim of this study is to relate geographical (city location) and environmental characteristics of cities with raptor species richness, taxonomic composition and functional composition in urban green spaces (UGS) of Neotropical cities. Data about raptor species present in UGS was compiled through search of scientific articles and thesis in databases. Raptor species richness increased in the tropics and decreased with increasing altitude. Species richness also increased with the increasing minimum UGS size of studies. Species composition dissimilarity was influenced by altitude and the geographic location of cities, and was dominated by species turnover. Scavengers were more frequent in cities of the east coast of Brazil, whereas semi-open habitat species were more frequent in southern South American cities. Raptor body size was related positively with UGS size. The results obtained confirmed the pattern of increasing raptor species richness in the tropics. However, anthropogenic factors such as green area loss in urban areas may influence the macrogeographical patterns of raptor species richness. The species composition dissimilarity between cities is dominated by a pattern of species replacements, related to species distributions in the Neotropics. Species functional traits were affected by macrogeographical factors and also by green area size, suggesting that urbanization may alter ecosystem processes provided by raptors. In short, the conservation and planning of large UGS is fundamental to maintain raptor communities in the Neotropical cities.

Understanding Triassic tetrapod community evolution across Pangaea: Contributions from the South American record

The Triassic Period witnessed major macroevolutionary patterns among non-marine faunas including the origin and diversification of many key tetrapod linages that later dominated terrestrial ecosystems during the rest of the Mesozoic and Cenozoic. In this context, detailed knowledge of individual Triassic tetrapod fossil assemblages in a precise geochronologic framework is of upmost importance for elucidating similarities and differences in communities across biogeographic boundaries. Although, there is a bias towards data from the modern Northern Hemisphere continents, the importance and relevance of the Southern Hemisphere tetrapod fossil record has been widely recognized, particularly the record of non-mammalian therapsids (cynodonts and dicynodonts), stem turtles, non-archosaurian archosauromorphs, early crocodylomorphs, and early dinosaurs and dinosaur precursors. This volume focused in the southern South American record highlights how this outstanding fossil record, together with its temporal and paleoenvironmental context, impacts on our perception of Triassic non-marine ecosystems across Gondwana and the rest of Pangea.

Comparative electrocardiogram in two anesthetized pinnipeds, the South American fur seal (Arctocephalus australis) and the Southern sea lion (Otaria byronia), with analysis of ECG parameters allometry

AbstractThe mammalian heart has been described as a highly evolutionarily conserved structure and the cardiovascular system allometry has been fully studied among many mammalian species, but few of these studies have been focused on marine mammals. Previously reported electrocardiogram (ECG) of anesthetized Southern sea lions (SSL; n = 13) and South American fur seals (SAFS; n = 19) females were compared, and linear models were used to examine variations of ECG parameters with body mass (BM) and heart rate (HR). Electrocardiograms resulted in qualitatively similar characteristics (rhythm, polarity patterns, mean electrical axes orientation, and waves/complex forms), but there were significant quantitative differences in HR and all ECG parameters. With few exceptions, duration and amplitude parameters were significantly higher in the SSL, whereas the SAFS had a significantly higher HR. Allometric scaling was verified for most duration variables (P, T, QRS, and PR interval) and P wave amplitude, which were all significantly and positively associated with BM, with no significant effect found for HR. Results suggest that the cardiac conduction system is highly conserved, and allometry occurs for these species even in anesthetized subjects, particularly in atrial contraction and atrioventricular conduction, which was proposed as potentially related to optimal atrioventricular activation sequence and high hemodynamic efficiency.

Consumption of mate Ilex paraguariensis: a folk beverage with antioxidant power against myocardial ischemic injury

The effects of the aqueous extract of Ilex paraguariensis (Ip) and the flavonoid quercetin were tested during the induction of in vivo myocardial ischemia/ reperfusion in Rattus norvegicus. The antioxidant power of the extract and quercetin were chemically determined. The experimental groups were: control, ischemia/reperfusion induction, Ip oral treatment, Ip oral treatment and ischemia /reperfusion, quercetin oral treatment, and quercetin oral treatment and ischemia/reperfusion. Rats were anesthetized with sodium thiopental and xylazine via intraperitoneal injection and subsequently underwent 15 minutes of ischemia followed by 15 minutes of reperfusion. Ischemia was promoted by tying the left anterior descending coronary artery. Areas of risk and infarction were stained by intravenous Evans blue and triphenyl tetrazolium chloride. Reactive oxygen species (ROS), antioxidant capacity against peroxyl radicals, and lipid peroxidation of the myocardium were quantified. A significant reduction in areas of risk and infarction was detected in the ischemic myocardium treated with Ip and quercetin; ROS generation and lipid peroxidation were significantly reduced, and the antioxidant capacity was elevated. Oral administration of Ip promoted antioxidant benefits in the myocardium during ischemia and reperfusion, which reduced infarction. We suggest that Mate (a hot drink made from steeped dried leaves of Ip) consumption is a potential cardioprotective habit of indigenous people from southern South American countries, which must be better understood scientifically and ethnographically.

Seasonality and Position with Respect to the Ecological Niche Centroid are Determinants of Metabolome Expression in Eucryphia Cordifolia Cav. An Endemic Tree from the Southern South American Forests

Seasonality and Position with Respect to the Ecological Niche Centroid are Determinants of Metabolome Expression in Eucryphia Cordifolia Cav. An Endemic Tree from the Southern South American Forests

Seasonality and Position with Respect to the Ecological Niche Centroid are Determinants of Metabolome Expression in Eucryphia Cordifolia Cav. An Endemic Tree from the Southern South American Forests

Seasonality and Position with Respect to the Ecological Niche Centroid are Determinants of Metabolome Expression in Eucryphia Cordifolia Cav. An Endemic Tree from the Southern South American Forests