Patagonian Steppe Research Articles

Grassland biodiversity

Grasslands comprise one of Earth's dominant biomes, accounting for up to 40% of its terrestrial area (Figure 1). The fundamental components of grassland habitats are grasses and grass-like plants, but diverse assemblages of other plant life forms and diverse animal communities also contribute to grassland biodiversity. Grasses have evolved traits allowing them to cope with climatic extremes, specific soil conditions, fires, and herbivory, all of which sustain grasslands by limiting the establishment, survival, growth, and dominance of woody vegetation. Grasslands occur in almost all climatic zones, except the poles, extreme arid zones, and the highest mountains (Figure 1). Temperate grassland habitats include Eurasian steppes, North American prairies, the pampas lowlands of South America, and Patagonian steppe. Tropical and subtropical grasslands (savannas) occur mostly in Africa and Australia, but are also found in the north of South America, in the southern United States, South Asia, and Southeast Asia.

Homogenization of Macroinvertebrate Assemblages and Asiatic Clam Corbicula fluminea Invasion in a River of the Arid Patagonian Plateau, Argentina

Fil: Labaut, Yeny. Universidad Nacional de Rio Negro, Instituto de Investigacion en Paleobiologia y Geologia. Rio Negro, Argentina.

Homogenization of Macroinvertebrate Assemblages and Asiatic Clam Corbicula fluminea Invasion in a River of the Arid Patagonian Plateau, Argentina

The invasion of the Asiatic clamCorbicula flumineain South America has already reached Patagonia. Despite the well-known direct and indirect impacts that this species exerts on fresh-water ecosystems, particularly on benthic communities, few studies have been undertaken on its effect on the composition and structure of aquatic macroinvertebrate assemblages. This study evaluated the effects of the invasion of the Asiatic clamC. flumineaon the aquatic macroinvertebrate assemblages of the Limay River, one of the most important rivers of the arid plateau of Argentinian Patagonia. As this river is currently in the process of being invaded, it was possible to compare invaded and non-invaded sites. Invaded sites displayed a certain homogenization of their constituent species and functional composition. Non-metric multidimensional scaling, similarity analysis and similarity percentages showed negative or positive influence of the presence of this species on the abundance of some taxa, due to competition for resources in this low-productivity Patagonian ecosystem. The deposition of the faeces and pseudo-faeces ofC. flumineaenriches the organic content of the sediments. However, its pedal feeding can function as a competitive strategy: by consuming its own deposited organic matter when food is scarce, the amount available to other macroinvertebrates is reduced. This paper is the first contribution on the impact of this invasion on northern Patagonia’s aquatic macroinvertebrate assemblages.

Occurrence of kleptoparasitic sarcophagid flies (Diptera: Sarcophagidae: Miltogramminae) in natural and human modified sites in Southern South American Andean landscapes

Sarcophagid flies belonging to the subfamily Miltogramminae are mainly kleptoparasites of bees and solitary wasps. Twenty-six locations were surveyed to accomplish the first specific exploration on the diversity of Miltogramminae in southern Andean areas of South America. We evaluated changes in abundance, richness and composition among habitat types to establish the effect of anthropization on the Miltogramminae community. Habitat types were considered as human modified (trails and roads, parks and meadows) and natural sites (watercourses and lake beaches, sandy and shrubby areas), distributed in two ecoregions (Valdivian forest and Patagonian steppe). We found differences in the capture rate and composition of Miltogramminae among habitat types. The species Opsidia intonsa Aldrich was highly dominant in samples, with higher proportional abundance in human modified habitats. Richness of Miltogramminae was higher in natural sites. Comparisons between the ecoregions surveyed indicated the genus Opsidia Coquillett did not show differences in abundance between ecoregions, whereas Senotainia Macquart was more abundant in the Patagonian steppe. The results provide evidence on the significant effects of human influence on landscapes in kleptoparasitic fly diversity. Slight modifications of natural areas (as proliferation of trails or isolated houses) should be addressed to evaluate the conservation of kleptoparasitic Diptera.

Touch me carefully: a step towards understanding morphological diversity in the South American spiny sunflowers (Compositae, Barnadesioideae)

The subfamily Barnadesioideae (Compositae) is endemic to South America, comprising 10 genera and 80 species of mostly spiny herbs, subshrubs, shrubs, trees, or woody vines distributed from Venezuela to Argentina. Three genera, Dasyphyllum (27 species), Chuquiraga (22 spp.) and Barnadesia (19 spp.) contain 85% of the species, while the other seven genera (Archidasyphyllum, Arnaldoa, Doniophyton, Duseniella, Fulcaldea, Huarpea, and Schlechtendalia) are represented by up to three species each. Most species are found in xeric areas in the Andean and Patagonian regions—as in the Páramos, Puna and Patagonian steppe vegetation—with a secondary center of diversity in eastern South America. Previous phylogenetic hypotheses have clarified the relationships within the subfamily, showing that there are many non-monophyletic groups in different taxonomic ranks. As a result, taxonomic changes have been proposed over recent decades in order to reflect classifications comprising only monophyletic groups. In the present study, we provide a generic synopsis of the subfamily Barnadesioideae based on the most recent generic circumscriptions, including a key, expanded morphological descriptions, information on geographical distribution and habitat, photographs and taxonomic notes for all genera.

Dynamic of Mycobacterium avium subspecies paratuberculosis infection in a domestic-wildlife interface: Domestic sheep and guanaco as reservoir community.

Natural herbivore populations have experienced uninterrupted pressures from direct and evident domestic-wildlife interactions and competition, to indirect or less obvious ones such as pathogen transmission. Thus, pathogen spillover between wild and domestic animals is a constant concern because the domestic-wildlife interface represents the ecological frontier in which pathogen transmission takes place in both directions. In Patagonian steppe communities, extensive sheep ranching and guanaco (Lama guanicoe) populations coexist, and guanaco have shown to be infected by pathogens such as Mycobacterium avium subspecies paratuberculosis (MAP) likely transmitted from livestock. MAP causes chronic enteritis and affects mostly domestic ruminants. We evaluated MAP prevalence and pathogen shedding in both species' faeces collected in non-shared and shared sites according to presence/absence of sheep and guanaco along a year, in four different seasons (autumn, winter, and spring 2018, and summer 2019). Our results indicate that MAP circulates in both sheep and guanaco populations with self-sustained transmission; however, both species differ in their levels of competence. We detected higher pathogen shedding in sites occupied by sheep, suggesting that sheep populations may be the main source of infection for susceptible animals due to their large numbers which drive MAP dynamics.

Assessing the presence of a Burrowing Owl (Athene cunicularia) population at the southern continental limit of its distribution, Santa Cruz province, Patagonia, Argentina

The historical continental distribution of the Burrowing Owl (Athene cunicularia) in Argentina included Santa Cruz province. However, for almost a century its presence there was hypothetical, based on a few, sometimes even erroneous, published records. Its precise distribution and status were unknown. In the present study, using a combination of personal observations and surveys, critical literature review, searches in online databases (EcoRegistros and eBird), scrutiny of Facebook pages and group posts focused on Argentine and Patagonian birds and wildlife photography, and information provided by citizen scientists and ornithologists, we confirmed the current Burrowing Owl’s presence in Santa Cruz province. The species appears to be mostly localized to the city of Caleta Olivia and nearby open areas, Deseado Department, northeastern Santa Cruz province, within the Patagonian Steppe and, along the Atlantic coast, in the Mar Argentino ecoregions. Burrowing Owl breeds locally there, and individuals are seen yearlong. Although there are a few recent records of Burrowing Owl at other localities of Santa Cruz, we did not find evidence of a current broader distribution in this province, as most general bird guides and general ornithology books indicated in their distribution maps for the species. The southernmost known population of Burrowing Owls, restricted to northeastern Santa Cruz, provides a unique opportunity to monitor its progress. Furthermore, it could allow us to investigate the limiting factors and dynamics of its population in urban and natural areas of the Patagonian steppe and the Atlantic coast of Santa Cruz province.

Geographic distribution modeling and taxonomy of Stephadiscus lyratus (Cothouny in Gould, 1846) (Charopidae) reveal potential distributional areas of the species along the Patagonian Forests.

BackgroundStephadiscus lyratus (Couthouy in Gould, 1846), an endemic Charopidae from southern South America, was described from few dry shells. The distribution of this species is known on scattering occurrences, mainly from material deposited in museum collections. We provide here new information on anatomy, habitat, and microhabitat preferences and estimate the potential geographic distribution of the species to test if it is exclusively endemic to the Subpolar Magellanic Forest.MethodsFieldwork was carried out in the National Parks of the Patagonian Forests. Snails were photographed, measured, and dissected for anatomical studies; shells were studied with scanning electron microscopy. Estimation of the species geographical distribution (EGD) was obtained through correlative ecological niche modeling (ENM). We designed a calibration area a priori with known species points of occurrence in the Magellanic Subpolar Forests and borders of the Patagonian steppe. Seven bioclimatic variables of the WorldClim database were used. The best ENMs were calibrated and selected using a maximum entropy method with Maxent v3.3.3K through the R package “kuenm”. Candidate models were created by combining four values of regularization multiplier and all possible combinations of three feature classes. We evaluated candidate model performance based on significance (partial ROC), omission rates (E = 5%), and model complexity (AICc). From the best models obtained, a final model was transferred to a region “G” consisting of the calibration area plus the Valdivian Temperate Forests and whole Patagonian steppe, where we hypothesize that the species could be present. Finally, we obtained binary presence-absence maps. We quantified the proportion of the occurrence points and distribution range of S. lyratus in different land cover categories. To explore the degree of protection of S. lyratus’EGD, we quantified the proportion of its distributional range within protected areas.ResultsA be-lobed kidney, a close secondary ureter, the terminal portion of the uterus forming a compact glandular mass, and the vas deferens with a dilatation are new anatomical information that distinguishes this species. Stephadiscus lyratus inhabit cold native forest areas, mainly living on or under humid logs in contact with the ground. The main constraining variables to explain S. lyratus distribution in the EGD were BIO3, BIO12, BIO6, and BIO4. The potential area of distribution obtained almost duplicates their original range (140,454 km2) extending to the Valdivian Temperate forests mainly in Chile. Natural and semi-natural terrestrial vegetation was predominant in the potential area of distribution of S. lyratus. However, only 14.7% of this area occurs within current protected areas from Argentina and Chile. The ectothermic physiological traits of this species, low dispersal capacity, and its narrow habitat requirements turn S. lyratus into a potentially vulnerable species.

Soil Vulnerability Indicators to Degradation by Wildfires in Torres del Paine National Park (Patagonia, Chile)

Wildfires are a common phenomenon globally, nonetheless some ecosystems are more adapted than others. In this work, we show results of a study conducted in Torres del Paine National Park (Chile) that suffered a big forest fire in 2011, affecting 17,666 ha. The Park is located in the transitional forest-steppe zone whose annual rainfall varies between 300 and 1,500 mm. Plant communities goes from Patagonian steppe, pre-Andean scrub to Magellanic forest. Based on vegetation community and trying to cover all representative sectors affected by the fire, 5 areas of the park were sampled in 2019 following the transects where a vegetation recovery study has been monitored since the fire occurred. Soil parameters used to evaluate were: texture, soil water repellency (WR), organic matter (OM), and aggregation, including total content of macroaggregates (TCA) and their stability (AS). The results showed high values of OM, however three of the 5 areas showed statistically lower values of OM in burned samples. WR was present (from slight to severe) in the 75% of the samples, and without differences between burned and unburned. The correlations analyses indicated that WR is more related with the OM type than with quantity, since better correlations were obtained when only samples from the same area were included in the analyses. The results of aggregation indicated that soils have a poor structural development. The TCA varies from 16 to 50%, and the AS is not very high (average of 66%), being the highest in the area with lowest TCA and more affected by the fire and erosion processes. This suggests that the higher values of AS are a consequence of the destruction and loss of the less resistant fraction after the fire. The combination of the high sand content (low specific surface area) and high OM make them very susceptible to develop WR. Since these soils have a scarce development with a poor structure, the combination of the WR and the poor soil structure make them very vulnerable to erosion processes after the fire. Measures to protect the soils or accelerate the recovery are recommended in these areas when new human caused wildfires could occur.

Worlds apart: Location above‐ or below‐ground determines plant litter decomposition in a semi‐arid Patagonian steppe

AbstractWhile considerable attention has been devoted to how precipitation modulates net primary productivity in arid and semi‐arid ecosystems, the emergence of multi‐faceted controls on carbon (C) turnover suggests that there is much to be understood with respect to the mechanistic controls on plant litter decomposition.In the Patagonian steppe, we conducted a long‐term factorial experiment, evaluating the importance of position, litter quality, tissue origin and soil resources on rates of C turnover under natural field conditions. Leaf and root litter of dominant grass species were placed in litterbags in different positions, on the soil surface and buried at 5‐cm depth, with soil treatments of labile C, nitrogen (N) and their combination (C + N) over a 3‐year period.As predicted, leaf litter decomposed significantly (nearly sixfold) faster above‐ground than did root litter below‐ground (p < 0.001). Surprisingly, root litter decomposed significantly faster than leaf litter above‐ground (p < 0.001), and above‐ground decomposition was not strongly affected by soil resource additions. Below‐ground decomposition was largely determined by the interaction of litter quality and soil resource availability. Determining a C balance by integrating biomass allocation and primary productivity from this field site, combined with the data from this study, suggests large differences between the contribution of the above‐ and below‐ground biomass to soil organic matter (SOM) pools and a long residence time of undecomposed root litter.Synthesis. Litter position clearly emerged as the predominant variable determining C turnover in this semi‐arid steppe ecosystem, with litter quality and soil resources having significant, but more modest, effects. The near complete independence of above‐ground litter decomposition from soil resources and rapid decomposition of surface litter, coupled with the counterintuitive relationships with litter quality, suggests that, in the long term, C loss from photodegradation may result in a minimal contribution of above‐ground litter to SOM formation. These results have mechanistic implications for the distinct functionality of litter decomposition above‐ and below‐ground in semi‐arid ecosystems, and how these differential controls may alter the C balance due to future changes in climate and land use.

Alstroemeria esteparica (Alstroemeriaceae) una nueva especie para la flora del Cono Sur de Sudamérica

A morphological and cytotaxonomic analysis of Alstroemeria patagonica Phil. populations is made, from the Chilean Patagonian steppe, in order to clarify questions about the variability of this taxonomic entity. 3 populations were analyzed (Estancia Bano Nuevo, Jeinimeni and Estancia Chacabuco). A detailed morphological study was conducted on field specimens collected for this purpose, plus samples of the SGO and CONC herbaria. In addition, a cytotaxonomic study from collected populations was performed, using the chromosomes as a source of taxonomic evidence. Results were compared with data from Alstroemeria pygmaea Herb., in order to clarify the differences between these unifloral taxa and those with yellow flowers. The study results in the recognition of a new species of Alstroemeria for Chile and Argentina.

Filling Linnean shortfalls increases endemicity patterns: conservation and biogeographical implications for the extreme case ofLiolaemus(Liolaemidae, Squamata) species

AbstractLinnean shortfalls, or the discrepancy between formally described species and the number of existing species, imply noteworthy biodiversity conservation constraints. The case of Argentinian reptiles is unique in this context. The genus Liolaemus represents ~60% of the Argentine reptile fauna and has a current species description rate of 3.25 spp./year, leading to a significant increase in the number of known species. Filling Linnean shortfalls within this genus has revealed an extraordinary recent evolutionary radiation that strongly modifies the spatial accumulation patterns of richness and endemism, mainly in the Patagonian steppe and Monte ecoregions of Argentina. Thus, while 40 years ago none of the studied species was considered endemic at the ecoregional level, today the genus represents an essential element to define the southernmost terrestrial ecoregions of the world. Furthermore, the remarkable decrease in the average extent of occurrence (EOO) of Liolaemus species implies an increased extinction risk in light of threats caused by humans. Based on the thresholds for the IUCN Red List B1 criteria, and 11 well-studied clades of Liolaemus, we show that, while in 1980 87% of the described species would not qualify as threatened based on EOO, today 80% of the species have an EOO smaller than 20 000 km2. Therefore, they may qualify as threatened based on the B1 EOO thresholds, which demonstrates the importance of the recent increase of knowledge regarding the taxonomy, systematics and genetics of the group.

Development and resilience of deciduous Nothofagus forests since the Last Glacial Termination and deglaciation of the central Patagonian Andes

Resolving the history of vegetation, fire, and glaciation on the eastern slope of the central Patagonian Andes (44°-49°S) since the Last Glacial Termination (T1) has proved difficult. This is due to the steep environmental gradients, vegetation heterogeneity, and scarcity of dated glacial deposits and geomorphic features. Unsurprisingly, published records show important heterogeneities which limit our understanding of the timing and magnitude of climate and vegetation changes, and their driving mechanisms since T1. In this paper, we describe sediment cores from small closed-basin lakes located in the deciduous Nothofagus forest zone near Coyhaique, Chile. Our results indicate that the Coyhaique glacier lobe abandoned its final Last Glacial Maximum position just before ~17.9 cal kyr BP and underwent a step-wise recession that included a halt/readvance that culminated at ~16.8 cal kyr BP, contemporaneous with the formation of an ice-dammed proglacial lake in the Coyhaique/Balmaceda sector. This glacial lake stood at its highest level between ~17.9–17.2 cal kyr BP (<726 and > 650 m.a.s.l.), lowered between ~17.2–16.2 cal kyr BP (<650 and > 570 m.a.s.l.), and disappeared thereafter. Herbs and shrubs, currently dominant in high Andean and Patagonian steppe environments, colonized the ice-free terrains distal to the glacier margins and proglacial lakes under cold and dry conditions. This was followed by a steady increase in Nothofagus between ~16.6–14.8 cal kyr BP that led to the establishment of forests starting at ~14.8 cal kyr BP. The Holocene started with a sudden increase in Nothofagus and disappearance of conifers in the context of increase fire activity between ~11.7–9.4 cal kyr BP. Closed-canopy Nothofagus forests persisted virtually unaltered from ~9.4 cal kyr BP to the present day, despite frequent explosive volcanism and millennial-scale variations in fire regimes, attesting to their extraordinary postglacial resilience which contrasts with their behavior during T1. Recent large-scale deforestation by fire, livestock grazing, and the spread of non-native invasive plant species drove the fastest and largest-magnitude shifts seen during the last ~16,500 years.

Aquatic macroinvertebrates from littoral vegetated lakes in arid Patagonia: The influence of fish introduction on community structure

Abstract Wetlands in arid regions are characterized by their great heterogeneity, often including endemic species that contribute to regional aquatic biodiversity. In the Patagonian steppe, most lakes are naturally fishless and sustain a rich aquatic biodiversity, including endemics; however, many of these lakes have been stocked with Oncorhynchus mykiss (rainbow trout) during recent decades. The introduction of predatory fish into aquatic ecosystems naturally devoid of these organisms can produce profound alterations in the structure of the original communities and in the configuration of their biotic assemblages. Aquatic invertebrates play important roles in both the structure and functioning of freshwater ecosystems, including their contribution to global biodiversity and their cascading effects across ecosystem boundaries. The aim of this study was to assess the effect of introduced non‐native fish on the pleustonic macroinvertebrate assemblage. Samples were taken from 10 shallow Patagonian lakes (five fishless and five stocked with fish) in two consecutive warm periods. Lakes with fish had higher conductivity and phosphate values. Higher inter‐annual differences were also observed in lakes with fish for phytoplanktonic chlorophyll a, nitrate, phosphate, conductivity, and water temperature. The community structure (relative abundance of different taxa, species composition, and diversity index) was affected by the presence of rainbow trout, with the differences mainly driven by the relative abundance of Ostracoda, Hyalella, Chironomidae, and Haliplus species. This approach can be used to assess the required conservation actions in shallow Patagonian steppe lakes, which have been listed as priority areas for waterbird conservation. Specifically, this study provides a baseline for monitoring future trends of the macroinvertebrate communities and for evaluating conservation and management efforts over time.

A reappraisal of the species richness of Euneomys Coues 1874 (Rodentia, Cricetidae), with emendations of the type localities of Reithrodon fossor Thomas 1899 and Euneomys mordax Thomas 1912

Abstract The genus Euneomys is mostly distributed in the open environments of the central and southern Andes, adjacent Patagonian steppes of Argentina and Chile, and in several islands of the Tierra del Fuego Archipelago. This genus includes three living species: E. chinchilloides, E. fossor, and E. mordax. Euneomys fossor is a poorly known species, with an uncertain geographic provenance and known from a single specimen, whose distinction from the other species of the genus has not been accurately assessed. Here, using qualitative and quantitative morphological evidence, plus published information about karyotypes and genetic variation, we evaluate the taxonomic status of E. fossor and E. noei, a nominal form usually considered a synonym of E. mordax. Based on multivariate analysis of cranial measurements and morphological discrete traits, we recognize two main morphotypes within Euneomys, one referable to E. chinchilloides (with dabbenei, petersoni, and ultimus as synonyms), and another including E. fossor, E. mordax, and E. noei. The recognition of two major groups within Euneomys is also supported by molecular and chromosomal data. By the principle of the priority, the names of E. chinchilloides and E. fossor applies for each one of these morphotypes. In addition, after discussing the pros and cons of replacing the name mordax by fossor, we emended the type localities of both forms.

Grass recruitment constraints along a grazing gradient in Patagonia: N-limitation x adult competition trade-off

We explored the effect of N addition and adult canopy competition on the recruitment of lost preferred species in the Patagonian steppe, where a decelerated N cycling scenario (sensu Ritchie et al., 1998) had been previously detected. In the first experiment we demonstrated that the preferred scarce grass Bromus pictus has typical traits of Competitive species, while the dominant less preferred Pappostipa speciosa has typical traits of Stress tolerant species (sensu Grime, 1997): B. pictus showed higher maximum Relative Growth Rate, water consumption and competitive ability than P. speciosa. In the second experiment, we proved that without N addition, seedlings of the preferred species showed its maximum survival rate under moderate grazing, where adult competition is lower than under ungrazed conditions and N-limitation is lower than under intense grazing. Instead, with N addition, the survival rate of B. pictus was maximum under intense grazing, where N limitation is maximum and adult competition is minimum. These results suggest that in degraded systems subjected to a decelerating N cycling scenario, the revegetation with preferred species would require recovering soil N levels, and would be more successful in the most degraded sites, where the remnant canopy has low cover.

Alien plant species on roadsides of the northwestern Patagonian steppe (Argentina).

The introduction of alien species represents one of the greatest threats to biodiversity worldwide. Highway construction increases the dispersal and invasion of exotic plant species. This study examined the assembly process of the plant communities to determine whether the roadsides of the Patagonian steppe represent a reservoir and dispersal source of invasive exotic species. We analyzed the composition of exotic and native species and functional groups present in the established vegetation and seed banks of roadsides and reference areas nearby. The type of dispersal of exotic and native species at the roadsides was also evaluated. Total cover and that of exotic and native species was lower at the roadsides than in the reference areas; however, at the roadsides the cover and seed abundance of exotic species was higher than that of native species. In the roadsides vegetation, native shrubs such as Acaena splendens predominated, along with exotic perennial herbs and grasses which were mainly represented by Rumex acetosella. In the seed bank the predominant species were exotic perennial herbs, also represented by R. acetosella, annual exotic species such as Epilobium brachycarpum and Verbascum thapsus, and annual native species such as Heliotropium paronychioides. No exotic shrubs were found either at the roadsides or in the reference areas. The species at the roadsides did not present a dominant type of dispersal. The abundance of exotic species at the roadsides, both in the aboveground vegetation and the seed bank, may be due to the stressful environment and the characteristics of the species themselves, such as the ability to form seed banks. This work revealed that the roadsides of the Patagonian steppe constitute reservoirs of invasive exotic species, highlighting the importance of identifying them and controlling their spread, with a view to generating ecosystem management programs.

Role of ants as dispersers of native and exotic seeds in an understudied dryland

1. Seed dispersal by ants, i.e. myrmecochory, is important in drylands because ants may contribute to overcoming the typical resource limitation imposed on plants in these environments. Dispersal distance and directed dispersal of seeds to nutrient‐enriched ant nests benefit plants by reducing parent or sibling competition and improving growth, survival, and reproduction.2. This study investigated the role of ants as seed dispersers in the semi‐arid Patagonian steppe. In particular, this study surveyed native and exotic plants potentially dispersed by ants (i.e. those with nutritive tissues attached to seeds that could attract ants), identified seed disperser ants, and compared their effectiveness as dispersers (i.e. number of removed seeds, transport distance, and seed fate).3. It was found that 9% of plant species could be potentially dispersed by ants, and field experiments were carried out with five of them (three natives and two exotics). Six ant species dispersed seeds, with Dorymyrmex tener being the most effective seed disperser, interacting preferably with an exotic seed. Finally, the types of nutritive tissues of the seeds are important in determining the attractiveness towards different ant foraging groups.4. This study's results highlight that ant foraging group and seed's nutritive tissues are relevant traits that could help in understanding ant–seed interactions. Furthermore, in the Patagonian steppe, there are effective seed disperser ants that could play an important role in the distribution of native plants, as well as the spread of invasive species, being especially relevant in nutrient‐poor drylands due to the benefits provided by myrmecochory.

Local patterns of edaphic mesofauna distribution in the arid Patagonian steppe, Argentina

Mesofauna represents a major component of soil biological community and play a critical role in maintaining soil quality, as well as a range of ecosystem functions. A split–split plot design was performed with the aim of identifying the main predictors (phytogeographical criteria, cover type and environmental variables) of edaphic community structure under the effect of desertification. The study also aimed to examine the spatial and seasonal distribution of mesofauna community according to phytogeographical criteria (shrubland vs grassland) and cover type (bare vs covered soil) in the north-western Patagonian steppe of Argentina. The relationship between edaphic fauna, environmental variables and site location was investigated using redundancy analysis (RDA), while the main predictors of edaphic community were analysed using generalised linear mixed models (GLMMs). A total of 43 taxa of Oribatida were found in 168 samples. GLMM approaches selected cover type due to its higher effect on mesofauna community. In this sense, cover type was more important than phytogeographical criteria and environmental variables as predictor of mesofauna community. These findings contribute to a better understanding of how the distribution of mesofauna community respond in Patagonia steppe.

An avian dominance hierarchy at a supplemental water source in the Patagonian steppe.

Birds often compete and engage in interspecific agonistic interactions for access to resources such as food and breeding territories. Based on the observed outcomes from such interactions (i.e., patterns of displacements) dominance hierarchies can be established. Knowing which species can outcompete others for essential resources allows researchers to make predictions about the broader ecological impacts of interspecific interactions. We constructed an interspecific dominance hierarchy of twelve avian species which visited an artificial water source in an arid region of coastal Patagonia, Argentina. Displacements were categorized into four types, based on the behaviors involved in the interaction, and we tested if they could predict the difference in dominance between the interacting species (the difference between calculated dominance coefficients for the two focal species). Indirect displacements, involving only the arrival of the dominant species to the water source without direct aggression toward the subordinate bird, occurred more frequently between species with a large difference in dominance. The most dominant bird observed was the kelp gull (Larus dominicanus), which, due to an increasing population and expanding range, in part due to food supplementation from fisheries waste, is likely to outcompete terrestrial and marine avian species for other scarce resources.