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Environmental heterogeneity shapes the traits of natural populations, including space use and burrowing behavior. We studied the red viscacha rat (Tympanoctomys barrerae), a semifossorial rodent with patchy distribution in drylands of west-central Argentina, to provide ecological data on habitat and burrow features of this specialist species. We collected data on 165 burrows and 55 individuals from 2017-2018 and observed correlations between different vegetation types, vegetation diversity, and physical attributes (e.g., soil hardness). A high number of individual red viscacha rats was negatively associated with herbs. The number of burrow entrances was positively associated with harder soils and negatively associated with vegetation cover. Our results suggest that the species' patchy distribution is strongly associated with environmental heterogeneity of these arid environments, and consequently provide an essential step towards conserving their populations across their geographic range. [ABSTRACT FROM AUTHOR]

Rodents are an important component of South America fauna. Their high diversity has motivated researchers to continually review their taxonomy, genetic diversity, species limits, and phylogenetic relationships. Here, we applied DNA‐barcodes for assessing the taxonomic and genetic diversity in the two major lineages of South American rodents: caviomorphs and sigmodontines. We analysed 335 COI barcodes in 34 morphologically determined species from 39 localities along central Andes and arid lands of Argentina. Neighbour‐joining and maximum likelihood reconstruction provided clear separation between species. The Barcode Index number and Bayesian Poisson tree processes were used to confirm concordance between sequence clusters and species designations by taxonomy. We found deep divergence within the Phyllotis xanthopygus species complex, with distances up to 13.0% between geographically separated lineages. Minor divergences (3.30% and 2.52%) were found within Abrothrix hirta, and Tympanoctomys barrerae, respectively, with differentiation in their genetic lineages. Also, we documented geographically separated clusters for Akodon spegazzinii and A. oenos with up to 2.3% divergence, but clustering methods failed to distinguish them as different species. Sequence results show a clear barcode gap with a mean intraspecific divergence (0.56%) versus a minimum nearest‐neighbour distance averaging (10.1%). Distances between congeneric species varied from 4.1 to 14%, with the exception of two related forms within Euneomys and the sister species Akodon spegazzinii and A. oenos. This study constitutes a substantial contribution to the global barcode reference library. It provides insights into the complex phylogeographic patterns and speciation scenarios in rodents, while highlighting areas that require in‐depth taxonomic and integrative research. [ABSTRACT FROM AUTHOR]

Assemblage patterns could be primarily generated by two types of drivers: exogenous (such as environmental and climatic factors) and endogenous (interactions such as competition, predation, mutualism or herbivory). The most widely accepted hypothesis states that at smaller scales (such as patch scale), interspecific interactions are the major drivers structuring communities, whereas at larger regional scales, factors such as climate, topography and soil act as ecological filters that determine assemblage composition. The general aim of this paper is to compare different exogenous drivers in terms of their relative dominance in structuring desert small mammal communities across a range of spatial scales, from patch to regional, and compare them with previous results on endogenous drivers. Our results show that as spatial scale increases, the explanatory power of exogenous factors also increases, e.g. from 17% at the patch scale (i.e. abundance) to 99% at the regional scale (i.e. diversity). Moreover, environmental drivers vary in type and strength depending on the community estimator across several spatial scales. On the other hand, endogenous drivers such as interspecific interactions are more important at the patch scale, diminishing in importance towards the regional scale. Therefore, the relative importance of exogenous versus endogenous drivers affects small mammal assemblage structure at different spatial scales. Our results fill up a knowledge gap concerning ecological drivers of assemblage structure at intermediate spatial scales for Monte desert small mammals, and highlight the importance of dealing with multi-causal factors in explaining ecological patterns of assemblages. [ABSTRACT FROM AUTHOR]

In drylands livestock grazing is the main production activity, but overgrazing due to mismanagement is a major cause of biodiversity loss. Continuous grazing around water sources generates a radial gradient of grazing intensity called the piosphere. The ecological sustainability of this system is questionable and alternative management needs to be evaluated. We apply simple indicators of species response to grazing gradients, and we propose a novel methodological approach to compare community response to grazing gradients (double reciprocal analysis). We assessed degradation gradients of biodiversity under different management strategies in semiarid rangelands of the Monte desert (Argentina) by analyzing changes in vegetation, ants and small mammal richness and diversity, and variation due to seasonality. At the species level, we determined the trend in abundance of each species along the gradient, and the potential cross-taxa surrogacy. At the community level, the new methodological consists of assessing the magnitude of biodiversity degradation along different piospheres by comparing the slopes of linear functions obtained by the double reciprocal analysis. We found that most species showed a decreasing trend along the gradient under continuous grazing; while under rotational grazing fewer species showed a decreasing trend, and a neutral trend (no change in the abundance along the gradient of grazing intensity) was the most common. We found that vegetation cannot be used as a surrogacy taxon of animal response. Moreover, weak cross-taxa surrogacy was found only for animal assemblages during the wet season. The double reciprocal analysis allowed for comparison of multi-taxa response under different seasons and management types. By its application, we found that constrains in precipitation interacted with disturbance by increasing the negative effect of grazing on vegetation, but not on animal assemblages. Continuous grazing causes biodiversity loss in all situations. Rotational grazing prevents the occurrence of vegetation degradation and maintains higher levels of animal diversity, acting as an opportunity for biodiversity conservation under current scenarios of land use extensification. Our approach highlights the importance of considering multi-taxa and intrinsic variability in the analysis, and should be of value to managers concerned with biodiversity conservation. [ABSTRACT FROM AUTHOR]

This study aims to analyze dryland dynamics under livestock production in an integrated manner, by considering several taxa, intrinsic variability in resource availability and variations in disturbance intensity and management. Resilience was assessed by quantifying functional redundancy and response diversity of vegetation, ants and small mammals in arid rangelands under continuous and rotational management strategies. The net effect of increasing grazing intensity on community resilience and the occurrence of structural (richness, diversity and composition) and functional (decomposition rate) threshold responses under the effects of seasonality and management were assessed. Results showed that grazing intensity negatively affected functional redundancy more than response diversity of all taxa and under both management strategies. Animal assemblages showed abrupt changes in richness and diversity, but vegetation showed a gradual change in structure along the grazing intensity gradient. Decomposition rate showed abrupt changes under both management strategies. Although overall community resilience decreased, not all assemblages presented a threshold response, probably due to different components of resilience affecting assemblages in different ways. These decreases caused structural threshold response within animal taxa but not on vegetation. The lack of thresholds in vegetation does not imply that a related ecosystem process is not affected (i.e., decomposition). Vegetation and animal assemblages, as well as functional and structural threshold responses, may not be strongly coupled in natural systems. [ABSTRACT FROM AUTHOR]

Much of South America consists of diverse arid and semiarid regions characterized by high mammal endemism as a result of a complex interplay between place and lineage histories. In this review we summarize and highlight several biogeographical and ecological features of the small mammals of South America drylands, with special focus on the Monte Desert biome. We provide information on population characteristics, community structure, food and habitat use, and responses to disturbances. Major findings at different scales include the distinctiveness and high species turnover across South American drylands and Monte Desert ecoregions; synchronous population fluctuations with high variability between years; herbivory and omnivory as dominant trophic strategies; community structure organized through habitat and food segregation; and the importance of a landscape mosaic of grazed and ungrazed areas for maintenance of small and medium-sized mammal diversity. [ABSTRACT FROM AUTHOR]

Space use in deserts usually has been considered only along the horizontal dimension; however, vertical structure could be an important variable for habitat segregation among small mammal species. Our study assessed the use of vertical space by small mammals of the Monte Desert by live-trapping animals at different heights. We recorded 1,336 captures of 4 rodent and 1 marsupial species in 27,600 trap nights. All 5 species were captured on the ground and in tree layers, but only the gray leaf-eared mouse (Graomys griseoflavus) and the desert mouse opossum (Thylamys pallidior) used vertical space appreciably. G. griseoflavus used the arboreal space independently of habitat, plant species, or branch diameter, whereas T. pallidior showed a more selective behavior, being present at greater heights and on large-diameter branches of Prosopis trees. All rodent species used lower more than higher parts of arboreal strata. They used vertical space more or only during the dry season when resource availability is low. Our study suggests that vertical structure offers greater opportunities to acquire resources when these are scarce and plays a role in the coexistence of small desert mammals. [ABSTRACT FROM AUTHOR]

It is becoming more apparent that species richness alone many not be sufficient to fully understand ecosystem resilience but that functional diversity (diversity of species having similar effects on an ecosystem process) may be more relevant. In particular, response diversity (diversity of species that respond differently to disturbance) within functional groups (FG) is suggested to be critical for resilience. We assess for the first time the use of response diversity as a measure of resilience in an empirical study. Our experimental design consisted of sites with three disturbance intensities during a grazing exclosure period and the same sites, 1 year later, after grazing. Plant FGs were identified based on effect traits related to nutrient cycling and soil retention, and species richness within groups was assessed during exclosure and after grazing. To assess if response diversity could predict loss of species richness (resilience analysis), response diversity was calculated only during the exclosure period, based on traits related to grazing tolerance. We also assessed the contribution of richness to response diversity during exclosure (redundancy analysis). Response diversity was significantly and highly correlated with species richness within FGs during disturbance. That is, FGs with the lowest response diversity were the most affected, disappearing when disturbance appeared. Richness within FGs during exclosure was not significantly correlated with response diversity, showing that higher richness does not ensure resilience. We conclude that response diversity can be used to predict which FGs are more resilient, and hence, less vulnerable to future disturbance. [ABSTRACT FROM AUTHOR]

Abstract Seed availability may limit the size of granivorous bird populations, particularly in desert environments. Seasonal and annual fluctuations in the abundance of granivorous birds were studied at three sites in the Northern Monte Desert, Argentina. The way in which these changes were related to seed supply was also studied. Granivore abundance and biomass, as well as seed abundance, were greater in winter. Changes in total granivore abundance were mostly because of variations in numbers of the most mobile bird species, all of which were found to have similar patterns of variation in their abundance. Evidence suggests that during the non-breeding season, the most mobile species are able to track patches of high seed availability over long distances, whereas the abundance of less vagile species largely depends on the local ecological conditions. Seed supply is a proximate factor that limits the abundance of granivorous birds in the Monte Desert during the winter, but does not limit species richness. Granivore abundance was not correlated with seed supply in spring. [ABSTRACT FROM AUTHOR]

Abstract: Competitive interactions are known to be stronger between morphologically similar and phylogenetically closely related sympatric species. Patagonian mara (Dolichotis patagonum) and Chacoan cavy (Pediolagus salinicola) are two medium-sized herbivorous mammals which have disjunctive distributions within a sympatric region characterized by dry woodlands and shrublands (Dry Chaco, Argentina). The niche partition hypothesis predicts that ecologically similar species living together should show differentiation in at least one of the main niche dimensions to avoid competition. Thus, we predict that Patagonian mara and Chacoan cavies will differentiate in the use of trophic and/or spatial niche. To prove this hypothesis, we sampled 26 study sites in the dry and wet season and collected fresh faeces of both species. We estimated the diet composition using microhistological analysis of faeces. For habitat analysis we measured 16 vegetation variables, as well as habitat complexity and heterogeneity structure. Our results showed that during the dry season, both species segregate their diet but not their habitat niche, whereas during the wet season they segregate their habitat, and diet segregation is diffused. Diet overlap was similar between seasons, indicating a change in the foraging strategy of the cavy, which selected forbs, grasses, succulents and trees in the dry season and only grasses in the wet season. Our results support the niche partition hypothesis as a mechanism of coexistence among ecologically similar species in the South American temperate arid lands. [ABSTRACT FROM AUTHOR]

Abstract: The wild boar, Sus scrofa, was introduced in the central region of Argentina in the early 20th century. A small feral population invaded the western area of the Man and Biosphere Reserve of Ñacuñán, Argentina in the early 1980’s. The purpose of our study was to provide information about the diet of wild boars in the semiarid region of Argentina and to assess their potential effect on vegetation through soil rooting. We analyzed 41 faecal samples and compared cover plant composition between rooted and non-rooted soil. Ninety-five percent of the wild boar diet consisted of different parts (leaves, stems, glumes, fruits, seeds, and bulbs) of 36 plant species, while arthropods and animal tissue represented only 5% of the diet. Two plant species (Sphaeralcea miniata and Pitraea cuneato-ovata) composed the bulk of the diet, representing almost 50% of the total items found in the faeces. Plant cover was significantly different between rooted and non-rooted areas. Rooted areas were dominated by Pitraea cuneato-ovata, whereas the cover of Lycium sp was higher in non-rooted areas. This is the first study addressing the ecology of the wild boar in a protected area of the Monte Desert biome of Argentina. [Copyright &y& Elsevier]