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Even when environmental variation over time and space is commonly considered as an important driver of population divergence, few evaluations of intraspecific genetic variation explicitly assess whether observed structure has been caused by or is correlated with landscape heterogeneity. Several phylogeographic studies have characterized the mitochondrial diversity of Abrothrix olivacea, but none has incorporated landscape genetics analyses and ecological niche modeling, leaving a gap in the understanding of the species evolutionary history. Here, these aspects were addressed based on 186 single nucleotide polymorphisms, extracted from sequences of 801 bp of Cytb gene, gathered from 416 individuals collected at 103 localities in Argentina and Chile. Employing multivariate statistical analyses (gPCA, Mantel and Partial Mantel Tests, Procrustes Analysis, and RDA), associations between genetic differences and geographic and climatic distances were evaluated. Presence data was employed to estimate the potential geographic distribution of this species during historical and contemporary climatic scenarios, and to address differences among the climatic niches of their main mitochondrial lineages. The significant influence of landscape features in structuring mitochondrial variability was evidenced at different spatial scales, as well as the role of past climatic dynamics in driving geographic range shifts, mostly associated to Quaternary glaciations. Overall, these results suggest that throughout geographic range gene flow is unevenly influenced by climatic dissimilarity and the geographic distancing, and that studied lineages do not exhibit distributional signals of climatic niche conservatism. Additionally, genetic differentiation occurred by more complex evolutionary processes than mere disruption of gene flow or drift. [ABSTRACT FROM AUTHOR]

Aim: Tropical South America, in particular Amazonia, has been identified as the area of the basal diversification of several large mammal clades. Whether this scenario also holds for younger and widely distributed clades remains unclear. Here, we assessed the historical biogeography of a young but diverse and widely distributed mammal clade. Location: The Neotropics. Taxon: Long‐tailed mice of the genus Oligoryzomys. Methods: We estimated a dated species tree by sampling five genes (one mitochondrial and four nuclear) from 30 of the 32 living species of the genus. We inferred the distribution of the most recent common ancestors (MRCAs) of distinct species groups, using a 13 ecoregion scheme and fitting three biogeographical models, to simulate dispersal events under the selected model. Results: The DEC model best explained the diversification of Oligoryzomys. The MRCA of the genus had an age of ~2.64 Mya and its ancestral area was inferred as a large region encompassing Boreal and Southern Amazonia, Chaco and Tropical Andes. Subsequent vicariance events, followed by dispersal events towards the present, account for its diversification and wide distribution. Main conclusion The biogeographical history of Oligoryzomys is complex. It originated in the northern half of South America; and then after a series of vicariant events, a series of dispersion events allowed it to colonize southern South America, the Andes and closer to the present Central and North America. This radiation, which constitutes one of the fastest and largest Pleistocene diversifications of Neotropical mammals, involves events previously suggested for other groups (e.g. Andean diversification), others that are novel for rodents and for the most part for South American mammals (e.g. the identification of the Chaco as a centre of diversification). [ABSTRACT FROM AUTHOR]

Aim: During the glacial phases, the Andean slopes of southern South America were covered by ice sheets, causing the isolation of many species in glacial refugia. This work aimed to test the number and putative location of glacial refugia in southern South America and establish the sources, timing and direction of post‐glacial colonization events. Location: Southern South America, Patagonia. Taxon: Olive mouse (Abrothrix olivacea). Methods: Using exome capture, we genotyped 7339 SNPs in 172 specimens of A. olivacea collected at 21 localities distributed across the steppe, grasslands, and forests in the Patagonian‐Fuegian region and seven specimens from two other species of Abrothrix. Based on the effective migration rate, principal component analysis, and admixture composition, we first study the population structure of A. olivacea. The source and direction of colonization events were inferred using the directionality index and standard population genetic analyses. To study the role of the glacial phases, we performed a bayesian demographic analysis to infer divergences times and ancestral population sizes. Results: Population genomic analyses based on SNPs of more than 7000 exons identified three Patagonian genetic clusters: Valdivian forests, continental Magellan forests, and a combination of continental open biomes and Tierra del Fuego. The directionality index supports a single source in northwestern forests, in line with a Valdivian forest refugium, from which the post‐glacial colonization may have started. The effective diversity rate, the onset of population expansions and divergence times also support a Valdivian forest refugium and rule out a separate southern refugium in Tierra del Fuego. Main conclusions: Our results support a coastal refugium located in or near the previously proposed Valdivian refugium and reject in situ differentiation in Tierra del Fuego. More in general, our demographical analysis reveals the role of the Last Glacial Maximum in affecting the population dynamics (i.e., contraction and expansion) of A. olivacea and in fostering the geographical diversification of populations. [ABSTRACT FROM AUTHOR]

On the flanks of > 6000 m Andean volcanoes that tower over the Atacama Desert, leaf‐eared mice (Phyllotis vaccarum) live at extreme elevations that surpass known vegetation limits. The diet of these mice in these barren, hyperarid environments has been the subject of much speculation. According to the arthropod fallout hypothesis, sustenance is provided by windblown insects that accumulate in snowdrifts ("aolian deposits"). Mice may also feed on saxicolous lichen or forms of cryptic vegetation that have yet to be discovered at such high elevations. We tested hypotheses about the diet of mice living at extreme elevations on Atacama volcanoes by combining metagenomic and DNA metabarcoding analyses of gut contents with stable isotope analyses of mouse tissues. Genomic analyses of contents of the gastrointestinal tract of a live‐captured mouse from the summit of Volcán Llullaillaco (6739 m) revealed an opportunistic but purely herbivorous diet, including lichens. Although we found no evidence of animal DNA in gut contents of the summit mouse, stable isotope data indicate that mice from elevations at or near vegetation limits (~5100 m) include a larger fraction of animal prey in their diet than mice from lower elevations. Some plant species detected in the gut contents of the summit mouse are known to exist at lower elevations at the base of the volcano and in the surrounding Altiplano, suggesting that they may occur at higher elevations beneath the snowpack or in other cryptic microhabitats. [ABSTRACT FROM AUTHOR]

The two species of the microbiotheriid marsupial genus Dromiciops (Dromiciops bozinovici: "Panchos's monito del monte" and Dromiciops gliroides: "monito del monte") exhibit a marked latitudinal genetic differentiation. Nevertheless, it is unclear whether this differentiation results from neutral processes or can be explained, to some extent, by local adaptation to different environmental conditions. Here, we used an SNP panel gathered by Rad‐seq and searched for footprints of local adaptation (putative loci under selection) by exploring genetic associations with environmental variables in the two species of Dromiciops in Chilean and Argentinean populations. We applied three methods for detecting outlier SNPs and two genotype–environment associations approaches to quantify associations between allelic frequencies and environmental variables. Both species display strong genetic structure. D. bozinovici exhibited three distinct genetic groups, marking the first report of such structuring in this species using SNPs. In contrast, D. gliroides displayed four genetic clusters, consistent with previous studies. Both species exhibited an association of their genetic structure with environmental variables. D. bozinovici exhibited significant associations of allelic frequencies with elevation, precipitation during the warmest periods, and seasonality in the thermal regime. For D. gliroides, genetic variation appeared to be associated with more variables than D. bozinovici, including precipitation and temperature‐related variables, isothermality, and elevation. All the outlier SNPs were mapped to the D. gliroides reference genome to explore if they fell within functionally known genes. These results represent a necessary first step toward identifying the genome regions that harbor genes associated with climate adaptations in Dromiciops. Notably, we identified genes involved in various functions, including carbohydrate synthesis (ALG8), muscle and neuronal regulation (MEF2D), and stress responses (PTGES3). Ultimately, this study contributes valuable insights that can inform targeted conservation strategies aimed at preserving the genetic diversity of Dromiciops in the face of environmental challenges. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Parastacus is a genus of South American freshwater crayfishes disjunctively distributed in southern Chile, Northern Argentina, Uruguay and Southeastern Brazil. Parastacus pugnax is a Chilean endemic distributed along 700 km of latitude in central-southern Chile from the Pacific coast to the Andean piedmont, which is intensively captured for consumption for local communities. Considering the habitat (wet meadows) and natural history (primary burrower, non-migrant) of the species, we tested a hypothesis of highly structured genetic diversity using mtDNA of 465 specimens gathered at 56 localities across the species range. The crown age of P. pugnax was estimated at 38 Ma, predating the main Andean uplift. The genetic variation of P. pugnax is large and geographically structured. In some cases, genetic groups do not match basin limits, suggesting a previous to current dynamic of basin evolution. The uncovered intraspecific main lineages have different demographic histories. A latitudinal cline in past effective population size reduction suggests environmental singularities with a glacial effect in the southern populations. We suggest adding morphologic and more genetic data in order to assess species limits. Our results contribute to improve future conservation actions for this taxon, providing basic information to delimit conservation units. [ABSTRACT FROM AUTHOR]

We combine morphological (qualitative and quantitative data) and genetic (one mitochondrial and one nuclear gene) data from a large set of specimens of Octodon from the four currently recognized living species of the genus. The integration of the results (qualitative assessment, multivariate analysis of cranial measurements, and gene trees) allows us to state that 1) the current taxonomic scheme does not reflect the species diversity of Octodon ; 2) in particular, as currently understood O. bridgesii likely is a complex of three species; 3) one of these, encompassing the southern populations of the genus, in the Araucanía Region (Chile) and Neuquén Province (Argentina), is named and described here as a new species; and 4) the mitochondrial gene tree departs from the nuclear gene tree with respect to O. pacificus and the new species here described. [ABSTRACT FROM AUTHOR]

The foods consumed by animals reflect their adaptations and ecological roles, which makes diet an important trait for ecological, evolutionary, and paleobiological research. Rodents are the most species‐rich order of mammals and are also ecologically diverse, consuming a wide range of foods.To relate form with function, and to study diversification in the context of diet and feeding, researchers should follow classification schemes that capture diet composition.We evaluated existing diet datasets for mammals as well as previous classification schemes developed for rodents. To propose a suitable categorical scheme, we defined splits within plant‐eating and animal‐eating rodents, aiming to capture the intrinsic differences in diet composition in terms of the accessibility, nutrient content, and digestibility of various food items.Our proposal includes eight categories (Carnivore, Folivore, Frugivore, Granivore, Omnivore, Specialist Herbivore, Unknown, and Vermivore) in which species can be assigned with information from species accounts and field guides. To avoid ambiguity, we provide examples and detailed criteria for each diet category.For biologically tractable comparative research, we ask researchers to use our diet categories for rodent species. The categories can also be applied at other taxonomic levels or to different populations, sexes, or ontogenetic stages. We call for further study of the natural history of small mammals and the uptake of primary data into open databases. [ABSTRACT FROM AUTHOR]

We reviewed the alpha taxonomy of the genus Ctenomys Blainville, 1826 in southernmost South America, with emphasis on those nominal forms previously associated with C. magellanicus Bennett, 1836. We integrate distinct lines of evidence, including variation of mtDNA sequences, and the assessment of quantitative and qualitative traits of skins and skulls; when available, karyotypic data was also considered. Phylogenetic analysis of molecular markers shows low levels of divergence among specimens from southern South American mainland and the island of Tierra del Fuego (ca. 0.4%). This evidence plus the results of the multivariate analysis of metric data suggest that the nominal forms C. colburni J. A. Allen, 1903, C. fueginus Philippi, 1880, C. osgoodi J. A. Allen, 1905, C. m. dicki Osgood, 1943, and C. m. obscurus Texera, 1975 are subjective junior synonyms of C. magellanicus. In addition, we reviewed the status of C. fodax Thomas, 1910, a nominal form that have been alternatively considered as a valid species or related to C. magellanicus by previous researchers. Based on quantitative and qualitative morphological traits, we preliminarily regard C. fodax at the species level while citing it for the first time to Chile. [ABSTRACT FROM AUTHOR]

Recently, Agnolin et al. (2019) described 14 new species of mammals, including 12 rodents, one bat, and one carnivore, and one new subspecies of rodent. In addition, these authors proposed several other nomenclatorial acts: some nominal forms were removed from synonymies and hypothesized as distinct species, at the time that three new genera, one subtribe, and one tribe of mammals were also named. We reviewed the merits of all nomenclatorial acts proposed by Agnolin at al. (2019) and concluded that all 14 new species and the new subspecies, as well as those forms removed from synonymies, should be treated as synonyms of already known species. We suggest the same regarding the three new supraspecific taxa presented by Agnolin et al., two of which are not available as they fail to comply with the provisions of the International Code of Zoological Nomenclature. We end this contribution criticizing the way that mammal taxonomy was approached by Agnolin et al. (2019). [ABSTRACT FROM AUTHOR]

Oligoryzomys, as currently understood is formed by 25 living species, is the most diverse genus of the tribe Oryzomyini of the New World subfamily Sigmodontinae of cricetid rodents. Nonetheless, the species richness of Oligoryzomys seems to be an underestimate, given some species complex has been proposed in previous studies, at the time that large geographic areas remain to be sampled, and several taxonomic forms have not been assessed with contemporary approaches. In this study, we present a new assessment of the species diversity of Oligoryzomys based on multiple unilocus species delimitation methods (ABGD, BPP, PTP, GMYC and b GMYC), using 665 cytb gene sequences as evidence (532 gathered from Genbank and 133 obtained in this study). We sampled representatives of almost all currently known species of Oligoryzomys, at the time that extending the geographic coverage to the Central Andes, a large area that was largely unrepresented in previous studies. Phylogenetic relationships, based on a non‐redundant alignment, were inferred via maximum likelihood and Bayesian inference; an ultrametric tree, used in species delimitation analyses, was obtained using multiple secondary calibration points. Results of species delimitation methods are discussed at the light of previous knowledge (e.g., taxonomic history and geographic provenance of samples in relation to type localities) and the morphological assessments of some specimens. Results of the distinct delimitation methods are mostly congruent, being BPP and PTP the most sensible to estimate species delimitation, allowing us to suggest that Oligoryzomys is composed of 30 lineages of species level. Of these, 22 correspond to forms currently considered species; some of these include in their synonymy some forms currently considered valid species (e.g., yatesi would be a synonym of longicaudatus). The remaining eight lineages are candidate species that need to be further evaluated. This study, by advancing taxonomic hypothesis that should be further tested in future studies, constitutes a stepping‐stone for upcoming taxonomic and biogeographic studies centred on Oligoryzomys. [ABSTRACT FROM AUTHOR]

With almost 2,600 species, Rodentia is the most diverse order of mammals. Here, we provide an overview of changes in our understanding of the systematics of living rodents, including species recognition and delimitation, phylogenetics, and classification, with emphasis on the last three decades. Roughly, this corresponds to the DNA sequencing era of rodent systematics, but the field is undergoing a transition into the genomic era. At least 248 species were newly described in the period 2000–2017, including novelties such as the first living member of Diatomyidae and a murid species without molars (Paucidentomys vermidax), thus highlighting the fact that our understanding of rodent diversity is going through an age of discovery. Mito-nuclear discordance (including that resulting from mitochondrial introgression) has been detected in some of the few taxonomic studies that have assessed variation of two or more unlinked loci. As studies incorporate more loci, incomplete lineage sorting and introgression are likely to gain recognition as widespread phenomena in the near future. Molecular phylogenetics has had a major impact in rodent phylogeny and allowed the identification of three major rodent clades, here recognized as suborders: 1) the Hystricomorpha (sometimes referred as the Ctenohystrica) and including two infraorders, Hystricognathi and Ctenodactylomorphi; 2) the Sciuromorpha; and 3) the Supramyomorpha, a new suborder that comprises the infraorders Castorimorphi, Anomalurimorphi, and Myomorphi. In spite of the greater understanding and ensuing stability of rodent phylogeny gained during the last three decades, several major areas of the rodent tree remain unresolved or poorly supported. We expect that the analysis of genomic-scale data will help resolve those areas of the radiation of Rodentia that still remain poorly understood. [ABSTRACT FROM AUTHOR]

The genus Oligoryzomys, distributed from southern South America to southern North America, is the most diverse of the tribe Oryzomyini of sigmodontine rodents. Even when 22 species are currently recognized, species boundaries are unclear for several forms. The species Oligoryzomys destructor is one of the least studied species of the genus and is the one with the largest distribution along the Andes (from southern Colombia to northern Bolivia). The species was described without the selection of a holotype and indication of its type locality. In addition, several taxa are regarded as synonyms of O. destructor. These facts are relevant because previous analysis of DNA sequences has shown that O. destructor represents a species complex. Herein, in addition to test the phylogenetic position of O. destructor within the genus Oligoryzomys, we assess patterns of morphological and molecular variation of O. destructor and its associated nominal forms aimed to assess the boundaries of the species. As part of the study, we selected neotypes for Hesperomys destructor and H. melanostoma. At the light of our results, we recognized O. destructor as a species with two subspecies, O. d. destructor and O. d. spodiurus. Also, we discuss the role of Andean rivers, and their different permeability, as allopatric barriers molding the structure of O. destructor. Here, we analyze patterns of morphological and molecular variation aimed to assess the taxonomic status of the long‐tailed mouse Oligoryzomys destructor and its associated nominal forms. As part of the study, we selected neotypes for Hesperomys destructor and H. melanostoma. We concluded that O. destructor is a species formed by two subspecies, O. d. destructor and O. d. spodiurus. [ABSTRACT FROM AUTHOR]

Several issues regarding the systematics and taxonomy of the Neotropical deer tribe Odocoileini, an assemblage of 18 recognized living species currently allocated into 7 genera, remain unclear. The few available phylogenetic analyses indicate that some genera are not monophyletic and that species richness in the group is underestimated. One genus that presents both problems are the stocky and short-legged dwarf deer, Pudu. As currently understood, it includes 2 species, the Northern pudu, Pudu mephistophiles from Peru, Ecuador, and Colombia; and the Southern pudu, P. puda , from southern Chile and nearby Argentina. Here, by means of qualitative and quantitative morphologic analysis and the assessment of genetic variation, we showed that 2 distinct species are encompassed by the current concept of P. mephistophiles. The typical form distributes north of the Huancabamba Depression from northernmost Peru to the north (Ecuador and Colombia), while the other distributes south of the Huancabamba Depression and is a Peruvian endemic. As no name is available for the last one, we describe and name it here. This is the first living cervid species described in the 21st century and the first from the New World in over 60 years. Additionally, as the Southern Pudu (the type species of Pudu) is not sister to the 2 northern pudu species, we revalidate the genus Pudella to allocate the latter 2 species. [ABSTRACT FROM AUTHOR]

The complex orogenic history and structure of Southern South America, coupled with Pleistocene glacial cycles, have generated paleoclimatic and environmental changes that influenced the spatial distribution and genetic composition of natural populations. Despite the increased number of phylogeographic studies in this region and given the frequent idiosyncratic phylogeographic patterns, there is still the need to focus research especially on species that are currently distributed within a wide range of bioclimatic regimes, and that historically have been subject to contrasting scenarios. Liolaemus tenuis is a widely distributed lizard species inhabiting latitudinally in almost 1000 km through central and southern Chile. Here we describe the geographical patterns of genetic variation and lineage diversification within L. tenuis , and their association with geography and Pleistocene glaciations, using sequences from one mitochondrial and two nuclear genes, and five microsatellite loci, and covering most of the species distributional range. Our results revealed a high diversity both within and among populations, as well as two phylogeographic breaks, which are consistent with two of the larger rivers of central Chile, the Maipo and Biobío Rivers. Liolaemus tenuis is characterized by several allopatric lineages, especially in its north and central range, which suggest a history of multiple vicariance processes. Conversely, populations found in the southern range, south of the Biobío River, show signatures of recent decreases in effective population sizes, coupled with recent range expansions and secondary contact. Niche “envelope” data are consistent with patterns of genetic variation; both suggest a history of discontinuous areas of relatively stable populations throughout all of the distribution of L. tenuis . These data are also consistent with higher probabilities of habitat suitability north of the Maipo River (ca. 33°S), in both coastal areas and the “Intermediate Depression” between 34° and 37°S, as well as in the southern Coastal Cordillera between the Biobío and Araucanía regions. Interestingly, both molecular and niche envelope modeling data suggest that some populations may have persisted in fragmented refugia in Andean valleys, within the limits of the ice sheet. Finally, our results suggest that several populations of L. tenuis colonized glaciated regions from refugial areas in lowlands and coastal regions, and in the southern distribution, historic migration events would have occurred from refugial areas within the limits of the ice sheet. [ABSTRACT FROM AUTHOR]

Two subspecies of Andinomys edax are currently recognized. Andinomys e. edax ranges from southern Perú to northernmost northwestern Argentina and A. e. lineicaudatus is mainly distributed in southern northwestern Argentina. However, some workers have recognized both taxa as distinct species, stating that A. edax is restricted to Puna and Prepuna habitats between 2,000 and 4,800 m elevation, whereas A. lineicaudatus occurs in Yungas forest below 2,500 m. We assessed the taxonomic status of both forms through an integrative approach including morphological (discrete skin and skull characters), morphometric (univariate and multivariate), geographicenvironmental niche modeling (Mahalanobis Typicalities), and molecular (Bayesian analysis of cytochrome-b gene sequences) analyses. We did not find characters that consistently differentiated skins and skulls of the 2 forms. The morphometric analysis indicated that lineicaudatus is, on average, larger than edax for some measurements, but only 2 (alveolar width and occipital condyle width) differed significantly between forms. No group of specimens was clearly segregated in the PCA morphospace. Distribution models obtained separately for each taxon do not offer a better fit to the known distribution than models based on the combined data sets. We documented coincident environmental variables as relevant in the model building of edax and lineicaudatus, noting some segregation in elevation, but similar habitat suitability for the remainder of the environmental variables. The geographic continuity between niche models of edax and lineicaudatus was clear but specimens morphologically assignable to each of the nominal forms were not found in areas of overlap. The phylogenetic analyses recovered a polytomy of 4 allopatric and genetically divergent clades, which also failed to support the taxonomic hypothesis of 2 species. Based on all available evidence, we conclude that Andinomys consists of a single species. Nevertheless, observed genetic divergences among clades and their geographic distribution indicate that past events probably fragmented populations of A. edax. [ABSTRACT FROM AUTHOR]

A previous study showed that Dromiciops gliroides has deep phylogeographic structure, with 3 allopatric and highly differentiated groups. Here, we constructed on that study by assessing the morphologic variation of D. gliroides. Our results show that along its distribution Dromiciops is morphologically highly variable and that the geographic pattern of morphologic variation matches the phylogeographic pattern. Taken together, morphological and molecular data indicate the existence of 2 unrecognized and unnamed species of monito del monte, which are here named and described. Cranial and dental features can easily distinguish species of Dromiciops. One of the new species is endemic of Chile, and the other new species occurs in Argentina and Chile. D. gliroides s.s. is restricted to the southern part of the genus distribution including Chiloé Island. We comment on the conservation significance of our findings and on the need of continuing with field- and collection-based research in order to characterize the richness of the Chilean mammal assemblage. [ABSTRACT FROM AUTHOR]

Affiliation with a scientific area or degree program could affect one´s religious beliefs and acceptance of evolution; however, this issue has been poorly studied. Moreover, little information is available regarding Chilean university scientists' views on religion and evolution. This study aims to provide the first documentation of the opinion of scientists at a Chilean University with regard to religion and evolution. This was done by conducting a personal survey of first and last year undergraduate students, graduate students, and faculty. We found that nonreligiosity, as well as acceptance of Darwinian evolution, increased with possession of an advanced degree and this correlation was stronger for individuals who study biology and physics in comparison to those who study chemistry. Although less than 30 percent of undergraduate students are atheists/agnostics, more than 70 percent of faculty members are atheist or agnostic. However, most of the surveyed scientists did not see a conflict between science and religion. [ABSTRACT FROM AUTHOR]

The mygalomorph genus Grammostola (family Theraphosidae) is endemic to South America. The species Grammostola anthracina is one of the largest spiders in Uruguay and reputed to be the longest lived tarantula in the world. This nominal species has two distinct colour morphs comprising black and reddish-brown forms with controversial taxonomic status. Here, we present a phylogenetic study based on molecular characters (cytochrome c oxidase subunit I) of haplotypes of G. anthracina and closely related species. Our analysis together with new morphological data and biogeographical information indicates that the two morphs of G. anthracina constitute different species that are not sister to each other. Consequently, a new species, Grammostola quirogai is described, diagnosed and illustrated to encompass the black morph. Phylogenetic relationships and new taxonomic characters for Grammostola species included in this study are discussed. [ABSTRACT FROM AUTHOR]

We report an elevational record for the Andean sigmodontine Puna Mouse Punomys , which is also the first record of the genus in Chile. The record is based on a mummified specimen that we discovered at an elevation of 5,461 m (17,917 feet) in the caldera of Volcán Acamarachi, Región de Antofagasta, Chile. Results of a morphological assessment suggest that the specimen can be provisionally referred to the species P. lemminus. This new record also extends the known geographic distribution of the genus by 700 km to the south and brings the known Chilean mammal richness to a total of 170 living species and 88 genera. This finding highlights the need for increased survey efforts in more remote, high-elevation regions and demonstrates that there is still much to be learned about the mammal fauna of the Andean Altiplano. [ABSTRACT FROM AUTHOR]

We present a comprehensive systematic study of Holochilus, a sigmodontine genus of large, herbivorous, and semiaquatic rodents widely distributed in South America. Remarkably, given its complex taxonomic history and large economic as well as epidemiological importance, the alpha taxonomy of Holochilus has not benefited from a molecular-based approach. The study is based on sequences of 1 mitochondrial and 3 nuclear loci that were analyzed by maximum likelihood and Bayesian inference. Analyses include sequences of specimens from localities from Argentina, Bolivia, Brazil, Colombia, Paraguay, Peru, Suriname, and Uruguay, representing all but 2 of the species currently recognized in the genus. Of the 4 data matrices, the mitochondrial data set contains the largest geographic coverage and recovered 6 species-level lineages that form 2 well-supported species groups: the brasiliensis species group formed by H. brasiliensis and H. vulpinus and the sciureus species group composed by H. chacarius, H. sciureus, and 2 currently unnamed forms. Surprisingly, in the cytochrome b gene analyses, the 2 species groups are not sister to each other; i.e., Holochilus is not monophyletic, although these topologies lack significant support. However, the monophyly of Holochilus was supported by the 3 nuclear loci as well as by the combined analysis of all 4 loci. These genealogical results are the basis of taxonomic and biogeographic considerations. Presentamos un estudio sistemático comprensivo sobre Holochilus, un género sigmodontino de grandes roedores herbívoros y semi-acuáticos ampliamente distribuido en América del Sur. Llamativamente, dada su compleja historia taxonómica y el gran impacto económico y epidemiológico, la taxonomía alfa de Holochilus no se ha beneficiado de un abordaje basado en evidencia molecular. El estudio se basa en secuencias de 1 gen mitocondrial y de 3 nucleares que fueron analizadas con máxima verosimilitud e inferencia Bayesiana. Los análisis incluyen secuencias de especímenes colectados en localidades de Argentina, Bolivia, Brasil, Colombia, Paraguay, Perú, Surinam y Uruguay, representando todas, con excepción de 2, las especies actualmente reconocidas en el género. La genealogía mitocondrial, que es la que tiene la mayor cobertura geográfica de Holochilus, recobra 6 linajes de nivel de especie que forman 2 grupos de especies bien apoyados: el grupo de especies brasiliensis integrado por H. brasiliensis y H. vulpinus y el grupo de especies sciureus que está compuesto por H. chacarius, H. sciureus y 2 formas aparentemente sin nominar. Llamativamente, en los análisis basados en el gen mitocondrial los 2 grupos de especies no son hermanos; i.e., Holochilus no es monofilético, aunque esta topología no tiene apoyo significativo. Sin embargo la monofilia de Holochilus es apoyada por los análisis de los 3 genes nucleares y por el análisis combinado de los 4 genes. Estos resultados genealógicos son la base de consideraciones taxonómicas y biogeográficas. [ABSTRACT FROM AUTHOR]

Background: Much debate has focused on how transitions in life history have influenced the proliferation of some clades. Rodents of the subfamily Sigmodontinae (family Cricetidae) comprise one of the most diverse clades of Neotropical mammals (~400 living species in 86 genera). These rodents occupy a wide range of habitats and lifestyles so that ecological context seems relevant to understand the evolution of this group. Several changes in the landscape of South America through the Neogene might have provided vast resources and opportunity to diversify. The aim of this study was to examine whether transitions between i) lowland and montane habitats, ii) open vegetation and forest, and iii) distinct molar architectures are correlated with shifts in diversification rates and to characterize the general pattern of diversification. Results: Based on a dense taxon sampling of 269 species, we recovered a new phylogeny of Sigmodontinae that is topologically consistent with those of previous studies. It indicates that the subfamily and its major lineages appeared during the Late Miocene. Analyses suggest that vegetation type and elevational range are correlated with diversification rates, but not molar architecture. Tropical lowlands accumulated more lineage diversity than other areas and also supported high speciation rates. Across the radiation the subfamily Sigmodontinae appear to have experienced a decline in diversification rate through time. We detected mixed evidence for lineage-specific diversification rate shifts (e.g., leading to the clades of Akodon, Bibimys, Calomys and Thomasomys). Conclusion: We report that the evolution of habitat preference (considering vegetation type and elevational range) was associated with diversification rates among sigmodontine rodents. We propose that the observed diversification slowdown might be the result of ecological or geographical constraints. Our results also highlight the influence of the tropical lowlands -which might have acted as both "a cradle and a museum of species." The tropical lowlands accumulated greater diversity than the remainder of the group's range. [ABSTRACT FROM AUTHOR]

Analyses of morphological and molecular data indicate the existence of an unrecognized and unnamed species of soft-haired mouse, genus Abrothrix. Here, we name and describe this new species, which inhabits the Valdivian ecoregion, from the north of Chiloé Island onto the mainland in the Chilean regions of Los Lagos and Los Ríos; it also occurs at a single locality in the Argentinean province of Neuquén. Long confused with A. sanborni, the new species presents a unique combination of characters that differentiate it in external, cranial, phallic, and dental terms from its congeners. Phylogenetic analysis, based on cytochrome-b gene sequences, indicates that the new species is sister to a clade formed by the austral species A. lanosa and A. sanborni and differs on average from them by 5.7% and 5.2%, respectively. Results based on the nuclear Fgb-I7 locus are less conclusive regarding the phylogenetic position of the new species but also show its distinction. We comment on the conservation significance of our findings, considering that forests of the Valdivian ecoregion are suffering substantial human disturbance through intensive logging. [ABSTRACT FROM AUTHOR]

Even though Paraguay has had a long history of Mammalogy, since 2007, several new rodent, bat, marsupial, and armadillo species have been added to the list of known species for the country. Herein, we add two new species of marsupials to the fauna of Paraguay, Philander opossum and Cryptonanus unduaviensis. These records improve the understanding of both species in South America. The Paraguayan records of P. opossum, corresponding to the subspecies Philander opossum canus, fill in a major gap in its known distribution between Bolivia and Argentina, while the record of C. unduaviensis accounts for an extension of at least 290 km toward the southeast and is the first record reported outside of Bolivia. These two new species increase the known Paraguayan marsupial fauna to 18 species. [ABSTRACT FROM AUTHOR]

Background: Much debate has focused on how transitions in life history have influenced the proliferation of some clades. Rodents of the subfamily Sigmodontinae (family Cricetidae) comprise one of the most diverse clades of Neotropical mammals (~400 living species in 86 genera). These rodents occupy a wide range of habitats and lifestyles so that ecological context seems relevant to understand the evolution of this group. Several changes in the landscape of South America through the Neogene might have provided vast resources and opportunity to diversify. The aim of this study was to examine whether transitions between i) lowland and montane habitats, ii) open vegetation and forest, and iii) distinct molar architectures are correlated with shifts in diversification rates and to characterize the general pattern of diversification. Results: Based on a dense taxon sampling of 269 species, we recovered a new phylogeny of Sigmodontinae that is topologically consistent with those of previous studies. It indicates that the subfamily and its major lineages appeared during the Late Miocene. Analyses suggest that vegetation type and elevational range are correlated with diversification rates, but not molar architecture. Tropical lowlands accumulated more lineage diversity than other areas and also supported high speciation rates. Across the radiation the subfamily Sigmodontinae appear to have experienced a decline in diversification rate through time. We detected mixed evidence for lineage-specific diversification rate shifts (e.g., leading to the clades of Akodon, Bibimys, Calomys and Thomasomys). Conclusion: We report that the evolution of habitat preference (considering vegetation type and elevational range) was associated with diversification rates among sigmodontine rodents. We propose that the observed diversification slowdown might be the result of ecological or geographical constraints. Our results also highlight the influence of the tropical lowlands -which might have acted as both “a cradle and a museum of species.” The tropical lowlands accumulated greater diversity than the remainder of the group's range. [ABSTRACT FROM AUTHOR]

Based on 2 collected specimens of the rodent Phaenomys ferrugineus (Thomas), an endemic species of the Atlantic Forest, novelty information about its anatomy is provided as well as the results of the first phylogenetic analysis based on DNA sequences including this genus. This sigmodontine is characterized by a skull with marked supraorbitary crests, a well developed basicranial region, a primitive circulatory carotid pattern, the presence of a tegmen tympani, the absence of alisphenoid strut, and a mandible showing an important development of the region where the internal pterigoid muscle inserts. Phaenomys has 12 ribs, an unilocular-hemiglandular stomach, lacks gall bladder and has a large blind gut. A phylogeny based on the combined analysis of 2 molecular markers retrieves Phaenomys as sister to the genus Wiedomys. The plausible existence of a clade including endemic genera of the southeastern portion of the subcontinent, is discussed. [ABSTRACT FROM AUTHOR]

Sooretamys is a monotypic genus of the family Cricetidae, subfamily Sigmodontinae, that is distributed throughout eastern South America in the Atlantic Forest Biome, including Argentina, Brazil, and Paraguay. The taxonomic history of the forms associated with this genus is long and relatively complex, and few studies have evaluated the taxonomic problems of this genus. To this end, our goal was to describe the degree and geographical pattern of morphological and molecular variation in this genus to test the current hypothesis that the genus is monotypic, and, as a consequence, to determine the status of the nominal forms associated with Sooretamys. Accordingly, we employed morphometric, morphological, and molecular tools, according to an integrative taxonomy approach. The results show that some level of morphometric discontinuity is present between the individuals from Paraguay and those from adjacent localities in Brazil and Argentina; sharp discontinuities were not observed in qualitative traits. Molecular analyses of the mitochondrial cytochrome b gene showed that the Paraguayan populations have some degree of genetic differentiation, but the haplotypic variants do not form a monophyletic group. Thus, the evidence so far suggests a difference in the genes and morphology of the Paraguayan population, but there is no consistent resolution (e.g. lack of monophyly) to show that specimens from Paraguay represent a distinct population that would merit taxonomic recognition. Thus, we recognize a single species within the genus Sooretamys, named Sooretamys angouya. The pattern of morphological and genetic differentiation of Sooretamys could be the result of divergence with gene flow. However, our data also correspond in some aspects with the model advanced by Carnaval & Moritz, which claims the existence of stable Atlantic Forest areas where the forest biota persisted during the Quaternary climatic fluctuations. Whatever process has occurred, S. angouya represents one species with a complex evolutionary history, and the analysis of additional samples would be welcome to further elucidate the process of diversification of this taxon. © 2014 The Linnean Society of London [ABSTRACT FROM AUTHOR]

Akodontini is the 2nd most diverse tribe of Sigmodontinae, which in turn is one of the most speciose groups of muroid rodents. This tribe is among the most poorly understood Neotropical taxa, with most taxonomic problems concentrated in Andean species, especially those inhabiting the northern Andes. Here, applying morphological, morphometric, and phylogenetic analyses (based on 1 mitochondrial and 1 nuclear gene), we review the systematic and taxonomic status of the Bogotá akodont, Akodon bogotensis Thomas, 1895, and the Ecuadorean akodont, A. latebricola (Anthony, 1924) (Cricetidae: Sigmodontinae). Morphometric and morphological analyses give evidence of the morphological distinctiveness of A. latebricola and A. bogotensis. Specifically, these small-sized species present a unique combination of characters that includes soft, grizzled to dark chestnut dorsal fur; dark brown manus, pes, and tail; slender and proportionally long rostra; indistinct zygomatic notches; narrow, backward-sloping zygomatic plates; wedge-shaped infraorbital foramina; proportionally short incisive foramina; inflated braincase and auditory bullae; and opposite molar cusps. In agreement with these morphological results, phylogenetic analyses placed latebricola outside the tribe Akodontini. Based on these results, we propose and describe a new genus for latebricola and bogotensis. [ABSTRACT FROM AUTHOR]

According to the Carnaval--Moritz (CM) model of Pleistocene refugia, during the Last Glacial Maximum, forested areas of the Atlantic Forest (AF) were restricted to isolated refugia and later expanded to their current distribution. Phylogeographic patterns of several vertebrate species corroborated the existence of the so-called Pernambuco, Bahia, and São Paulo refugia in the central and northern AF. Here we shift focus to the neglected southern and interior AF by addressing the phylogeography of the mouse Akodon montensis as inferred through analysis of cytochrome-b gene sequences of 86 specimens collected at 36 localities in Argentina, Brazil, and Paraguay. Three main clades were recovered with average genetic divergence of 2.5%: a northern clade, differentiated in the Bahia refuge, a southern clade--for which we propose the Rio Grande do Sul refugium--and a central clade (widely extending from coastal Brazil to Argentina and Paraguay). Within the latter, genetic diversity and historical demographic estimations support differentiation in the São Paulo refugium and their later population expansion toward interior AF. Additionally, no riverine barrier effect was found associated with the main river in the interior AF, the Paraná River. Taken as a whole, the phylogeographic pattern of A. montensis and its recent population history are mainly concordant with the CM model. [ABSTRACT FROM AUTHOR]

Historical climate changes and orogenesis are two important factors that have shaped intraspecific biodiversity patterns worldwide. Although southern South America has experienced such complex events, there is a paucity of studies examining the effects on intraspecific diversification in this part of the world. Liolaemus pictus is the southernmost distributed lizard in the Chilean temperate forest, whose genetic structure has likely been influenced by Pleistocene glaciations. We conducted a phylogeographic study of L. pictus in Chile and Argentina based on one mitochondrial and two nuclear genes recovering two strongly divergent groups, Northern and Southern clades. The first group is distributed from the northernmost limit of the species to the Araucanía region while the second group is distributed throughout the Andes and the Chiloé archipelago in Southern Chile. Our results suggest that L. pictus originated 751 Kya, with divergence between the two clades occurring in the late Pleistocene. Demographic reconstructions for the Northern and Southern clades indicate a decrease in effective population sizes likely associated with Pleistocene glaciations. Surprisingly, patterns of genetic variation, clades age and historical gene flow in populations distributed within the limits of the Last Glacial Maximum (LGM) are not explained by recent colonization. We propose an "intra-Andean multiple refuge" hypothesis, along with the classical refuge hypothesis previously proposed for the biota of the Chilean Coastal range and Eastern Andean Cordillera. Our hypothesis is supported by niche modelling analysis suggesting the persistence of fragments of suitable habitat for the species within the limits of the LGM ice shield. This type of refuge hypothesis is proposed for the first time for an ectothermic species. [ABSTRACT FROM AUTHOR]

Abstract: The subgenus Marmosa (Micoureus) Lesson, 1842 includes six species of long-tailed, black masked mouse-opossums widely distributed in forested areas of the Neotropics from northern Argentina to Belize. Most of the nominal forms of Marmosa (Micoureus) have not been revised since 1933 and some currently accepted synonymies are in need of revision; similarly distributions of these forms remain for the most part unclear. Herein, we report Paraguayan new and noteworthy locality records for Marmosa (Micoureus), including the first records for the western Dry Chaco region. Specimens were identified to the species level on the basis of morphological and molecular data. In addition, we conducted a phylogenetic analysis that includes sequences of five of the six species currently recognized of Micoureus incorporating a total of 70 sequences of the subgenus. This constitute the most taxonomically and geographically dense phylogenetic analysis of Micoureus. Results show that the most basal dichotomy of the Micoureus clade does not delimit cis- and trans-Andean reciprocally monophyletic groups, rending the cis group paraphyletic to the single trans-species included, suggesting that the colonization of the western (trans) side of the Andes was a relatively late event in the biogeographic history of Micoureus. In addition, the phylogenetic analysis shows that additional taxonomic work is much needed to clarify the number of distinct biological units, either species or subspecies, within Micoureus. [Copyright &y& Elsevier]

Until now, there has been a single Paraguayan record of climbing rats of the genus Rhipidomys (Tschudi, 1845), and the specimen has not been identified at the species level. Remarkably, this record has been overlooked in recent mammal lists. Field work conducted in Paraguay during and since 2006 has produced the second and third records of Rhipidomys for this country. We conducted an assessment of external and skull morphologic variation, as well as Maximum Parsimony and Bayesian analyses based on DNA sequences, all of which indicate that all three known Paraguayan specimens of Rhipidomys belong to the species Rhipidomys macrurus (Gervais, 1855). In addition, we provide information distinguishing R. macrurus from some of its congeners, as well as new natural history data. There is now a total of 31 sigmodontine species with published Paraguayan records. [ABSTRACT FROM AUTHOR]

We present the most comprehensive study to date of species groups in Ctenomys (tuco-tucos), a species-rich genus of Neotropical rodents. To explore phylogenetic relationships among 38 species and 12 undescribed forms we sequenced the complete mitochondrial cytochrome-b genes of 34 specimens and incorporated 50 previously published sequences. Parsimony, likelihood, and Bayesian phylogenetic analyses were performed using additional hystricognath rodents as outgroup taxa. The basal dichotomy of Ctenomys splits C. sociabilis from the remaining tuco-tucos, within which 8 main species groups were identified: boliviensis, frater, mendocinus, opimus, magellanicus, talarum, torquatus, and tucumanus. Whereas most of these groups refer to previous clades proposed on the basis of chromosomes or morphology, the torquatus and magellanicus species groups are novel taxonomic hypotheses. However, relationships among species groups are poorly resolved. Furthmore, the positions of C. leucodon, C. maulinus, and C. tuconax are conflicting or unresolved, and they might represent additional independent lineages. On the basis of molecular dating, we estimate that most species groups originated approximately 3 million years ago. [ABSTRACT FROM AUTHOR]

Abstract: The genus Ctenomys of subterranean rodents is one of the most diverse of the mammal radiation. In addition to external and skull morphology, studies of Ctenomys alpha taxonomy have relied in an intense manner on chromosomal variation and several populations of this genus have been characterized only by means of cytogenetic techniques. Ctenomys pearsoni is the most karyotypically variable species of the genus (2n=56-70). The goal of this study was to assess the pattern of geographic variation of the skull morphology in several karyomorphs of Ctenomys pearsoni. Our main results indicate that, with the exception of the Solís karyomorph, the remaining are morphologically indistinguishable. These results also agree with previous morphological and population genetics analyses performed in this species. Taken together the available evidence, we support the point of view that not all fixations of chromosomal rearrangement define independent evolutionary units. [Copyright &y& Elsevier]

Loxodontomys micropus is a rodent that is widely distributed in Andean and Patagonian Argentina and Chile. This range covers a heterogeneous area that has been influenced by geologic and palaeoclimatic events, such as the glaciations during the Neogene. To investigate the genetic structure, phylogeographic pattern, and biogeographic history of this sigmodontine rodent we analyzed a 801-base-pair fragment of the mitochondrial genome (cytochrome-b gene) of 87 specimens from 24 localities from Argentina and Chile. Results indicate that L. micropus has a shallow genealogy that is geographically structured and is a taxon characterized by an historical population expansion. We discuss the distribution of the genetic variation of L. micropus in relation to population history and the concordance with other codistributed sigmodontine rodents. On the basis of molecular evidence, we suggest that the L. pikumche, corresponding to the second extant species of the genus, could be a junior synonym of L. micropus. [ABSTRACT FROM AUTHOR]

Species are impacted by climate change at both ecological and evolutionary time scales. Studies in northern continents have provided abundant evidence of dramatic shifts in distributions of species subsequent to the last glacial maximum (LGM), particularly at high latitudes. However, little is known about the history of southern continents, especially at high latitudes. South America is the only continent, other than Antarctica, that extends beyond 40 °S. Genetic studies of a few Patagonian species have provided seemingly conflicting results, indicating either postglacial colonization from restricted glacial refugia or persistence through glacial cycles and in situ differentiation. Using mitochondrial DNA sequences of 14 species of sigmodontine rodents, a major faunal ensemble of Patagonia and Tierra del Fuego, we show that at least nine of these species bear genetic footprints of demographic expansion from single restricted sources. However, timing of demographic expansion precedes the LGM in most of these species. Four species are fragmented phylogeographically within the region. Our results indicate that (i) demographic instability in response to historical climate change has been widespread in the Patagonian-Fueguian region, and is generally more pronounced at high latitudes in both southern and northern continents; (ii) colonization from lower latitudes is an important component of current Patagonian-Fueguian diversity; but (iii) in situ differentiation has also contributed to species diversity. [ABSTRACT FROM AUTHOR]

Abstract: Abrothrix lanosus (Thomas, 1897) is morphologically redescribed on the basis of new specimens collected in Tierra del Fuego (Argentina). Cranial, mandibular, skeletal, penile, and chromosomal characteristics are described and compared with other species of Abrothrix, especially those of the Patagonian-Fueguian region. Its phylogenetic position within Abrotrichini is explored using DNA sequences of the mitochondrial cytochrome b (cyt b) and the nuclear Interphotoreceptor Retinoid Binding Protein (IRBP) genes. Phylogenetically, cyt b places A. lanosus as sister of A. jelskii, whereas IRBP groups A. lanosus and A. longipilis. The latter topology is most consistent with morphological data and taxonomic history. Several cranial and mandibular characters distinguish A. lanosus from the other species of the genus, including A. longipilis, which is its most similar species. A. lanosus shares with other congeners a 2n=52 karyotype and differs from other species of Abrothrix by at least 10% (p-distances) sequence divergence in cyt b. In conclusion, A. lanosus is a valid species, readily distinguishable from other Abrothrix in the southern Patagonian-Fueguian region. Although many data, including penile and skull morphology, suggest that A. longipilis is its closest living relative, A. jelskii is retained as a viable alternative until additional data are obtained. [Copyright &y& Elsevier]

We present the most comprehensive systematic study to date of Necromys, a rodent genus distributed in open areas north and south of Amazonia and in Andean grasslands. The study is based on sequences of the cytochrome-b gene that were analyzed by parsimony and Bayesian approaches. The analyses include sequences of 62 specimens from 51 localities from Argentina, Bolivia, Brazil, Colombia, Paraguay, Peru, Uruguay, and Venezuela, representing all but 1 of the species currently recognized in the genus. Necromys was recovered as a monophyletic group and we found a large polytomy at its base that involves 3 lineages. One, represented by the Andean N. lactens, shows a marked phylogeographic pattern. The 2nd clade is formed by N. urichi from the northern grasslands of South America and N. amoenus from the central Andes. Results suggest that each of these taxa may represent more than 1 biological species. The 3rd clade is formed by lowland species found south of Amazonia. Within this clade N. obscurus is sister to the remaining species. Haplotypes recovered from specimens assigned to N. benefactus, N. temchuki, and N. lasiurus form a clade, but these taxa do not form reciprocally monophyletic groups, nor does this large clade possess geographic structure. These genealogical results, discussed in the context of genetic variation, are the basis of taxonomic (e.g., N. benefactus and N. temchuki are regarded as junior synonyms of N. lasiurus) and biogeographic considerations. [ABSTRACT FROM AUTHOR]

Integrated analyses of morphological, chromosomal, and molecular data resulted in the description of a new species of the genus Akodon, endemic to the Northern Campos in southern Misiones, Argentina. The new species presents a unique combination of characters, including a narrow zygomatic plate almost without a free upper border, short rostrum, short tail (40% of the head-body length), small and flat auditory bullae, diploid complement of 2n = 36, and several molecular synapomorphies. Phylogenetic analysis, based on cytochrome-b gene sequences, indicates that the Brazilian species Akodon lindberghi is sister to the new species, although this relationship is weakly supported. We comment on the conservation significance of our study, considering that these perisylvan grasslands are suffering substantial human disturbance by agriculture and burning practices. [ABSTRACT FROM AUTHOR]

We present a systematic study of Scapteromys populations from Argentina, Paraguay, and Uruguay, based on molecular and morphological evidence. First, based on DNA sequences (801 base pairs) from the mitochondrial cytochrome-b gene, we found that Scapteromys populations fall into 2 main clades; I formed by Argentinean and Paraguayan populations together with 1 population from western Uruguay, and the other constituted by the remaining Uruguayan populations. Analysis of molecular variance showed that 86.93% of the genetic variation uncovered in Scapteromys is explained by differences between clades. Morphological analyses corroborated the existence of 2 main morphotypes among Scapteromys specimens. The phylogeographic break identified is mostly congruent with patterns of morphological and chromosomic variation. In light of these results, we propose that S. aquaticus be elevated to the rank of species, we redefine the known distributions of S. aquaticus and S. tumidus, and we provide a list of character states that allow an unambiguously diagnosis of both species. [ABSTRACT FROM AUTHOR]

This is the first cladistic analysis of sigmodontine rodents (Cricetidae, Sigmodontinae) based on nuclear and mitochondrial DNA sequences. Two most parsimonious cladograms (7410 steps in length; CI=0.199; RI=0.523) were discovered. Sigmodontinae appears well supported. Sigmodon is sister to the remaining living sigmodontines. It is shown that Euneomys is not a phyllotine and that the Reithrodon group is not monophyletic. Results corroborate that the abrothricines form a natural group that is not part of the akodont radiation. The akodontine tribe is well supported, and is composed of five main clades, whose limits and relationships are thoroughly discussed. For instance, the scapteromyines do not form a natural group and they fall within the akodontine clade. Additionally, I present some taxonomic judgments and comments on the historical biogeography of sigmodontines in the light of the newly discovered relationships. For example, five akodontine divisions are suggested: the Akodon, the Bibimys, the Blarinomys, the Oxymycterus, and the Scapteromys Divisions. It is shown that traditional hypotheses of sigmodontine historical biogeography are falsified by the recovered topology. [Copyright &y& Elsevier]

Abrotrichini is the sigmodontine tribe with the fewest species in Peru, known only from two species: Abrothrix andina and Ab. jelskii, both distributed in the high Andean regions of Peru above 3000 m in altitude. A detailed review of the morphology of historical specimens collected in the Tacna department and identified as Akodon mollis was conducted. As a result, we found that the examined specimens corresponded to Abrothrix olivacea, a species previously known only from Chile and Argentina. This discovery represents the first record of this species in Peru, extending its distribution range 165 km north of its previous northernmost record in Quebrada Camarones, Arica-Parinacota, Chile. Furthermore, this finding significantly reduces the distribution range of Akodon mollis to the northwestern region of Peru. We also provide key craniodental characters to differentiate species of Abrothrix and Akodon in southwestern Peru and northern Chile. For Peru, this record increases the diversity of mammals to 588 species and rodents to 201 species. In the case of the Tacna department, mammalian diversity increases to 47 species. This work highlights the value of natural history museum collections in enhancing our understanding of species diversity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Current taxonomy does not reflect the real species richness of the genus Octodon. • Depending on the analysis between 7 and 11 species of degus are delimited. • Some of the previously unrecognized species are morphologically distinct. • Some of the previously unrecognized species are morphologically indistinct. As currently understood, the genus Octodon contains five species degus , lunatus , bridgesii , pacificus , and ricardojeda. Previous phylogenetic studies suggest that genus specific diversity is underestimated. In order to evaluate the taxonomic diversity of Octodon , we implemented unilocus (cytochrome-b) and multilocus (cytochrome-b + 4 nuclear genes) species delimitation methods. Octodon degus was recovered as a sister of the other species of the genus. The unilocus bGMYC and mPTP methods, based on cytochrome-b sequences, delimits 11 and 7 candidate species respectively, and both methods fail to recognize O. pacificus from O. ricardojeda. Results of the multilocus analysis (BPP) vary as a function of the dataset used. When the five genes are used 11 species are delimited, while eight species are delimited when only the nuclear genes are used. Octodon bridgesii is shown as comprising at least two species (one on the Pacific coast and the typical form found on the Andean slopes), while O. ricardojeda may comprise two species (one on the Chilean side of the Andes and the other in Argentina). Likewise, both multilocus matrices recover O. pacificus as a distinct species. This shows that species diversity of Octodon is underestimated. Remarkably, many of the delimited species based on genetic data are morphologically differentiated in cranio-dental characteristics. However, a pair of species has not achieved morphological differentiation, being cryptic species. Finally, the incongruence between mitochondrial and nuclear phylogenies suggests that processes such as incomplete lineage sorting and/or introgression have been present during the radiation of the genus. [ABSTRACT FROM AUTHOR]