Taxonomic review of genusSooretamys Weksler, Percequillo & Voss (Rodentia: Cricetidae: Sigmodontinae): an integrative approach

Uncovering species boundaries through qualitative and quantitative morphology in the genus Dasyprocta (Rodentia, Caviomorpha), with emphasis in D. punctata and D. variegata

The genus Dasyprocta Illiger, 1811 includes at least 13 species of medium-sized caviomorph rodents, widely distributed from Mexico to northern Argentina. Despite being abundant, largely diurnal, and easily identifiable by their external traits, the taxonomy of this genus remains poorly understood. In this work, we reviewed the taxonomy of Dasyprocta along the Andes and adjoining lowland areas of the western Neotropics, including samples from Mexico to northern Argentina, with emphasis on two species largely confounded—sometimes considered as synonyms—during the last century: D. punctata Gray, 1842 and D. variegata Tschudi, 1845. In the construction of our taxonomic hypotheses, we use a purely morphological approach, emphasizing qualitative and quantitative cranial features and external traits (color patterns). The results of multivariate statistical analysis and differences in color patterns support the species-level validity of D. punctata and D. variegata. Within this latter nominal form, we also include those populations from northern Argentina and eastern Bolivia that recently were referred to D. azarae. Based on our results, D. punctata (including bellula, callida, candelensis, chiapensis, chocoensis, colombiana, dariensis, isthmica, nuchalis, richmondi, underwoodi, yucatanica, and zuliae) extends from southern Mexico to Colombia, Ecuador, northernmost Peru, and western Venezuela, while D. variegata (including azarae, boliviae, and yungarum) is distributed from south–central Peru and southwestern Brazil to Bolivia and northwestern Argentina.

A new species of Akodon Meyen, 1833 (Rodentia: Cricetidae: Sigmodontinae) endemic from the Brazilian Cerrado

Akodon is the second most diverse genus of sigmodontine rodents, comprising 40 extant species. Widely distributed through different environments of South America, the genus ranges from forested to open-vegetation areas, from semiarid to mesic regions, and from Andean altitudes to the lowlands of eastern Brazil. In Brazil, most species are from the Atlantic Forest, inhabiting lowland and montane habitats, with a few taxa also present in areas transitional with the Cerrado and Pantanal. Based on an integrative approach of genetics (cytogenetic and molecular data) and morphology (qualitative and quantitative external and craniodental data), we present in this contribution the hypothesis of a new species of Akodon based on specimens collected in the southwestern limit of the Cerrado domain, in the seasonally dry forests of the Serra da Bodoquena, Mato Grosso do Sul, Brazil. The new species was recovered as a distinct lineage sister to Akodon philipmyersi, a poorly known species from the Northern Campos grasslands of Misiones Province, Argentina, and can be distinguished from its congeners by its karyotype (2n = 40, FN = 40), morphology (morphometric, pelage, and skull characters), as well as by its degree of genetic divergence (above 7.5% in Cytb sequences). This new species is endemic to the Cerrado, one of the world’s biodiversity hotspots, and to Serra da Bodoquena, one of the top priority areas for conservation in Brazil. Moreover, the new species increases the number of lineages of Akodon in Brazil, emphasizing the richness and endemism currently found in the Cerrado domain, and the importance of the open formations to the diversification of Neotropical taxa.

Tempo and mode of evolution of oryzomyine rodents (Rodentia, Cricetidae, Sigmodontinae): A phylogenomic approach

The tribe Oryzomyini is an impressive group of rodents, comprising 30 extant genera and an estimated 147 species. Recent remarkable advances in the understanding of the diversity, taxonomy and systematics of the tribe have mostly derived from analyses of single or few genetic markers. However, the evolutionary history and biogeography of Oryzomyini, its origin and diversification across the Neotropics, remain unrevealed. Here we use a multi-locus dataset (over 400 loci) obtained through anchored phylogenomics to provide a genome-wide phylogenetic hypothesis for Oryzomyini and to investigate the tempo and mode of its evolution. Species tree and supermatrix analyses produced topologies with strong support for most branches, with all genera confirmed as monophyletic, a result that previous studies failed to obtain. Our analyses also corroborated the monophyly and phylogenetic relationship of three main clades of Oryzomyini (B, C and D). The origin of the tribe is estimated to be in the Miocene (8.93-5.38 million years ago). The cladogenetic events leading to the four main clades occurred during the late Miocene and early Pliocene and most speciation events in the Pleistocene. Geographic range estimates suggested an east of Andes origin for the ancestor of oryzomyines, most likely in the Boreal Brazilian region, which includes the north bank of Rio Amazonas and the Guiana Shield. Oryzomyini rodents are an autochthonous South America radiation, that colonized areas and dominions of this continent mainly by dispersal events. The evolutionary history of the tribe is deeply associated with the Andean cordillera and the landscape history of Amazon basin.

A new living species of degu, genus Octodon (Hystricomorpha: Octodontidae)

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.

Genetic and morphological variation of Oxymycterus (Rodentia: Sigmodontinae) in the Brazilian Atlantic Forest

We present a new assessment of the genetic and morphological variation within Oxymycterus quaestor Thomas, 1903, which currently includes the junior synonyms O. judex Thomas, 1909 and O. misionalis Sanborn, 1931. We integrate distinct lines of evidence, including variation of mitochondrial (Cytochrome b [Cytb]) and nuclear (intron 7 of beta fibrinogen gene [Fgb]) sequences, and the assessment of skull quantitative traits based on geometric morphometrics, throughout the Atlantic Forest of Southeastern-Southern Brazil, Argentina, and Paraguay. Phylogenetic relationships based on Cytb indicate that O. quaestor is structured in four well-supported clades (lineages A–D), one of them (lineage C) including topotypes of a previously associated nominal form (O. judex). However, these Cytb lineages exhibit lower levels of differentiation based on the Fgb locus, and are not recovered in the genealogies of this nuclear marker, representing a case of mitonuclear discordance. The Cytb lineages also broadly overlapped in the morphospace both in skull shape and size, which sustain the current wider concept of O. quaestor as one single young species (0.947 Myr) that is recently expanding, and ultimately branching out, in the Atlantic Forest.

Taxonomic revision of the pampas cat Leopardus colocola complex (Carnivora: Felidae): an integrative approach

The pampas cat Leopardus colocola has been subject to conflicting classifications over the years. Currently, one polytypic species with seven subspecies is recognized, but integrative taxonomic study for this debated group has never been done. Here, we combine the broadest morphological coverage of the pampas cat to date with molecular data and ecological niche models to clarify its species composition and test the validity of recently proposed subspecies. The multiple lines of evidence derived from morphology, molecular, biogeography and climatic niche datasets converged on the recognition of five monotypic species: L. braccatus, L. colocola, L. garleppi (including thomasi, budini, steinbachi, crespoi and wolffsohni as synonyms), L. munoai and L. pajeros (including crucina as synonym). These five species are morphologically diagnosable based on skin and skull traits, have evolved in distinct climatic niche spaces and were recovered in molecular species delimitation. Contrary to previous taxonomic arrangements, we do not recognize subspecies in pampas cats. To objectively define the two most controversial species, we designate neotypes for L. colocola and L. pajeros. The diversification of pampas cats is associated with Middle Pleistocene glaciations, but additional genetic samples from the central Andean region are still needed to conclusively reconstruct its evolutionary history.

Discovery of a new genus record for Paraguay, the Atlantic Forest endemic rodent Abrawayaomys (Cricetidae, Sigmodontinae)

The mammals of Paraguay are still poorly known. We report a new genus for the country, Abrawayaomys, a spiny cricetid rodent endemic for the Interior Atlantic Forest. This record extends the distribution of the genus approximately 100 km, and west of the Paraná River. This addition increases the number of mammals in Paraguay to 184 and verifies that rodents are the most diverse group of mammals in the country. We outline identifying morphological characters of Abrawayaomys and elaborate on the significance of this finding for conservation and biogeography in the region.

A new species of arboreal rat, genus Oecomys (Rodentia, Cricetidae) from Chaco

A new species of rodent is added to the highly diverse genus Oecomys (Cricetidae, Sigmodontinae, Oryzomyini) based on specimens collected in the Argentinian provinces of Chaco and Formosa. The new species is characterized by a derived carotid circulatory pattern, a feature shared with O. concolor, O. mamorae, and O. sydandersoni. A unique combination of morphological, morphometric, and molecular characters, however, provides unambiguous evidence of its validity as a separate entity. Individuals of the new species are larger than other representatives of Oecomys, and their skulls have wide and cuneate interorbital regions with well-developed supraorbital shelves, long incisive foramina, long palates, absent alisphenoid struts, and broad Eustachian tubes. This new Oecomys appears to be endemic to the Humid Chaco, an ecoregion listed as Vulnerable due to the human impact. Preliminary observations suggest that several specimens from Eastern Paraguay and the Brazilian Pantanal could also be assigned to the new species described herein.

Una nueva especie es adicionada al altamente diverso género de roedores Oecomys (Cricetidae, Sigmodontinae, Oryzomyini), sobre la base de especímenes coleccionados en las provincias Argentinas de Chaco y Formosa. La nueva especie se caracteriza por un patrón de circulación carotídea derivado, un rasgo compartido con O. concolor, O. mamorae y O. sydandersoni. Sin embargo, la combinación única de caracteres morfológicos, morfométricos y moleculares provee evidencia inequívoca sobre su validez como una entidad separada. Individuos de la nueva especie son de mayor tamaño en comparación con otros Oecomys y sus cráneos tienen una región interorbitaria ancha y acuñada con plataformas supraorbitarias bien desarrolladas, forámenes incisivos largos, paladares largos, ausencia de las barras alisfenoideas y tubos de Eustaquio anchos. Este nuevo Oecomys parece ser endémico del Chaco Húmedo, una ecorregión considerada como Vulnerable debido al impacto antrópico. Observaciones preliminares sugieren que varios especímenes de Paraguay Oriental y del Pantanal Brasilero podrían también ser asignados a la nueva especie aquí descrita.