Leaf-eared mice (genus Phyllotis) are among the most widespread and abundant small mammals in the Andean Altiplano, but species boundaries and distributional limits are often poorly delineated due to sparse survey data from remote mountains and high-elevation deserts. Here, we report a combined analysis of mitochondrial DNA variation and whole-genome sequence (WGS) variation in Phyllotis mice to delimit species boundaries, to assess the timescale of diversification of the group, and to examine evidence for interspecific hybridization. Estimates of divergence based on cytb data suggest that most diversification of Phyllotis occurred during the past 3 million years. Consistent with the Pleistocene Aridification hypothesis, our results suggest that diversification of Phyllotis largely coincided with climatically induced environmental changes in the mid- to late-Pleistocene. Contrary to the Montane Uplift hypothesis, most diversification in the group occurred well after the major phase of uplift of the Central Andean Plateau. Species delimitation analyses revealed surprising patterns of cryptic diversity within several nominal forms, suggesting the presence of much undescribed alpha diversity in the genus. Results of genomic analyses revealed evidence of hybridization between the sister species P. limatus and P. vaccarum, suggesting that the contemporary zone of range overlap between the two species represents a hybrid zone.

Based on a diverse Late-Holocene (1889–1743 cal yrs BP) small mammal assemblage (14 species, 204 individuals) resulting from the trophic activity of owls, we reconstruct the paleoenvironmental conditions of Las Chacritas area, Catamarca Province, northwestern Argentina. Twenty modern and one additional Late-Holocene samples from the region were used as comparative parameters in the paleoenvironmental reconstruction. Through direct comparison with a present-day assemblage from Las Chacritas, and using Nonmetric Multidimensional Scaling, spatial and temporal beta diversity (employing the Sorensen dissimilarity index), and the temporal beta diversity index (TBI) including all the small mammal samples, we quantitatively reconstruct the relationships among modern and Late-Holocene assemblages. Direct comparison showed significant differences, with relative abundances changing markedly over time, with several species of the Late-Holocene assemblage absent in the modern sample whereas many species frequent in the modern community absent in the Late-Holocene. NMDS analysis associated the Late-Holocene assemblage with modern samples of western drier environments. Beta diversity was low for presence-absence and moderate for abundance data, with higher contribution of turnover than nestedness, although for abundance data the proportion of nestedness was higher. TBI showed high variation among both Holocene sites and their present-day counterparts, whereas species gains dominated in modern samples. Our results suggest that the habitats surrounding Las Chacritas have modified markedly since the Late-Holocene. Presence of species today frequent in arid environments and absence of forest-dwelling species suggest that open, dry and relatively rocky habitats characterized this area in that interval.

The Andes are known to be one of the most species-rich regions on Earth, with their origination promoting formation of new habitats and acting as climatic barriers. This orogenic event was structured latitudinally with 3 major segments having different formation times and with different environmental and historical conditions. The Andean region has been historically important in the evolutionary history of small mammals and is considered the region of Earth with the highest values of rodent species richness and turnover. Therefore, the region provides an excellent opportunity to evaluate mechanisms involved in structuring rodent assemblages and beta diversity patterns. Here, we assessed spatial patterns of rodent beta diversity along the Andes Mountains, with specific goals of examining patterns of turnover and nestedness as 2 recognized processes that drive species composition. We explored the role of spatial, climate, and historical factors on beta diversity patterns using geographic range maps for 432 rodent species to construct a species presence-absence matrix. We used piecewise regressions to identify latitudinal breakpoints in turnover and nestedness, and conducted multiple regressions and variation-partitioning approaches to assess the contribution of each set of postulated drivers in shaping beta diversity patterns. Beta diversity decreases from north to south. The highest turnover was located at the Northern Andes (5 degrees N and 10 degrees S) and western-central Andes (20 degrees S and 35 degrees S). Nestedness was higher below 40 degrees S and in some areas of the western-central Andes between 15 degrees and 20 degrees S. Turnover and nestedness registered breakpoints coincident with the Central and Southern Andes limit. Turnover explained most of the beta diversity for all segments, although within the Southern Andes there was also some contribution of nestedness. In all segments, beta diversity was mainly explained by spatial factors with minor contributions from spatially structured climate (Northern Andes), interaction of all factors (Central Andes), and the interaction between current climate and history (Southern Andes). Beta diversity of Andean rodents decreases latitudinally, with turnover as the dominant process and nestedness with higher contribution in the Southern Andes. Beta diversity break points partially support Andean orogenic history reflected among latitudinal segments. Figure 3 of this manuscript is recommended for promoting this research. Los Andes son reconocidos como una de las regiones mas ricas en especies de la tierra, ya que su levantamiento favorecio la formacion de nuevos habitats y actuo como barrera climatica. Este evento orogenico se estructuro latitudinalmente en 3 segmentos, cada uno con tiempos de formacion caracteristicas ambientales y condiciones historicas diferentes. La region Andina ha sido un importante escenario en la historia evolutiva de los pequenos mamiferos y es considerada la region con mayor riqueza y recambio de especies. Por lo tanto, es un excelente escenario para evaluar los mecanismos que estructuran los patrones de diversidad beta del ensamble de roedores. Aqui evaluamos el patron espacial de la diversidad beta de roedores a lo largo de la Cordillera de los Andes, descomponiendolo en recambio y anidamiento, con el fin de comprender los procesos subyacentes que determinan la composicion de especies. Exploramos el papel de los factores espaciales, climaticos e historicos sobre los patrones de diversidad beta utilizando mapas de distribucion geografica para 432 especies de roedores obtenidos de la Base de Datos de Diversidad de Mamiferos y construimos una matriz de presencia-ausencia de especies (PAM). Utilizamos regresiones por tramos (picewise) para identificar los puntos de quiebre latitudinales en recambio y anidamiento, y realizamos regresiones multiples y particion de la varianza para evaluar la contribucion de cada conjunto de factores en la conformacion de los patrones de diversidad beta. La diversidad beta disminuye de Norte a Sur, con un mayor recambio en los Andes del Norte (5 degrees N y 10 degrees S) y en la zona central oeste (20 degrees S y 35 degrees S). El anidamiento fue mas alto por debajo de los 40o S y en algunas areas del centro oeste entre los 15 degrees y 20 degrees S. Tanto el recambio como el anidamiento registraron puntos de quiebre coincidentes con el limite entre el segmento Central y el Sur. El recambio explica la mayor parte de la diversidad beta para todos los segmentos, aunque el anidamiento contribuye tambien a la diversidad beta de los Andes del Sur. En todos los segmentos andinos la diversidad beta se explico principalmente por factores espaciales con una menor contribucion del clima actual (NA), por la interaccion de todos los factores (CA) y la interaccion entre el clima historico con el actual (SA).

Abstract The genus Ctenomys Blainville, 1826 includes 68 living species of small to medium-sized (100–1200 g) caviomorph rodents of subterranean habits. During the last decade, this genus has been the subject of numerous taxonomic studies, including the description of new species and the proposal of novel synonyms. Based on phylogenetic analysis of mitochondrial DNA sequences and qualitative and quantitative morphological traits, here we review the species boundaries of the tuco-tucos of the species group of C. mendocinus and describe a new species. The new species is morphologically distinct from other phylogenetically and geographically close species of Ctenomys (e.g., C. fochi, C. mendocinus), showing several differences in their craniodental traits (e.g., proportionally longer nasals and less globose tympanic bullae). The new species occurs in montane grasslands and shrublands of northwestern Mendoza (ca. 2710 m a.s.l.) and in lowlands (ca. 1000 m a.s.l.) of the Monte Desert ecoregion in an area highly impacted by accelerated processes associated with the wine industry.

Ctenomys fochi es una de las especies menos estudiadas del género. Hasta el momento solo ha sido documentada en dos localidades en Argentina, Chumbicha (provincia de Catamarca) y Estancia La Providencia (provincia de Córdoba). Sobre la base del estudio de caracteres morfológicos y genéticos de materiales depositados en la colección de mamíferos del Museo Argentino de Ciencias Naturales, en esta nota reportamos el primer registro de la especie para la provincia de Santiago del Estero (Finca Zorro Pozo, aproximadamente 8,6 km al OSO de Isca Yacu, dpto. Giménez) y discutimos las implicancias de la extensión del rango distribucional en el contexto de su estatus de conservación.

Oxymycterus incluye 17 especies de roedores sigmodontinos de tama & ntilde;o peque & ntilde;o a mediano. La taxonom & iacute;a del g & eacute;nero ha sido relativamente estudiada, pero a & uacute;n persisten numerosos problemas taxon & oacute;micos sin resolver. Un ejemplo de esto lo constituye el tax & oacute;n Oxymycterus paramensis, el cual ha sido asociado a varias formas nominales, cuya distinci & oacute;n no se ha evaluado mediante una aproximaci & oacute;n integrativa. En este estudio, bas & aacute;ndonos en an & aacute;lisis filogen & eacute;ticos de secuencias del gen Cytb, morfol & oacute;gicos sobre caracteres cualitativos y cuantitativos y de modelado de nicho ambiental y geogr & aacute;fico (pasado y presente), re-examinamos el estatus taxon & oacute;mico de las formas nominales akodontius, jacentior y paramensis considerando a la especie recientemente descrita O. willkaurco. La reconstrucci & oacute;n filogen & eacute;tica gui & oacute; los an & aacute;lisis subsecuentes de variaci & oacute;n morfol & oacute;gica y el desarrollo de los modelos de nicho. Considerando los resultados en un contexto integrativo, observamos congruencia entre filogenia, modelos de distribuci & oacute;n y de nicho ambiental, lo cual apoya el reconocimiento de dos especies dentro del concepto de O. paramensis s.l. Al mismo tiempo, la evidencia morfol & oacute;gica no es congruente con esta hip & oacute;tesis taxon & oacute;mica, dado que hay ausencia de caracteres cualitativos diagn & oacute;sticos y diferenciaci & oacute;n morfom & eacute;trica entre estas especies. Teniendo en cuenta que algunas l & iacute;neas de evidencia indican la posibilidad de interrupciones de flujo g & eacute;nico, consideramos que existe mayor apoyo para el reconocimiento de dos taxa a nivel de especie, O. paramensis, end & eacute;mico de Bolivia y O. akodontius (el cual tiene prioridad sobre jacentior), distribuido desde el sur de Bolivia hasta el noroeste de Argentina. Sin embargo, recomendamos que se realicen estudios m & aacute;s detallados para poner a prueba el escenario taxon & oacute;mico propuesto aqu & iacute;.

Rodentia has a high species number and chromosomal variability. The South American genus Akodon is one of the most speciose muroids, with more than 40 species included in several species groups. Here, we characterize cytogenetically specimens of Akodon from central-western Argentina. Subsequently, we reviewed and analyzed the cytogenetic data for this genus, build a phylogeny and mapped chromosome changes to interpret its evolution. Specimens of A. dolores from central-western Argentina have 2n=42-44/FNa=44 (46, 48) due to a Robertsonian rearrangement. Our data expand the distribution range known for this polymorphism and confirm its geographic structure. Other specimens had 2n=40/FNa=40, representing populations of A. oenos, A. polopi, and A. spegazzinii. All karyotypes have a low amount of heterochromatin, concentrated in centromeres and sex chromosomes, as in other rodents. The complement with 2n=40/FNa=40 is the most frequent in Akodon and is shared by most species in some groups. Chromosome numbers are very diverse. The FNa shows less variability; FNa=42 was recovered as ancestral, excluding A. mimus, which was connected at the base of the Akodon tree and has FNa=44. This indicates a complex chromosome evolution in Akodon, and suggests that reductions and increases in the 2n and FNa evolved independently in some lineages.

The genus Ctenomys of subterranean rodents is one of the most species-rich genera of Mammalia, with 66 living species currently recognized. However, the taxonomy of the genus is dynamic with several new species and new synonymies proposed during the last decade. One of the species groups that have undergone more changes in contents in the last years is the Ctenomys mendocinus species group. Here, based on phylogenetic analysis of mitochondrial DNA sequences and qualitative and quantitative morphological evidence, we conducted an appraisal of the species richness of tuco-tucos of the C. mendocinus species group, describing two new species from west-central Argentina. The new taxa are morphometrically distinctive when compared with other geographically or phylogenetically close species of the genus, showing qualitative differences in their craniodental anatomy. One of the new species is known from the eastern Andean slopes of La Rioja and San Juan provinces, occurring on montane grasslands and shrublands above 3,500 m a.s.l., while the other is endemic of southwestern Mendoza province, occurring on montane grasslands and shrublands between 2,400–2,700 m a.s.l. In addition, we include for the first time the nominal forms C. fochi and C. validus in a phylogenetic analysis of the genus Ctenomys, showing that both correspond to the C. mendocinus species group, being the second a junior synonym of C. mendocinus. Finally, we made some comments about other candidate species within this species group as well as highlight issues that need to be addressed to gain a robust picture of the specific richness of Ctenomys.

The genus Microcavia includes six species of terrestrial, medium-sized, living cavies that occupy arid to semiarid environments at both high and low elevations in western and southern South America. Among these, Microcavia shiptoni is one of the least known species, being recorded only at two isolated localities from northwestern Argentina. Genetic information and a detailed morphological characterization are lacking for this elusive species. In this work, we start filling these gaps by including M. shiptoni in a phylogenetic analysis based on mitochondrial DNA sequences that includes five of the six currently recognized species and place M. shiptoni as sister to M. niata in a clade of highland species. In addition, using both qualitative and quantitative morphological traits, we provided an emended diagnosis for this taxon and a key for the living species of the genus. Finally, we present, the first notes on the natural history of this species.

A partir del estudio de dos muestras de egagrópilas de Tyto furcata colectadas en Alumbrera, a 1650 m s.n.m. en el extremo norte del Campo del Pucará, departamento Andalgalá, Catamarca, Argentina, presentamos un novedoso registro para el roedor sigmodontino Andalgalomys olrogi Williams and Mares, 1978. Documentamos por primera vez la presencia de esta especie a más de 1300 m de altitud y en un ambiente de pastizales de neblina de Yungas (parcialmente modificados por actividades antrópicas). Su escasa representación en las muestras estudiadas (menor a 1,6%) sugiere que el Campo del Pucará representa un área marginal dentro de su rango de distribución.

Optimising conservation efforts requires an accurate record of the extant species as well as their geographic distributions. Nevertheless, most current conservation strategies start from an incomplete biodiversity inventory. Argentina has an extraordinary diversity of species, however, until now an updated inventory of its fauna has not been carried out. In this context, the main objective of this work is to present the results of the first national inventory of vertebrate species. Experts from each major vertebrate taxonomic group assembled and compiled its respective inventory. The information gathered included taxonomic rank, conservation status, endemism and geographic distribution. Species richness and representativeness were calculated for each taxonomic group, distinguishing between native, endemic and exotic, for each Argentinian province. Our results show Argentina harbours 3,303 species: 574 marine fish, 561 freshwater fish, 177 amphibians, 450 reptiles, 1,113 birds, and 428 mammals. Native species constitute 98.1% of the total taxa. The results achieved were spatially represented showing a pattern of higher richness from north to south and from east to west. Species considered as threatened account for 17.8% and 15.2% are endemic. There are five Extinct species. These results provide key information on developing strategies and public policies at the national and provincial levels and constitute a tool for the management and conservation of biodiversity.

Oligoryzomys longicaudatus se distribuye por las laderas orientales y occidentales de los Andes en el extremo sur de Sudamérica. En el sur de Argentina presenta una distribución relativamente bien conocida, pero hacia el norte, en coincidencia con la existencia de poblaciones aparentemente discontinuas, sus límites geográficos no están bien establecidos. Durante una revisión de especímenes de Oligoryzomys depositados en la Colección Mamíferos Lillo registramos dos ejemplares provenientes de la provincia de San Luis que fueron asignados a esta especie a partir de comparaciones cuantitativas y cualitativas del cráneo. Sobre estos ejemplares, citamos por primera vez a la especie para esta provincia y el Chaco Seco, destacando la importancia del registro para el conocimiento de su distribución.

En 2021, Jayat et al. propusimos una nueva especie de roedor sigmodontino, nombrada Phyllotis pehuenche, para las poblaciones del complejo de especies de Phyllotis xanthopygus del sudoeste de la provincia de Mendoza y el oeste de la provincia de Neuquén, Argentina. La descripción formal de la especie, publicada en un material suplementario electrónico modificable, no cumple con los requerimientos establecidos en la enmienda sobre publicaciones electrónicas (ICZN 2012) de la Cuarta Edición del Código Internacional de Nomenclatura Zoológica (ICZN 1999), haciendo que el nombre no esté disponible. El objetivo de esta nota es cumplir con los requerimientos del código y hacer el nombre disponible. Aquí ofrecemos una versión resumida de la descripción original de esta especie. En esta nota, ofrecemos un tratamiento taxonómico para P. pehuenche, incluyendo su sinonimia, localidad tipo, holotipo y paratipos, proveyendo la etimología del epíteto específico, y ofreciendo una diagnosis para la especie y comentarios acerca de su distribución geográfica. Con toda la información provista, cumplimos con los lineamientos del Código Internacional de Nomenclatura Zoológica (ICZN 1999, 2012) haciendo el nombre disponible.