Search

Thomasomys is the most diverse genus of the Sigmodontinae subfamily, comprising at least 51 species. Despite recent systematic advances, the monophyly of this genus, the proposed species groups and their content, and the species limits are not yet firmly established. Using a well‐sampled mitochondrial dataset, we aim to test the monophyly of the genus, infer phylogenetic relationships among species and species groups and test the limits between valid species and candidate species. For this, we used a large matrix of 272 partial non‐redundant sequences of the cytochrome b mitochondrial gene from 40 valid and 20 candidate species. Using probabilistic approaches on this dataset, we inferred Thomasomys phylogenetic relationships and explored species boundaries using four unilocus species delimitation methods (ABGD, ASAP, bPTP and GMYC). Thomasomys sensu stricto was recovered monophyletic and well‐supported, excluding a Peruvian lineage misidentified as part of the genus. Analyses consistently recovered 10 well‐supported major clades and several paraphyletic or polyphyletic species. Delimitation methods and genetic divergences estimated that Thomasomys comprises between 81 and 93 putative species, thus potentially doubling the species diversity of Thomasomys. Such a result clearly calls for an urgent taxonomic revision of this genus and the use of further molecular loci within an integrative taxonomic approach to describe its diversity and understand its evolutionary history. [ABSTRACT FROM AUTHOR]

The classification of rodent species can be challenging due to high morphological similarities observed among them. This problem is further increased in palaeontological systematics, where classification is traditionally based on the molar morphology. The subfamily Arvicolinae (Rodentia, Mammalia) is one of these rodent groups, whose classification being important for biostratigraphic and climatic studies of the Quaternary period is challenging. We present an application developed using the MatLab informatic algorithm, designed to classify the Arvicolinae species using Geometric Morphometrics (GMM) analyses of the first lower molar. Moreover, the application includes an option to automatically obtain the linear measurements that are commonly used for the identification of these species. This method shows a high degree of accuracy in the species classification, which is expected to increase as the reference database is further developed. This application can serve as an alternative tool for the classification of specimens with unclear morphologies. It can also be used to reduce the time required to manually obtain the linear indices necessary for their classification. [ABSTRACT FROM AUTHOR]

Oecomys cleberi is an arboreal rodent little known reagarding its natural history, distribution, and ecology. In this paper, we present new records of O. cleberi within a region of the Atlantic Forest, in a transition zone with Cerrado, in the northwestern state of São Paulo. We investigated the effects of the structure of fragmented landscapes on its occurrence at 40 sites in this region. We detected O. cleberi only in seasonal semideciduous forests and palm forests, but not in pastures, wetlands, and young reforestation. Our results indicated that its occurrence was determined by the amount of habitat within a 500 m radius landscape, and extremely low occupancy probabilities in landscapes with less than 25% forest cover (ψ < 0.3). Our results show the importance of the amount of habitat at the landscape scale for the occurrence of Oecomys cleberi, and point out that most of the landscapes in the study region presented low occupancy probabilities by this forest rodent. Although O. cleberi should not be considered as an Atlantic Forest species, it seems to be a resident species in ecotone areas with Cerrado, within the Atlantic Forest domain. Thus, conservation actions are necessary to preserve their populations in these regions. [ABSTRACT FROM AUTHOR]

ABSTRACT Canopy mammals constitute a diverse and widely distributed group. However, these species have not been widely studied, and there are currently many gaps in our knowledge of their ecology, behaviour, distribution, and conservation status. We identified crucial trends and omissions in terms of research effort on research themes, taxonomic groups, countries, and protected areas (PAs) and geographic information biases. A systematic review was conducted by consulting two electronic databases (Web of Science and Scopus), including research conducted within neotropical countries (from central Mexico to northern Argentina) until the end of the first half of 2021. All the references obtained were reviewed and categorised, and the geographical location of each study was extracted to evaluate geographical gaps. We found that two orders (Carnivora and Didelphimorphia) and three families (Didelphidae, Felidae, and Cricetidae) were the most studied taxa, and were featured in more than 50% of cases. Brazil had the highest number of studies. Topics concerning diseases (19% of cases), distribution (14%), and ecology (14%) were the most frequently addressed; only 4.6% of the studies focused on anthropogenic disturbances, and less than 30% of the studies were conducted within PAs. We found that one of the largest and most important geographical biases in knowledge was in the northern Amazon region, where the number of studies was low or null. This study lays the groundwork for future research on these understudied mammals, to develop better research that can allow us to design more appropriate conservation strategies. [ABSTRACT FROM AUTHOR]

Research into the hunting behavior in members of the Cricetidae family offers an opportunity to reveal what changes in the predatory behavioral sequences occur when a rodent species shifts from an omnivorous to a predatory lifestyle. The study tests the following hypotheses: are there phylogenetic differences in the divergence of species' predatory lifestyles in hamsters or do ecological factors lead to shaping their hunting behavior? We applied the data compression approach for performing comparative analysis of hunting patterns as biological "texts." The study presents a comparative analysis of hunting behaviors in five Cricetinae species, focusing on the new data obtained for the desert hamster Phodopus roborovskii whose behavior has never been studied before. The hunting behavior of P. roborovskii appeared to be the most variable one. In contrast, behavioral sequences in P. campbelli and Allocricetulus curtatus display more significant order and predictability of behavior during hunting. Optional hunting behavior in the most ancient species P. roborovskii displayed similarities with obligate patterns in "young" Allocricetulus species. It thus turned out to be the most advanced hunter among members of the Phodopus genus. Differences in hunting sequences among Phodopus representatives suggest that the hunting behavior of these species, despite its optional mode, was subject to selection during species splitting within the genus. These results did not reveal the role played by phylogenetic differences in the divergence of species' predatory lifestyles. They suggested that ecological conditions are the main factors in speciation of the hunting behavior in hamsters. [ABSTRACT FROM AUTHOR]

Introduction:Rhipidomys is the second most specious and the most widespread genus of the tribe Thomasomyini. Chromosomal data have been an important tool in the taxonomy of the group that presents low variability of diploid number (2n) and highly variable fundamental numbers (FNs). Despite such diversity, the genus has been studied mainly by classical and banding cytogenetic techniques. Methods: This study performed a comparative study between R. emiliae (2n = 44, FN = 52), R. macrurus (2n = 44, FN = 49), R. nitela (2n = 50, FN = 71), and R. mastacalis (2n = 44, FN = 72) using chromosome painting probes of two Oryzomyini species. Results: Our analysis revealed pericentric inversion as the main rearrangement involved in the karyotype evolution of the group, although tandem fusions/fissions were also detected. In addition, we detected eight syntenic associations exclusive of the genus Rhipidomys, and three syntenic associations shared between species of the tribe Thomasomyini and Oryzomyini. Conclusion: Comparative cytogenetic analysis by ZOO-FISH on genus Rhipidomys supports a pattern of chromosomal rearrangement already suggested by comparative G-banding. However, the results suggest that karyotype variability in the genus could also involve the occurrence of an evolutionary new centromere. [ABSTRACT FROM AUTHOR]

Although the order Rodentia does not present a high risk of extinction compared to mammals as a whole, several families demonstrate high levels of threat and/or data deficiency, therefore highlighting the need for targeted research and the application of ecological and reproductive data to the development of conservation actions. The order Rodentia, the largest among mammals, includes 9 families, and the family Cricetidae is the most diverse of the Brazilian rodents. In Brazil, 12 of the 16 genera of Oecomys are found. Oecomys bicolor is known in Brazil as the 'arboreal rat' and is, found in dry, deciduous and tropical forests. The mean body weight of Oecomys bicolor was 35.8 g and the gonadal, tubular and epithelial somatic indexes were, 0.53%, 0.47% and 0.37%, respectively. Seminiferous tubules volume density was 89.72% and the mitotic and meiotic indexes corresponded to 8.59 and 2.45 cells, respectively, and the yield of spermatogenesis was 23.83 cells. The intertubular compartment represented 10.28% of the testis parenchyma and around 5% of the interstitial space was occupied by Leydig cells, whose number per gram of testis was 11.10 × 107 cells. By evaluating the biometric and histomorphometric characteristics of the testis, there is evidence that this species has a high investment in reproduction. Due to the high contribution of the seminiferous epithelium and the intertubular compartment in this species, compared to the others of the same family, it is possible to infer that the species Oecomys bicolor has a promiscuous reproductive behaviour. [ABSTRACT FROM AUTHOR]

The abundant and widely distributed deermice Peromyscus leucopus and P. maniculatus are important reservoirs for several different zoonotic agents in North America. For the pathogens they persistently harbor, these species are also examples of the phenomenon of infection tolerance. In the present study a prior observation of absent expression of the high-affinity Fc immunoglobulin gamma receptor I (FcγRI), or CD64, in P. leucopus was confirmed in an experimental infection with Borreliella burgdorferi, a Lyme disease agent. We demonstrate that the null phenotype is attributable to a long-standing inactivation of the Fcgr1 gene in both species by a deletion of the promoter and coding sequence for the signal peptide for FcγRI. The Fcgr1 pseudogene was also documented in the related species P. polionotus. Six other Peromyscus species, including P. californicus, have coding sequences for a full-length FcγRI, including a consensus signal peptide. An inference from reported phenotypes for null Fcgr1 mutations engineered in Mus musculus is that one consequence of pseudogenization of Fcgr1 is comparatively less inflammation during infection than in animals, including humans, with undisrupted, fully active genes.

Tick-borne infectious agents (TBIAs) include several bacteria and protozoa that can infect vertebrates, including humans. Some of these agents can cause important diseases from both a public health perspective, such as Lyme disease, and from an animal health and production viewpoint, such as Texas fever. In Chile, several studies have assessed the presence of tick-borne disease agents in vectors and mammal hosts, mainly in the northern regions, but few studies have assessed the presence of these agents in Central and Southern Chile. This study aimed to assess the presence of three groups of TBIAs--Borrelia, Anaplasmataceae, and Piroplasmida--in cricetid rodents of Central and Southern Chile. A total of 207 specimens from 13 localities between the O'Higgins and Los Lagos regions were captured. DNA was extracted from the liver and spleen, and subsequently underwent polymerase chain reaction (PCR) amplification targeting the 16S rRNA, flaB, and 18S rRNA genes to detect DNA from Borrelia, Anaplasmataceae, and Piroplasmida, respectively. Although no DNA from these TBIAs was detected, the DNA extraction process was validated by optimal DNA purity ratios (an A260/A280 ratio within the 1.6-2.0 range) and successful internal control amplification in all samples. These results, in addition to findings from previous reports, suggest a very low prevalence of these TBIAs in the rodent population studied. Further research into the factors influencing the presence of these agents and their vectors will provide insight into the reasons underlying this low prevalence. [ABSTRACT FROM AUTHOR]

Oryzomys texensisAllen, 1894, the Texas Marsh Rice Rat, is a yellowish gray-brown oryzomyine rodent with whitish feet and venter, black eyes, small hairy ears, short vibrissae, and a tail about one-half of total length. It was elevated to species status based on the results of an extensive molecular genetics analysis of the O. palustris complex. The poorly defined eastern boundary of O. texensis includes Mississippi, Arkansas, southern Missouri, and southern Illinois, with populations extending westward to southeastern Kansas, eastern Oklahoma, eastern and coastal Texas, into northeastern Tamaulipas, Mexico. Present in tidal marshes and other habitats near water, O. texensis is omnivorous, with some populations being highly carnivorous. Resumen: Oryzomys texensisAllen, 1894, es un roedor de la tribu Oryzomyini, de color marrón grisáceo amarillento con pies y vientre blanquecinos, ojos negros, pequeñas orejas velludas, vibrisas cortas y una cola que constituye aproximadamente la mitad de su longitud total. Fue elevado del nivel de subespecie de O. palustris a especie en base a resultados de un extenso análisis de genética molecular del complejo O. palustris. El margen oriental de la distribución geográfica de O. texensis está mal definido e incluye partes de Mississippi y Arkansas, así como el sur de Missouri y sur de Illinois, con poblaciones adicionales extendiéndose en dirección oeste hacia el sureste de Kansas, este de Oklahoma, planicie costera y este de Texas y hasta el extremo suroccidental de Texas y noroeste de Tamaulipas, México. Está presente en marismas, humedales, y otros hábitats cercanos al agua. Si bien es omnívoro, algunas poblaciones constan de individuos mayormente carnívoros. [ABSTRACT FROM AUTHOR]

Genetic structure of the Maximowicz's vole Alexandromys maximowiczii was assessed using data on the mtDNA control region variability, and the high level of genetic variability was revealed for the species as a whole. Three phylogenetic groups ("east," "west," and "south") were distinguished, and within the "east" group, three subclades ("Chit," "Amur," and "Khab") were identified. All phylogenetic groups and subclades were characterized by mainly allopatric geographical distribution across the species range with one "hybrid" sampling found in the vicinity of the settlement of Savvo-Borzya (Zabaykalsky krai), the individuals of which had different variants of the mt genotype. One individual carried the "west" variant, and the second one—the "east"/"Amur" variant. The revealed phylogeographic structure was generally congruent with the differentiation pattern as revealed by the chromosomal forms, but did not agree with the previously accepted subspecies system. Complex intraspecific subdivision of the Maximowicz's vole, revealed at different organization levels (molecular genetic, as well as chromosomal), reflects not only complex geography of the study area, but also the history of dynamic changes in the natural environment. [ABSTRACT FROM AUTHOR]

We analyzed the geographical distribution of Habromys species based on distributional data from museum specimens, web databases, and literature. We recorded species-presence data of each species in 0.5° × 0.5° grid cells and biogeographic provinces in Mexico and Central America. We analyzed the association between vegetation types and land use. We carried out species distribution models of most species of Habromys and those tree species frequently harboring these mice, finding a high distributional congruence among mice and trees. Species of Habromys occur throughout the montane systems of Mexico and northern Central America, so they can be considered characteristic elements of the Neotropical montane cloud forests. All species of the genus occur in Mexico, whereas Guatemala and El Salvador have only one species. Although all species of Habromys are highly restricted and considered rare species, only one (H. simulatus) is currently protected by Mexican laws. We assigned two species to a high and four to the critical conservation risk. Habromys species contribute to the recognition of Mesoamerica as a biodiversity hotspot. [ABSTRACT FROM AUTHOR]

The arboreal rodent Oecomys cleberi was previously considered endemic to the Cerrado domain in central-western Brazil. We report on a range extension of O. cleberi to the Atlantic Forest domain of São Paulo, and add new records to Mato Grosso do Sul and Minas Gerais states, totaling 10 new records. Based on a large sample of O. cleberi, we did not find evidence for sexual dimorphism. Our results revealed that specimens of O. cleberi from Cerrado and Atlantic Forest are larger than O. bicolor from the Amazon. Moreover, the larger buccinator–masticatory/foramen ovale confluence in O. cleberi allowed further distinction to O. bicolor. We also provide further details of morphological variation within O. cleberi. Reproductive males and females of O. cleberi were recorded in the rainy season, between December and January, and one male was infested by the mite Gigantolaelaps canestrinii. Our new records show that this arboreal rodent is also present in seasonal forests within the domain of the Atlantic Forest. We suggest that this species, typical of the Cerrado, occurs only marginally in the Atlantic Forest of São Paulo. [ABSTRACT FROM AUTHOR]

The Brazilian Atlantic Forest has undergone significant transformation, resulting in habitat loss and the endangerment of many species of mammals and other vertebrates. In this study, the presence of fluctuating asymmetry of four anatomical structures of the arboreal rodent Rhipidomys mastacalis was evaluated using geometric morphometrics. The study focused on adult specimens collected in a mosaic of vegetation composed of forested vegetation, occupancy mosaics in forested areas, and cocoa plantations. The results showed significant values of fluctuating asymmetries in all structures and in all areas. The skulls and scapulae showed the highest values of asymmetry in forested vegetation and cocoa plantations, while the mandibles showed the greatest values in forested vegetation, and the pelvis in occupancy mosaics and cocoa plantations. These findings are consistent with previous studies that have evaluated developmental stability in mammals and suggest that high asymmetry values indicate an effect on different phases of ontogeny, which can harm the survival of a species in future generations. Overall, this study provides important insights into the impacts of habitat fragmentation on Rhipidomys mastacalis and highlights the need for conservation efforts to preserve the integrity of the Brazilian Atlantic Forest and its diverse range of wildlife. [ABSTRACT FROM AUTHOR]

The intestinal trematode fauna of the Water Vole Arvicola amphibius, (previously A. terrestris), was investigated to determine whether it might provide evidence of an animal component in the diet of this aquatic herbivorous small mammal. Interrogation of the electronic Host-Parasite Database of the Natural History Museum London revealed the presence of fourteen species of intestinal trematode in water voles, infection with each of which would require the ingestion of tissue from an animal intermediate host. The results obtained using these parasite indicators provide convincing evidence of animal components in the diet of A. amphibius and support anecdotal reports of water voles feeding on animal material in the field.

Orthohantaviruses are diverse zoonotic RNA viruses. Small mammals, such as mice and rats are common chronic, asymptomatic hosts that transmit the virus through their feces and urine. In North America, hantavirus infection primarily causes hantavirus cardiopulmonary syndrome (HCPS), which has a mortality rate of nearly 36%. In the United States of America, New Mexico (NM) is leading the nation in the number of HCPS-reported cases (N = 129). However, no reported cases of HCPS have occurred within eastern NM. In this study, we assessed the prevalence of Sin Nombre virus (SNV) in rodent assemblages across eastern NM, using RT-qPCR. We screened for potential rodent hosts in the region, as well as identified areas that may pose significant infection risk to humans. We captured and collected blood and lung tissues from 738 rodents belonging to 23 species. 167 individuals from 16 different species were positive for SNV RNA by RT-qPCR, including 6 species unreported in the literature: Onychomys leucogaster (Northern grasshopper mouse), Dipodomys merriami (Merriam's kangaroo rat), Dipodomys ordii (Ord's kangaroo rat), Dipodomys spectabilis (Banner-tailed kangaroo rat), Perognathus flavus (Silky pocket mouse), and Chaetodipus hispidus (Hispid pocket mouse). The infection rates did not differ between sexes or rodent families (i.e., Cricetidae vs. Heteromyidae). Generalized linear model showed that disturbed habitat types positively influenced the prevalence of SNV at sites of survey. Overall, the results of this study indicate that many rodent species in east New Mexico have the potential to maintain SNV in the environment, but further research is needed to assess species specific infectivity mechanisms and potential risk to humans. [ABSTRACT FROM AUTHOR]

Argentinian fossil records of Bibimys have been well documented in a Late Pleistocene palaeontological site and several Late Holocene archaeological sites in Buenos Aires province. However, the specimen reported here is the first fossil record of this genus from the Early Holocene in Argentina. It was recovered in a fluvial unit dated at 9990 ± 140 yr B.P. from Doll creek, southwestern Entre Ríos province, Argentina. At present, this genus is distributed in the distal area of the Paraná River Delta in the province of Entre Ríos, represented by the species B. torresi, and in the province of Misiones, northern Corrientes, and eastern Chaco and Formosa, represented by the species B. chacoensis. The specimen described here is a contribution to the palaeobiogeography of the genus and to a better understanding of the fossil sigmodontine fauna that inhabited the southwest of the province of Entre Ríos in the recent past. [ABSTRACT FROM AUTHOR]

Among South American countries, Paraguay is one of the least studied in terms of its fauna and flora. Although its small mammal fauna, including sigmodontine rodents (Cricetidae), is becoming better known, their ectoparasites are scarcely known. As part of a study on the effects of habitat fragmentation in the Interior Atlantic Forest in eastern Paraguay, multiple dimensions of terrestrial small mammals in three major reserves were surveyed. The aim of this study is to identify the ectoparasites collected on the most abundant rodents and to describe, visualize and quantify the parasite-host relationships. Ectoparasites obtained by brushing the fur of the rodents were preserved in vials with 96% ethanol. Mites were then fixed, cleared with lactophenol, and mounted between slides with Hoyer’s medium for identification with optical microscopes. Mites (Mesostigmata, Laelapidae) were the only ectoparasites collected (n = 189), from rodents (n = 22) identified as Hylaeamys megacephalus, Oligoryzomys nigripes, Akodon montensis, and A. paranaensis. Mites identified on rodent hosts varied from Androlaelaps fahrenholzi and Gigantolaelaps oudemansi on H. megacephalus; A. fahrenholzi, Gigantolaelaps wolffsohni, Mysolaelaps parvispinosus and Laelaps paulistanensis on O. nigripes; A. fahrenholzi and Androlaelaps misionalis on A. montensis; and Androlaelaps sp., and A. fahrenholzi on A. paranaensis. Except for A. fahrenholzi, the remaining laelapid species herein reported constitute the first records for Paraguay. However, these parasite-host relationships have been documented in neighboring countries. Thus, the results obtained herein are valuable as they improve the knowledge of the fauna in Paraguay and contribute to the knowledge mite-host specificity. [ABSTRACT FROM AUTHOR]

Abstract—Features of the breeding and population structure of the root vole inhabiting the Southern Trans-Ural region during the periods of 1981–2001 and 2020–2022 are considered. Animals were captured during both winter and snowless periods. A total of 754 root voles were captured using ditches with pitfalls (guide fences made of polyethylene film) and trap lines. As in the other parts of their range, root voles in the Southern Trans-Ural region prefer near-water habitats. Winter breeding is characteristic of this rodent in the Southern Trans-Ural region, but the most intensive breeding is observed in May–June. These months are also characterized by the maximum fecundity for both overwintered and young females. Overwintered females can produce up to four litters during their reproductive period, while young females can produce 3–4 litters. The fecundity of overwintered females is statistically significantly higher than that of young ones. In the months February–May, overwintered animals dominate in the root vole population, while in June and the following summer and autumn months, underyearlings predominate. Males dominate among the overwintered and underyearling animals; at the end of summer and in the autumn, the sex ratio among these age groups of root voles levels off. [ABSTRACT FROM AUTHOR]

Abstract—Based on our analysis of long-term (2015–2021) observations carried out at a registration spot in Gagarin Park (Simferopol, Crimea), patterns were revealed in the spatial distribution of burrows of the common hamster (Cricetus cricetus L., 1758) depending on the state of the tree and shrub layer, as well as disturbance factors. It is shown that the leading factor influencing the spatial distribution of burrows is the location of trees, and the total number of burrows is mainly affected by the projective covering by shrubs. These factors were revealed as a result of cluster analysis for the spatial–geographical formulation of the problem and cross-correlation analysis. It is assumed that the use of spatial modeling makes it possible to identify environmental factors including plant communities influencing the choice and exploitation of microhabitats by animals, as well as to find approaches to the analysis of the implementation of behavioral patterns during the development and exploitation of a habitat. [ABSTRACT FROM AUTHOR]

The effect of multiple paternity on the development of the humoral immune response in Syrian hamster pups was studied. The paternity type was found to be determined by ten microsatellite markers. Pups were immunized with T-dependent antigens (fissurella hemocyanin, KLH) at 33 days of age, with the level of specific antibodies (anti-KLH IgG) measured in blood samples at 5, 10, 20, and 25 days after immunization. As much as 24% of pups from multiple paternity broods and 25% from single paternity broods were revealed to develop no immune response. At the same time, in all pups that responded to immunization, the level of anti-KLH IgG significantly increased over time, starting with the 5th day after immunization. However, there were no significant differences in the concentration of anti-KLH IgG in the blood serum of pups derived from broods with multiple paternity or from litters obtained from one male. Therefore, our results fail to support the hypothesis that multiple paternity enhances the immunity of Syrian hamster pups. [ABSTRACT FROM AUTHOR]

Based on material collected in western Siberia in the second half of summer in the period from 1954 to 2016, both on the plains and in the mountains, the distribution of forest voles was analyzed in the zonal and provincial aspects. Based on cluster analysis of the matrix of similarity coefficients of the abundance indicators, habitat classifications were compiled according to the degree of favorable environmental conditions for each of the study species. Based on the classifications, the species abundance as related to environmental factors and their inseparable combinations (natural and anthropogenic regimes) were established. [ABSTRACT FROM AUTHOR]

Archive data were analyzed concerning the reproduction of yellow steppe lemmings (Eolagurus luteus) in the Moscow Zoo. We used information referring to E. luteus pairs that existed during two periods: 2008–2013 (first colony) and 2017–2020 (second colony). All breeding partners in the first colony had at least one common ancestor (they originated from two females and one male) and thus were closely related to each other. The degree of relatedness of partners in the second colony was much lower. The founders of that colony were five females and five males that had originated from four pairs of unrelated individuals live-trapped in the Zaisan Basin. We conducted a comparative assessment of the life expectancy and reproductive parameters of adult yellow steppe lemmings and the survival of their offspring in two colonies, that is, we observed the effect of different degrees of inbreeding on such parameters. We also assessed the effect of female age on those values. We assigned the females to two age categories: younger (age of 15–59 days by the time of pair establishment) and older (age of 60–701 days) category. The results of statistical analysis confirmed the significant influence of the degree of relatedness of partners on the proportion of reproducing females, the number of litters per pair, the number of survived pups per pair, the mean number of pups per litter, the inter-birth interval, the female life expectancy, and the period of pair existence. The influence of female age on these parameters was insignificant. Our data provide evidence for a pronounced inbreeding depression in the first captive colony of the yellow steppe lemming. [ABSTRACT FROM AUTHOR]

The strategies to cope the repetitive cycles of hypoxia/reoxygenation associated with diving may vary among different mammal species. The aim of this research was to analyze the antioxidant defenses in tissues of semiaquatic rodents, such as Ondatra zibethicus (L., 1766), Arvicola amphibius (L., 1758) and non-diving closely related rodent species—Myodes glareolus (Schreber, 1780) and Alexandromys oeconomus (Pallas, 1776). Adult females and males were captured in August–September in northwestern Russia (Republic of Karelia). Revealed species-specific differences in the studied values suggest that O. zibethicus, the larger animal with longer dive duration, possess the greater enzymatic antioxidant capacity in their tissues than A. amphibius, which tissues frequently rely on the low molecular weight antioxidant glutathione.The results of this study support the hypothesis that besides having common or very similar adaptations of the antioxidant system to diving hypoxia/reoxygenation the closely related rodent species possess different adjustments or strategies of these adaptations that is species-dependent and probably connected with oxygen stores, basal metabolic rate and diving behavior. [ABSTRACT FROM AUTHOR]

Rodents are notable for their unique life history traits that render a fast-breeding capacity. Their short generation times allow local adaptations to appear, and several studies have tried to understand if—and how—geographical variables influence local adaptation in life history traits. We compared demographic and life history traits of the Neotropical cricetid Necromys lasiurus based on 7,400 museum specimens collected daily and simultaneously over 5 years at several sites in the Caatinga biogeographic domain subject to heterogeneous geographic and climatological variables. This sample, assembled by the National Plague Service between 1951 and 1955, includes skulls, skins, and individual specimen data currently deposited in the Museu Nacional (Rio de Janeiro, Brazil). Based on this material, we analyzed population fluctuation, breeding season, sexual size dimorphism, sexual maturity, and litter size. We also hypothesized that geographic variables (elevation, rainfall, temperature, longitude, and latitude) influence key life history traits, such as size at birth and litter size. Overall, N. lasiurus showed plastic reproductive patterns, with few traits shared among populations. Notably, there is strong seasonal variation in population fluctuation patterns, breeding events clumped in early dry season and old individuals distributed throughout all the year, as has been seen for populations in other biomes. Geography had no influence on size at birth but litter size was explained by the interaction between maternal weight and geographical variables. Plastic life history traits so intimately responsive to climatological variables likely contribute to N. lasiurus having one of the largest geographic ranges among Neotropical cricetids, as well as to its status as the most important plague reservoir in the Caatinga domain. [ABSTRACT FROM AUTHOR]

The subgenus Aschizomys belongs to the genus Alticola (Central Asian mountain vole) and consists of two species: Alticola macrotis and Alticola lemminus. Phylogenetic relationships within the subgenus Aschizomys remain obscure due to limited sampling, an insufficient number of molecular markers used in phylogenetic studies, and paraphyly observed on mitochondrial trees. In this work, to infer reliable phylogenetic relationships and evaluate putative scenarios of ancient hybridization within the subgenus, we applied double‐digest restriction site‐associated DNA paired‐end (quaddRAD) sequencing to 20 DNA samples (20 individuals), including five species of the genus Alticola, and dated the divergence of cytochrome b (cytb) lineages within Aschizomys using a "second calibration" approach. We showed monophyly of the two species on the basis of thousands of nuclear loci and demonstrated traces of introgression also in the nuclear genome. Observed paraphyly in cytb could be explained by an introgression event rather than incomplete lineage sorting. This explanation was confirmed by an analysis of the cytb divergence time. Overall, our results support the hypothesis of extensive migration of the Aschizomys species during the Late Pleistocene, with this migration leading to population divergence and introgression. We expect our article to become a starting point for a series of rigorous studies on the population history of the genus Alticola as a whole. [ABSTRACT FROM AUTHOR]

It was found that the variability of additional elements in the posterior part of the first and second upper molars in L. gregalis forms a morphological module with a hierarchical structure. This module is designated as an atypical form (Atypical Form), and its phenotype iss AF. The phenotype of the typical form is designated as tf (typical form). The main component of modular variability is an increase in the frequency of individuals with the AF phenotype with age. The severity of this phenotype also increases with age. The presence of the AF phenotype in individuals is determined monogenically. Individuals with the AF phenotype are dominant heterozygotes or homozygotes. Which phenotype (tf or AF) the dominant heterozygote implements may depend on the influence of modifier genes. The revealed morphological module of the presence of additional elements in the posterior part of the first and second upper molars has a genetic basis. [ABSTRACT FROM AUTHOR]

The arboreal rice rat of the genus Oecomys Thomas, 1906 is one of the most speciose genera of the subfamily Sigmodontinae, with 19 species currently recognized and occurring from eastern Panama to northern Argentina, Paraguay, and in northern, central and eastern Brazil. Herein we describe a new species using an integrative approach based on molecular, morphological, and morphometric data. We used in our assessment recently collected specimens from the states of Pará and Rondônia, one of the most deforested regions in Brazil. We examined 51 specimens of Oecomys from museum collections including name-bearing types from most of the distributional range of the genus. We also sequenced 32 specimens of Oecomys, and for the molecular analyses, we used the mitochondrial marker Cytochrome b and the nuclear marker intron 7 of β-fibrinogen. Our mitochondrial marker results recovered a strongly supported clade composed of two divergent clades (3.78%), one including lineages of O. bicolor and O. cleberi, and the other clade representing the new species. The topology of concatenated mitochondrial and nuclear data also recovered Oecomys sp. nov. as a sister lineage of the O. bicolor and O. cleberi clade. Also, both markers recovered new lineages from the O. bicolor and O. cleberi species group. The new species can be discriminated from other Oecomys species by pelage colour and craniodental characters, such as absent or small mastoid fenestra, and the presence of alisphenoid strut, small subsquamosal fenestra, presence of sphenopalatine vacuities, and presence of accessory loph of M1 and M2 paracones. The new species occurs exclusively in the Rondônia centre of endemism, delimited by the rivers Amazon to the north, Tapajós to the east, and Madeira to the west. The description of this new Oecomys increases the diversity, and also contributes to elevate Amazonian Sigmodontinae species richness and endemism in this still poorly known biome. [ABSTRACT FROM AUTHOR]

Northern bog lemmings, Mictomys (Synaptomys) borealis, are currently being assessed for protections under the U.S. Endangered Species Act. A major impediment to comprehensive evaluation is a deficiency of data towards understanding the biology of these rodents. Inherent rarity and scarce specimen sampling, despite a continent-wide distribution, has precluded our ability to implement modern methods for resolving taxonomy, evolutionary history, and investigating multiple other species traits. Here we use a maternally inherited locus (mitochondrial cytochrome b) and between 5939 and 11 513 nuclear loci from reduced representation sequencing (ddRADseq) to investigate the evolutionary history of northern bog lemmings. We (1) qualify evidence based on morphological and early molecular studies for the genus assignment of Mictomys, (2) test the validity of multiple sub-species designations, (3) provide spatial and temporal historical biogeographic perspectives, and (4) discuss how incomplete sampling might influence conservation efforts. Both mitochondrial and nuclear datasets exhibit deep divergence and paraphyly between two recognized species, the northern (Mictomys borealis) and southern (Synaptomys cooperi) bog lemmings. Based on mtDNA, the geographically isolated subspecies (M. b. sphagnicola) was found to be divergent from all other specimens. The remainder of the species exhibited shallow intra-specific differentiation in mtDNA, however, nuclear data supports genetic distinction consistent with four geographic subspecies. Recent coalescence of all northern bog lemmings (except for M. b. sphagnicola) reflects divergence in multiple refugia through the last glacial cycle, including a well-known coastal center of endemism and multiple regions south of continental ice sheets. Regional lineages across North America suggest strong latitudinal displacement with global climate change, coupled with isolation-reconnection dynamics. This taxon suffers from a lack of modern samples through most of its distribution, severely limiting the interpretation of ongoing evolutionary processes, particularly in southern portions of the species' range. Limited voucher specimen sampling of vulnerable populations could aid in rigorous conservation decision-making. [ABSTRACT FROM AUTHOR]

Background: During early mammalian development, DNA methylation undergoes two waves of reprogramming, enabling transitions between somatic cells, oocyte and embryo. The first wave of de novo DNA methylation establishment occurs in oocytes. Its molecular mechanisms have been studied in mouse, a classical mammalian model. Current model describes DNA methyltransferase 3A (DNMT3A) and its cofactor DNMT3L as two essential factors for oocyte DNA methylation—the ablation of either leads to nearly complete abrogation of DNA methylation. However, DNMT3L is not expressed in human oocytes, suggesting that the mechanism uncovered in mouse is not universal across mammals. Results: We analysed available RNA-seq data sets from oocytes of multiple mammals, including our novel data sets of several rodent species, and revealed that Dnmt3l is expressed only in the oocytes of mouse, rat and golden hamster, and at a low level in guinea pigs. We identified a specific promoter sequence recognised by an oocyte transcription factor complex associated with strong Dnmt3l activity and demonstrated that it emerged in the rodent clade Eumuroida, comprising the families Muridae (mice, rats, gerbils) and Cricetidae (hamsters). In addition, an evolutionarily novel promoter emerged in the guinea pig, driving weak Dnmt3l expression, likely without functional relevance. Therefore, Dnmt3l is expressed and consequently plays a role in oocyte de novo DNA methylation only in a small number of rodent species, instead of being an essential pan-mammalian factor. In contrast to somatic cells, where catalytically inactive DNMT3B interacts with DNMT3A, forming a heterotetramer, we did not find evidence for the expression of such inactive Dnmt3b isoforms in the oocytes of the tested species. Conclusions: The analysis of RNA-seq data and genomic sequences revealed that DNMT3L is likely to play a role in oocytes de novo DNA methylation only in mice, rats, gerbils and hamsters. The mechanism governing de novo DNA methylation in the oocytes of most mammalian species, including humans, occurs through a yet unknown mechanism that differs from the current model discovered in mouse. [ABSTRACT FROM AUTHOR]

The sudden appearance of modern cricetids in Europe during the Early Miocene was one of the most significant mammalian events of European Neogene. A characteristic representative of this mammalian turnover was the genus Megacricetodon that quickly became major components of the rodent faunas across Europe. Here, we review the fossil record of this genus from the Early-Middle Miocene (MN4-MN5) localities of Czech Republic, the key area for the understanding the earliest history of this genus in central Europe. We provide an age refinement of the localities under study, especially in the context of new data from the Northern Alpine Foreland Basins. A detailed analysis of the available material revealed a presence of Megacricetodon grueneri sp. nov., described here from Dolnice 3 (MN4a/b). The oldest record of Megacricetodon comes from Ořechov (~late MN4a) and marks the first occurrence of the genus in central Europe. We discuss and propose the most likely scenarios for the earliest phylogeny and dispersal of Megacricetodon into central and western Europe that were strongly influenced by major tectonic processes in the Pannonian and Pre-Alpine areas having a major impact on the development of terrestrial ecosystems and the composition of faunas. Zoobank: [ABSTRACT FROM AUTHOR]

The genus Euryoryzomys encompasses six species found across Cis-Andean lowland and montane rainforests in South America. One of the most enigmatic forms of the genus is found in the Brejos de altitude of north-eastern Brazil, where enclaves of dense rainforest in mountain ranges sharply contrast with surrounding semi-arid Caatinga. Here we analyse morphological and molecular data, and demonstrate that these populations are members of a new species, which is described and contrasted with other Euryoryzomys. Phylogenetic analyses based on mitochondrial cytochrome b gene, coupled with morphometrics and comparative anatomy analyses, show that the new species differs from its sister-species, Euryoryzomys lamia from the Cerrado of Central Brazil, and from other forms of the genus, corroborating previous perspectives based on karyological data. The new species of the genus occurs in two distinct areas in the state of Ceará, Serra de Ibiapaba and Serra de Baturité, and one isolated range in Paraíba state. The recovered biogeographic pattern of Brejos de altitude —Cerrado sister-group relationship is novel among studied vertebrates, as most species from Brejos are more closely related to taxa from Amazon and Atlantic Forest. Further taxonomic efforts are necessary to uncover the total diversity within Euryoryzomys, especially for the nominal taxa E. emmonsae, E. macconnelli , and E. nitidus. [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]

Fossil vertebrates, especially mammals, of the Neogene-Quaternary of Central Argentina were fundamental to the construction of time and rock-time scales and the knowledge of the biotic evolution of southern South America. The poverty of fossiliferous localities constrained with radiometric and/or paleomagnetic data heavily complicated the correlation of different faunas and their temporal allocation. The Cerro Azul Formation (Argentina) constitutes a suitable example of this situation but also enlarged because its fossils have been collected from scattered and isolated small outcrops whose chronological ordering was based on the "stage of evolution" of some rodents. We present here new dates for the fauna/locality of Telén (La Pampa Province) plus extensive biochronological analyses covering 16 fossiliferous localities referred to Cerro Azul Formation. Two dates from an "escoria" sample gave 7.09 Ma for Telén assemblage, an age in accordance with that obtained from an independent faunal analysis. Faunal ordination and age obtained with regression analyses identify a succession of faunas/localities that cover the time range between 8-5.33 Ma. The older assemblages (e.g., Cerro Bota) appear to be transitional between Chasicoan and "Huayquerian" faunas. The first records of procyonids and cricetid rodents, two North American lineages, are not synchronic (7 and 5.7 Ma, respectively). Our results show important temporal overlapping among the proposed successive rodent "biozones". The use of the "stage of evolution" in the analyses does not improve the results, suggesting that its application without independent chronological/biostratigraphical constraints is not appropriate. [ABSTRACT FROM AUTHOR]

Oryzomys palustris (Harlan, 1837), the common marsh rice rat, is an Oryzomyine rodent with a tail nearly as long as the head and body, grayish above and white below with long-toed white feet. This account is an update of Mammalian Species 176 on the subject species by James L. Wolfe (1982a), incorporating 103 new references, most published since 1982. Oryzomys palustris, one of six living and two extinct species in this Neotropical genus, is semiaquatic and omnivorous, being highly carnivorous in some populations. It is parapatric with O. texensis in the western portion of its distribution in the southern United States. Oryzomys palustris is classified as "Least Concern" (LC) on the International Union for Conservation of Nature Red List. [ABSTRACT FROM AUTHOR]

The Crested-tailed deer mouse, Habromys lophurus, is one of seven arboreal species within the genus Habromys. Species of this genus are monotypic, relatively rare, and occur in low densities. Their geographical distribution is highly fragmented due to being restricted to montane cloud forest in Mesoamerica and they are of conservation concern. All Habromys species are endemic to Mexico, except H. lophurus, which is also distributed in Guatemala and El Salvador. In this study, we obtained and characterized the first mitogenome and several thousand nuclear ultraconserved elements (UCEs) of H. lophurus to determine its phylogenetic position within neotomine-peromyscine mice. Its mitogenome sequence (16,509 bp) is only the second complete mitogenome obtained for this poorly known genus. We also obtained the first nuclear genomic data for H. lophurus, including 3,654 UCE loci, as well as a partial mitogenome of H. simulatus (6,349 bp), and 2,186 UCE for the outgroup Holochilus sciureus. Phylogenetic analyses that included our newly generated genomic data coupled with previously published data from other neotomine-peromyscine mice confirm the placement of H. lophurus, H. simulatus, and H. ixtlani within a highly supported clade. The Habromys clade was nested within a clade that also contains members of the genus Peromyscus and provides further support for the hypothesis of the paraphyly of Peromyscus. These genomic resources will contribute to future phylogenomic studies that aim to further elucidate the evolutionary history of this rare and critically endangered genus of rodents. [ABSTRACT FROM AUTHOR]

Repetitive DNA are sequences repeated hundreds or thousands of times and an abundant part of eukaryotic genomes. SatDNA represents the majority of the repetitive sequences, followed by transposable elements. The species Holochilus nanus (HNA) belongs to the rodent tribe Oryzomyini, the most taxonomically diverse of Sigmodontinae subfamily. Cytogenetic studies on Oryzomyini reflect such diversity by revealing an exceptional range of karyotype variability. However, little is known about the repetitive DNA content and its involvement in chromosomal diversification of these species. In the search for a more detailed understanding about the composition of repetitive DNA on the genome of HNA and other species of Oryzomyini, we employed a combination of bioinformatic, cytogenetic and molecular techniques to characterize the repetitive DNA content of these species. RepeatExplorer analysis showed that almost half of repetitive content of HNA genome are composed by Long Terminal Repeats and a less significant portion are composed by Short Interspersed Nuclear Elements and Long Interspersed Nuclear Elements. RepeatMasker showed that more than 30% of HNA genome are composed by repetitive sequences, with two main waves of repetitive element insertion. It was also possible to identify a satellite DNA sequence present in the centromeric region of Oryzomyini species, and a repetitive sequence enriched on the long arm of HNA X chromosome. Also, comparative analysis between HNA genome with and without B chromosome did not evidence any repeat element enriched on the supernumerary, suggesting that B chromosome of HNA is composed by a fraction of repeats from all the genome. [ABSTRACT FROM AUTHOR]

Parasites are integral members of the global biodiversity. They are useful indicators of environmental stress, food web structure and diversity. Ectoparasites have the potential to transmit vector-borne diseases of public health and veterinary importance and to play an important role in the regulation and evolution of host populations. The interlinkages between hosts, parasites and the environment are complex and challenging to study, leading to controversial results. Most previous studies have been focused on one or two parasite groups, while hosts are often co-infected by different taxa. The present study aims to assess the influence of environmental and host traits on the entire ectoparasite community composition of the rodent Akodon azarae. A total of 278 rodents were examined and mites (Mesostigmata), lice (Phthiraptera), ticks (Ixodida) and fleas (Siphonaptera) were determined. A multi-correspondence analysis was performed in order to analyze interactions within the ectoparasite community and the influence of environmental and host variables on this assembly. We found that environmental variables have a stronger influence on the composition of the ectoparasite community of A. azarae than the host variables analyzed. Minimum temperature was the most influential variable among the studied. In addition, we found evidence of agonistic and antagonistic interactions between ticks and mites, lice and fleas. The present study supports the hypothesis that minimum temperature plays a major role in the dynamics that shape the ectoparasite community of A. azarae, probably through both direct and indirect processes. This finding becomes particularly relevant in a climate change scenario. [ABSTRACT FROM AUTHOR]

Genetic studies in the highlands of Mexico have revealed extensive intraspecific differentiation and highly structured genetic variation in rodents and other taxa. One of the most important and complex systems in these highlands is the Trans-Mexican Volcanic Belt (TMVB), a biogeographic region located in central Mexico. Recent studies suggest strong structure and undiscovered diversity within the TMVB highlands, which indicates more study of endemic species is warranted. One of these species is the endemic Volcano Harvest Mouse Reithrodontomys chrysopsis, which inhabits small and fragmented patches at high altitudes. This mouse is poorly known, under-represented in field collections, and has been the subject of few studies of phylogenetics, taxonomy, and evolutionary history. This study aimed to assess the phylogenetic and intraspecific relationships of R. chrysopsis throughout its known geographic distribution to better understand the evolutionary patterns of it and other TMVB mammals. Our phylogenetic analyses using Cytb and Fgb-I7 markers revealed that R. chrysopsis is sister to R. sumichrasti and R. megalotis, which contrasts with a previous hypothesis based on morphological data. Genetic differentiation, divergence time, and species delimitation analyses showed three main divergent lineages within R. chrysopsis, located at the western, central, and eastern TMVB. These lineages diverged during the Pliocene-Pleistocene interval. Our results support the hypothesis that volcanic activity and climatic oscillations during the Pleistocene in central Mexico promoted diversification processes within the TMVB. Further molecular and morphological studies will be needed to provide information for the taxonomic designation of the east divergent lineage detected herein. [ABSTRACT FROM AUTHOR]

The Atlantic Forest harbors a large species richness and high levels of endemism, but the processes that shaped its biodiversity are poorly studied, especially for mammals. Among them are the endemic mice Juliomys, which comprise forest dwellers distributed in southeastern and southern Brazil, northeastern Argentina, and eastern Paraguay. In this study, we investigate the phylogenetic relationships among species and perform phylogeographic analyses to evaluate the population structure and demographic scenarios through mitochondrial gene cytochrome b sequences. We investigate three hypotheses of diversification (forest refuges, montane isolate, and geomorphological events) to understand the evolution of the Juliomys species. Phylogenetic analyses recovered five clades/lineages, four of which are congruent with species currently recognized. The fifth lineage expands the range of the genus 659 km to the north and may represent a new species. The observed demographic and geographic structure of genetic diversity does not match the forest refuge hypothesis as mechanism to explain the diversification in Juliomys. Our results recovered J. rimofrons and J. ximenezi as sister species, supporting predictions of montane isolate hypothesis. We also detected a shallow genetic structure in J. pictipes and J. ossitenuis. Both phylogeographic breaks were congruent with limits of the São Paulo Basin, an area that has undergone Neogene reactivations of tectonic faults. It is suggested that geomorphological events led to a deformed landscape that influenced the dynamics of sedimentary basins and promoted an incipient population structure in J. pictipes and J. ossitenuis. Our findings demonstrate that the divergences whithin Juliomys species occurred during the Quaternary, too recently to have produced strong geographic structure. [ABSTRACT FROM AUTHOR]

Neacomys is a genus of small spiny or bristly sigmodontine rodents that are common components of mammalian faunas in multiple biomes on Central and South America. Recent studies on this group have demonstrated that there is cryptic diversity yet to be discovered within currently recognized species that have not received comprehensive revisions, as well as in areas that have been overlooked. Here we ratify this assertion by describing a new species previously misidentified as the Narrow-footed Spiny Mouse (Neacomys tenuipes) from the Chocó biogeographic region in northwestern Ecuador, Neacomys marci Brito & Tinoco, sp. nov. Distinctiveness of this entity is supported by the combination of the following morphological characters: small size (head-body length 65–85 mm); long tail (69–126% longer than head-body length); pale buff-colored but gray-based belly fur; white throat; hypothenar pad usually absent; long nasals; and a condylar process higher than the coronoid process. Likewise genetic distance analyses and phylogenetic reconstructions based on cytochrome-b (Cytb) sequence data indicate a clear divergence from typical populations of N. tenuipes, and a sister relationship between them. The results presented here increase the diversity of Neacomys to 24 species, placing it among the most diverse genera within the sigmodontine rodents. [ABSTRACT FROM AUTHOR]

Species boundaries are difficult to establish in groups with very similar morphology. As an alternative, it has been suggested to integrate multiple sources of data to clarify taxonomic problems in taxa where cryptic speciation processes have been reported. This is the case of the harvest mouse Reithrodontomys mexicanus, which has a problematic taxonomy history as it is considered a complex species. Here, we evaluate the cryptic diversity of R. mexicanus using an integrative taxonomy approach in order to detect candidate lineages at the species level. The molecular analysis used one mitochondrial (cytb) and two nuclear (Fgb‐I7 and IRBP) genes. Species hypotheses were suggested based on three molecular delimitation methods (mPTP, bGMYC, and STACEY) and cytb genetic distance values. Skull and environmental space differences between the delimited species were also tested to complement the discrimination of candidate species. Based on the consensus across the delimitation methods and genetic distance values, four species were proposed, which were mostly supported by morphometric and ecological data: R. mexicanus clade I, R. mexicanus clade IIA, R. mexicanus clade IIIA, and R. mexicanus clade IIIB. In addition, the evolutionary relationships between the species that comprise the R. mexicanus group were discussed from a phylogenetic approach. Our findings present important taxonomic implications for Reithrodontomys, as the number of known species for this genus increases. Furthermore, we highlight the importance of the use of multiple sources of data in systematic studies to establish robust delimitations between species considered taxonomically complex. [ABSTRACT FROM AUTHOR]

Rodentia is the most speciose order of mammals, and they are known to harbor a wide range of viruses. Although there has been significant research on zoonotic viruses in rodents, research on the diversity of other viruses has been limited, especially for rodents in the families Cricetidae and Heteromyidae. In fecal and liver samples of nine species of rodents, we identify 346 distinct circular DNA viral genomes. Of these, a large portion are circular, single-stranded DNA viruses in the families Anelloviridae (n = 3), Circoviridae (n = 5), Genomoviridae (n = 7), Microviridae (n = 297), Naryaviridae (n = 4), Vilyaviridae (n = 15) and in the phylum Cressdnaviricota (n = 13) that cannot be assigned established families. We also identified two large bacteriophages of 36 and 50 kb that are part of the class Caudoviricetes. Some of these viruses are clearly those that infect rodents, however, most of these likely infect various organisms associated with rodents, their environment or their diet. • Subsampled rodent material collected as part biocollections and researchers. • 346 distinct circular viral genomes in rodent fecal (n = 10) and liver (n = 3) samples. • ∼86% of these new viral genomes are microviruses. • 93% of these identified viral genomes represent new species. • 15 viral genomes cannot be assigned to currently established families. [ABSTRACT FROM AUTHOR]

The Quaternary glaciations had great impacts on the historical biogeography of small mammal species. Recent studies have showed the effects of these climatic cycles on the diversification of several Neotropical rodents, but these have focused on species whose distributions do not encompass the tropical Andes. Thus, the influences of these climatic dynamics on the evolutionary history of tropical Andean rodent species remain unknown. The effects of these climatic changes were addressed on Aepeomys lugens and A. reigi, two Thomasomyine endemics from the Cordillera de Mérida in the Venezuelan Andes. The past potential geographic distribution of both species was inferred using an ecological niche modeling approach. The estimations obtained indicated that the availability of the suitable climatic conditions for these taxa has varied in size and location during the last 140,000 years. The spatial projection of the niche models onto the climatic scenarios explored indicates that the effects over the historical distributions were smaller in A. lugens than in A. reigi. These results show that the current geographic distribution of both Andean rodents conceals complex biogeographic histories, and characterizations of the demographic history and genetic diversity will be required to understand the evolution of the genus Aepeomys in the Andes. [ABSTRACT FROM AUTHOR]

Simple Summary: Sarcocystidae is a family of protozoa whose life cycles usually include two hosts: an intermediate or paratenic host, where protozoa form tissular cysts, and a definitive host, whose intestines usually become infected after consuming tissular cysts. In Chile, studies of sarcocystids have been performed mostly on domestic animals, and scarce data are available from wildlife. A total of 207 rodents, encompassing six native species, from 13 localities in Central and Southern Chile, were studied to assess the presence of Sarcocystidae. DNA was isolated from several tissues and phylogenetic analyses were performed. Blood smear examinations and histological studies of several organs were performed. Overall, three individuals of rodents were PCR-positive and three different genotypes were retrieved belonging to Sarcocystis, Besnoitia, and Toxoplasmatinae protozoa. No protozoa were found during microscopic examinations. Although it was not possible to confirm whether the findings corresponded to parasitism or accidental encounter, the phylogenetic positions of the genotypes support the hypothesis that they are parasites of rodents. All three genotypes are suggested as potential new taxa in the Sarcocystidae family. In Chile, studies of parasites from the family Sarcocystidae (Apicomplexa) have mostly been related to domestic animals. We aimed to assess the presence of Sarcocystidae taxa in cricetid rodents from Central and Southern Chile. We studied 207 rodents, encompassing six species, from 13 localities. We isolated DNA from tissue samples, amplified the Sarcocystidae 18S rRNA gene with polymerase chain reaction, and performed phylogenetic analyses using maximum likelihood and Bayesian inferences. In addition, we examined blood smears and performed histological studies in organs from Sarcocystidae DNA-positive animals. Three specimens were DNA-positive and three genotypes were retrieved and named: Sarcocystis sp. P61, related to Sarcocystis strixi, was detected in two Abrothrix olivacea. Toxoplasmatinae gen. sp. P99 was retrieved from those same two specimens, and was related to Toxoplasma and other genera, although it branched independently. Besnoitia sp. R34 was detected in one Abrothrix hirta, and was clustered with congeneric species associated with rodents. No protozoa were found during microscopic studies; thus, it was not possible to confirm parasitic interactions rather than accidental encounters. However, the close relatedness of the retrieved genotypes to parasites of rodents supports the hypothesis of host–parasite associations. All three genotypes are suggested as potential new taxa, including a putative new genus. [ABSTRACT FROM AUTHOR]

The cricetid rodent Rhagomys septentrionalis was previously known only from its type locality in Ecuador. Four new records are reported here, documenting a northward range extension of about 300 km. Obtained evidence include, for the first time, nests and a video of an individual in the wild. Distribution models suggest that R. septentrionalis potentially has an ample geographic range along the eastern Andean Forest. According to IUCN criteria the species should be categorized as Vulnerable. The case of R. septentrionalis, now recorded from five localities within a year after its original description, suggests that rarity in sigmodontines is mostly driven by limited field efforts. [ABSTRACT FROM AUTHOR]

A detailed morphological description and comparative study were conducted on numerous large-sized hamster remains collected from the late Middle Pleistocene Locality 2 of Shanyangzhai (Syz 2), Hebei Province, China. The comparisons reveal that these fossils are highly similar to the extant Tscherskia triton in size and morphology, including the small degree of alternating between the main opposite cusps on M1-3, the presence of axioloph on M3, and mesolophids on m1-2 that are present but seldom reach the lingual margin of the teeth, among other features. However, minor differences between the two still exist. Consequently, all these fossils are designated as a chronosubspecies of the extant species, T. triton varians comb. nov. The skull and molar morphologies of Cricetinus varians and T. triton were meticulously compared to resolve the long-standing debate regarding the validity of Cricetinus Zdansky, 1928 and C. varians Zdansky, 1928. The findings indicate that the differences between the two are slight; as a result, C. varians can only be considered a chronosubspecies of T. triton, i.e., T. triton varians comb. nov., and Cricetinus should be recognized as a junior synonym of Tscherskia. We tentatively propose that, among the seven species once referred to Cricetinus, C. europaeus, C. gritzai, C. janossyi, and C. koufosi should be reassigned to Tscherskia, while C. beremendensis should be transferred to Allocricetus, and C. mesolophidos to Neocricetodon. Excluding Tscherskia sp. from the Late Pliocene Youhe fauna, there are no reliable Tscherskia fossils in China earlier than the Middle Pleistocene. Based on the current evidence, Tscherskia may have originated from Neocricetodon during the Early Pliocene in Europe and subsequently spread to Asia. T. triton is its sole surviving representative, which now exclusively inhabits East Asia. [ABSTRACT FROM AUTHOR]

Thomasomys cinereus is the type species of Thomasomys, type genus of the sigmodontine tribe Thomasomyini. As currently recognized, Thomasomys includes 48 species, all of which are endemic to humid montane or premontane forests in the tropical Andes. Although it has been suggested that T. cinereus is a species complex, this hypothesis has yet to be critically evaluated. Herein we provide a revision of the species based on a qualitative assessment of external, craniodental, and soft morphological traits; morphometric analyses; a phylogenetic analysis based on cytochrome b gene sequences; species delimitation methods; and first-hand examination of type material. Our analyses of genetic data recovered four distinct clades within T. cinereus, one corresponding to T. cinereus sensu stricto (restricted to the montane forests delimited by the Río Marañón, Río Huancabamba, and Río Tablachaca in Cajamarca department, Peru) and three new species: Thomasomys lojapiuranus, sp. nov., from the montane forests of Piura department, Peru, and Loja province, Ecuador; T. shallqukucha, sp. nov., restricted to the Kañaris montane forests in the Peruvian department of Lambayeque; and T. pagaibambensis, sp. nov., restricted to the montane forests of Pagaibamba in Cajamarca department, Peru. These species can be distinguished by several discrete morphological traits of the skull, dentition, mandible, stomach, palatal rugae, and glans penis. Genetic distances among these taxa range from 5.06%–7.65% at the cytochrome b locus, and delimitation analyses based on cytochrome b sequence data support their recognition as distinct species. Our results suggest the existence of previously unsuspected dispersal barriers in the Andes of northern Peru, and they confirm that the Río Marañón is a formidable barrier that limits the distribution of species of Thomasomys as well as other sigmodontine rodents. [ABSTRACT FROM AUTHOR]

Species in recent, rapid radiations can be difficult to distinguish from one another due to incomplete sorting of traits, insufficient time for novel morphologies to evolve, and elevated rates of hybridization and gene flow. The vole genus Microtus (58 spp.) is one such system where all three factors are likely at play. In the central United States, the prairie vole, Microtus ochrogaster , and the eastern meadow vole, M. pennsylvanicus , occur in sympatry and can be distinguished on the basis of molar cusp patterns but are known to be exceptionally difficult to distinguish using external morphological characters. Using a combination of morphometrics, pelage color analyses, and phylogenetics, we explored which traits are most effective for species identification and whether these same traits can be used to identify the subspecies M. o. ohionensis. While we were able to identify six traits that differed significantly between M. ochrogaster and M. pennsylvanicus , we also found substantial measurement overlap which limits the utility of these traits for species identification. The subspecies M. o. ohionensis was particularly difficult to distinguish from M. p. pennsylvanicus , and we did not find any evidence that this subspecies forms a distinct genetic clade. Furthermore, the full species M. ochrogaster and M. pennsylvanicus did not form reciprocal clades in phylogenetic analyses. We discuss several possible reasons for these patterns, including unrecognized variation in molar cusp patterns and/or localized hybridization. Overall, our results provide useful information that will aid in the identification of these species and subspecies in the future, and provides a case study of how genetics, morphometrics, and fur color analyses can be used to disentangle signatures of evolutionary history and hybridization. [ABSTRACT FROM AUTHOR]