Extinct insular oryzomyine rice rats (Rodentia: Sigmodontinae) from the Grenada Bank, southern Caribbean.

The Lesser Antillean island chain in the eastern Caribbean formerly supported a diverse rodent fauna including multiple endemic genera of oryzomyine rice rats. The Caribbean rice rats are now all extinct, with most island populations known only from Holocene palaeontological and zooarchaeological material and with many remaining taxonomically undescribed. Rice rat material is reported from several pre-Columbian Ceramic Age (late Holocene) archaeological sites on the Grenada Bank, including sites on Grenada and Carriacou, but the taxonomic identity and diversity of the Grenada Bank rice rats has remained uncertain. We provide a morphology-based description of rice rats from Grenada and Carriacou, and analyze their phylogenetic and biogeographical affinities to other Caribbean and mainland Neotropical oryzomyines. We recognize two taxa from the Grenada Bank: we describe the new species Megalomys camerhogne from Pearls (Grenada), representing the largest-bodied member of the extinct endemic Caribbean genus Megalomys, and we refer smaller-bodied oryzomyine material from Pearls and Sabazan (Carriacou) to the widespread extant Neotropical species Zygodontomys brevicauda. Body size variation within Megalomys correlates with island bank area and might thus reflect historical rather than modern biogeography. Zygodontomys specimens from the Grenada Bank fall within the upper end of size variation in extant populations and may constitute an example of 'island gigantism', but it is possible that occurrence of this widespread species on the Grenada Bank might reflect prehistoric human-mediated translocation. We predict further endemic Caribbean rice rat taxa remain to be discovered, including a possible species of Megalomys on the neighbouring island of St. Vincent.

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

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

Multilocus phylogeny of African striped grass mice (Lemniscomys): Stripe pattern only partly reflects evolutionary relationships.

Murine rodents are one of the most evolutionary successful groups of extant mammals. They are also important for human as vectors and reservoirs of zoonoses and agricultural pests. Unfortunately, their fast and relatively recent diversification impedes our understanding of phylogenetic relationships and species limits of many murine taxa, including those with very conspicuous phenotype that has been frequently used for taxonomic purposes. One of such groups are the striped grass mice (genus Lemniscomys), distributed across sub-Saharan Africa in 11 currently recognized species. These are traditionally classified into three morphological groups according to different pelage colouration on the back: (a) L. barbarus group (three species) with several continuous pale longitudinal stripes; (b) L. striatus group (four species) with pale stripes diffused into short lines or dots; and (c) L. griselda group (four species) with a single mid-dorsal black stripe. Here we reconstructed the most comprehensive molecular phylogeny of the genus Lemniscomys to date, using the largest currently available multi-locus genetic dataset of all but two species. The results show four main lineages (=species complexes) with the distribution corresponding to the major biogeographical regions of Africa. Surprisingly, the four phylogenetic lineages are only in partial agreement with the morphological classification, suggesting that the single-stripe and/or multi-striped phenotypes evolved independently in multiple lineages. Divergence dating showed the split of Lemniscomys and Arvicanthis genera at the beginning of Pleistocene; most of subsequent speciation processes within Lemniscomys were affected by Pleistocene climate oscillations, with predominantly allopatric diversification in fragmented savanna biome. We propose taxonomic suggestions and directions for future research of this striking group of African rodents.

New species boundaries and the diversification history of marsh rat taxa clarify historical connections among ecologically and geographically distinct wetlands of South America.

Taxa with broad geographic ranges that occur in different biomes and exhibit plastic morphological traits and/or adaptations to particular habitats make inferences about species boundaries especially challenging. However, technological and conceptual advances in the generation and analysis of genomic data have advanced the description of biodiversity. Here we address the outstanding questions about the delimitation of species in the genus Holochilus, a rodent with morphological specializations to wetland habitats distributed throughoutthe South America, using genome-wide SNP and morphometric data. Specifically, we apply a Bayesian model-based species delimitation that revealed significant re-arrangements of species boundaries based on consideration of both morphometric and genomic data alone, or in combination. With these shifts in species boundaries, our results provide an insightful framework for inferring the group's biogeographic history and considering possible connections between disjoint biomes in South America. Because of the ecological constraints of the marsh rats, and with the proposed taxonomic re-arrangements, the significance of our findings extends beyond systematics and suggests how diversification might be associated with past ecological/environmental changes during the Pleistocene. Overall, this study highlights how genomic data can provide phylogenetic information for resolving relationships among species of Holochilus, but also the importance of integrative approaches to identify evolutionary independent species. For the relatively understudied vast wetlands of South America, a robust species delimitation framework therefore becomes a critical source of data relevant to hypotheses about the history of the biomes themselves.

Chromosomal Signatures Corroborate the Phylogenetic Relationships within Akodontini (Rodentia, Sigmodontinae).

Comparative chromosome-painting analysis among highly rearranged karyotypes of Sigmodontinae rodents (Rodentia, Cricetidae) detects conserved syntenic blocks, which are proposed as chromosomal signatures and can be used as phylogenetic markers. In the Akodontini tribe, the molecular topology (Cytb and/or IRBP) shows five low-supported clades (divisions: "Akodon", "Bibimys", "Blarinomys", "Oxymycterus", and "Scapteromys") within two high-supported major clades (clade A: "Akodon", "Bibimys", and "Oxymycterus"; clade B: "Blarinomys" and "Scapteromys"). Here, we examine the chromosomal signatures of the Akodontini tribe by using Hylaeamys megacephalus (HME) probes to study the karyotypes of Oxymycterus amazonicus (2n = 54, FN = 64) and Blarinomys breviceps (2n = 28, FN = 50), and compare these data with those from other taxa investigated using the same set of probes. We strategically employ the chromosomal signatures to elucidate phylogenetic relationships among the Akodontini. When we follow the evolution of chromosomal signature states, we find that the cytogenetic data corroborate the current molecular relationships in clade A nodes. We discuss the distinct events that caused karyotypic variability in the Oxymycterus and Blarinomys genera. In addition, we propose that Blarinomys may constitute a species complex, and that the taxonomy should be revised to better delimit the geographical boundaries and their taxonomic status.

Strategies in herbivory by mammals revisited: The role of liver metabolism in a juniper specialist (Neotoma stephensi) and a generalist (Neotoma albigula).

Although herbivory is widespread among mammals, few species have adopted a strategy of dietary specialization. Feeding on a single plant species often exposes herbivores to high doses of plant secondary metabolites (PSMs), which may exceed the animal's detoxification capacities. Theory predicts that specialists will have unique detoxification mechanisms to process high levels of dietary toxins. To evaluate this hypothesis, we compared liver microsomal metabolism of a juniper specialist, Neotoma stephensi (diet >85% juniper), to a generalist, N. albigula (diet ≤30% juniper). Specifically, we quantified the concentration of a key detoxification enzyme, cytochrome P450 2B (CYP2B) in liver microsomes, and the metabolism of α-pinene, the most abundant terpene in the juniper species consumed by the specialist woodrat. In both species, a 30% juniper diet increased the total CYP2B concentration (2-3×) in microsomes and microsomal α-pinene metabolism rates (4-fold). In N. stephensi, higher levels of dietary juniper (60% and 100%) further induced CYP2B and increased metabolism rates of α-pinene. Although no species-specific differences in metabolism rates were observed at 30% dietary juniper, total microsomal CYP2B concentration was 1.7× higher in N. stephensi than in N. albigula (p < .01), suggesting N. stephensi produces one or more variant of CYP2B that is less efficient at processing α-pinene. In N. stephensi, the rates of α-pinene metabolism increased with dietary juniper and were positively correlated with CYP2B concentration. The ability of N. stephensi to elevate CYP2B concentration and rate of α-pinene metabolism with increasing levels of juniper in the diet may facilitate juniper specialization in this species.

Evolution of the Grey-bellied pygmy mouse group: Highly structured molecular diversity with predictable geographic ranges but morphological crypsis.

The grey-bellied pygmy mouse (Mus triton) from the endemic African subgenus Nannomys is a widespread rodent species inhabiting the highlands of eastern and central Africa. Although it has long been considered as a single species, recent data has suggested the existence of a species complex. In order to evaluate the geographical structure and current taxonomy of M. triton, we analysed one mitochondrial and six nuclear genes from individuals covering most of its distribution range. Our analysis revealed the existence of at least five distinct genetic lineages with only marginal overlaps among their distributional ranges. Morphological comparisons, however, showed large overlaps in external body measurements and only a weak differentiation in skull form. Therefore, we suggest maintaining M. triton as a single taxon with pronounced intraspecific genetic structure. Divergence dating analysis placed the most recent common ancestor of the extant lineages of M. triton to the early Pleistocene (about 2.0 Ma). The phylogeographic structure of the species was likely shaped by Pleistocene climatic oscillations and the highly diverse topography of eastern Africa.

Metagenomic sequencing provides insights into microbial detoxification in the guts of small mammalian herbivores (Neotoma spp.).

Microbial detoxification of plant toxins influences the use of plants as food sources by herbivores. Stephen's woodrats (Neotoma stephensi) specialize on juniper, which is defended by oxalate, phenolics and monoterpenes, while closely related N. albigula specialize on cactus, which only contains oxalate. Woodrats maintain two gut chambers harboring dense microbial communities: a foregut chamber proximal to the major site of toxin absorption, and a cecal chamber in their hindgut. We performed several experiments to investigate the location and nature of microbial detoxification in the woodrat gut. First, we measured toxin concentrations across gut chambers of N. stephensi. Compared to food material, oxalate concentrations were immediately lower in the foregut, while concentrations of terpenes remained high in the foregut, and were lowest in the cecal chamber. We conducted metagenomic sequencing of the foregut chambers of both woodrat species and cecal chambers of N. stephensi to compare microbial functions. We found that most genes associated with detoxification were more abundant in the cecal chambers of N. stephensi. However, some genes associated with degradation of oxalate and phenolic compounds were more abundant in the foregut chambers. Thus, microbial detoxification may take place in various chambers depending on the class of chemical compound.

Evolutionary relationships and climatic niche evolution in the genus Handleyomys (Sigmodontinae: Oryzomyini).

Mesoamerica is considered a biodiversity hot spot with levels of endemism and species diversity likely underestimated. Unfortunately, the region continues to experience some of the highest deforestation rates in the world. For mammals, the evolutionary relationships of many endemic taxa are controversial, as it is the case for members of the genus Handleyomys. Estimation of a time-calibrated hypothesis for the evolution of these six genera (Euryoryzomys, Handleyomys, Hylaeamys, Nephelomys, Oecomys and Transandinomys) supported a monophyletic Handleyomys sensu lato. Based on their distinctive morphology and the amount of inter-generic genetic divergence, Handleyomys sensu stricto, H. alfaroi, the H. chapmani, and the H. melanotis species groups warrant recognition as separate genera. In addition, species delimitation documents the existence of cryptic species-level lineages within H. alfaroi and H. rostratus. Cryptic lineages within H. rostratus exhibited significant niche differentiation, but this was not the pattern among species-level clades within H. alfaroi. Similarly, age-range correlations revealed that niche evolution within Handleyomys is not correlated with evolutionary time, instead, ancestral climate tolerance reconstructions show niche disparities at specific diversification events within the chapmani and melanotis species groups, while the climatic niche of the rest of species of Handleyomys tended to be conservative.

Taxonomy of the Phyllotis osilae species group in Argentina; the status of the "Rata de los nogales" (Phyllotis nogalaris Thomas, 1921; Rodentia: Cricetidae).

The taxonomic status of populations of the genus Phyllotis from northwestern Argentina (NWA) has undergone recent changes, with the addition of two species (P. alisosiensis and P. anitae) to the traditionally recognized forms (P. caprinus, P. xanthopygus, and P. osilae). Three of these species (P. anitae, P. osilae, and P. alisosiensis) were included within the Phyllotis osilae species group. Most authors recognized three subspecies of P. osilae for NWA: P. osilae osilae, P. o. nogalaris, and P. o. tucumanus. Morphological, morphometric, and molecular studies based on recently collected specimens suggest that current classification does not reflect the diversity of this group in NWA, revealing the need of some taxonomic reallocations and new distributional delimitations. Here we propose that P. nogalaris must be recognized as a valid species and the restriction of P. osilae to southern Peru and central Bolivia. Following our results, we expect an outstanding improvement in the taxonomic knowledge of the Phyllotis osilae species group in the coming years.

Systematic studies of the genus Aegialomys Weksler, Percequillo and Voss, 2006 (Rodentia: Cricetidae: Sigmodontinae): Annotated catalogue of the types of the species-group taxa.

The genus Aegialomys was described to encompass the former Oryzomys xanthaeolus group, and includes nowadays two species: A. xanthaeolus and A. galapagoensis. Although not very confusing, the taxonomic history of the genus is long, comprising the description of five nominal taxa along the last 180 years: Mus galapagoensis Waterhouse, 1839; Oryzomys bauri Allen, 1892; Oryzomys xanthaeolus Thomas, 1894; Oryzomys  baroni Allen, 1897; and Oryzomys  xanthaeolus ica Osgood, 1944. Here we gathered and documented all available information about the type material of Aegialomys on which the species names were based, re-described their morphometric and morphological characters, commented their synonyms and taxonomic history, and compiled information about type localities. Additionally, we established a neotype for O. bauri in order to define the nominal taxon objectively.

Taxonomic revision of the Andean leaf-eared mouse, Phyllotis andium Thomas 1912 (Rodentia: Cricetidae), with the description of a new species.

The Andean Leaf-eared mouse, Phyllotis andium Thomas 1912, has been considered a widespread medium-size sigmodontine rodent (230 mm of total length and 35 grams approximately) that occurs from Tungurahua, Ecuador, through the Andes, to Lima, Peru. Previous studies performed on Phyllotis noted evidence of morphological geographical variation within the species, which is likely because of the several potential geographical barriers that exist within the distribution range of P. andium. We carried out a taxonomic revision of this species based on qualitative and quantitative morphological analyses of 330 specimens from 92 localities. This included appropriate comparisons with other species of the andium/amicus group and performed molecular analysis based on cytochrome b sequences. As a result, morphologic qualitative analysis suggested the recognition of three different taxa, which are supported by morphologic quantitative and molecular analyses. The three taxa here identified have allopatric distributional ranges separated by important geographic barriers. Following these identification criteria, P. andium is now recognized for the samples from Tungurahua, Ecuador to Huánuco, Peru, and includes melanius and fruticicolus as synonymous; the southern populations from the Ancash and Lima departments, in the western Peruvian Andes, are proposed to represent a new species; and we recognize P. stenops as a valid species with tamborum as a synonym. Finally, we postulate that the diversification of these three species is related to key events in the Andean orogeny.

Transcriptome markers of viral persistence in naturally-infected andes virus (bunyaviridae) seropositive long-tailed pygmy rice rats.

Long-tailed pygmy rice rats (Oligoryzomys longicaudatus) are principal reservoir hosts of Andes virus (ANDV) (Bunyaviridae), which causes most hantavirus cardiopulmonary syndrome cases in the Americas. To develop tools for the study of the ANDV-host interactions, we used RNA-Seq to generate a de novo transcriptome assembly. Splenic RNA from five rice rats captured in Chile, three of which were ANDV-infected, was used to generate an assembly of 66,173 annotated transcripts, including noncoding RNAs. Phylogenetic analysis of selected predicted proteins showed similarities to those of the North American deer mouse (Peromyscus maniculatus), the principal reservoir of Sin Nombre virus (SNV). One of the infected rice rats had about 50-fold more viral burden than the others, suggesting acute infection, whereas the remaining two had levels consistent with persistence. Differential expression analysis revealed distinct signatures among the infected rodents. The differences could be due to 1) variations in viral load, 2) dimorphic or reproductive differences in splenic homing of immune cells, or 3) factors of unknown etiology. In the two persistently infected rice rats, suppression of the JAK-STAT pathway at Stat5b and Ccnot1, elevation of Casp1, RIG-I pathway factors Ppp1cc and Mff, and increased FC receptor-like transcripts occurred. Caspase-1 and Stat5b activation pathways have been shown to stimulate T helper follicular cell (TFH) development in other species. These data are also consistent with reports suggestive of TFH stimulation in deer mice experimentally infected with hantaviruses. In the remaining acutely infected rice rat, the apoptotic pathway marker Cox6a1 was elevated, and putative anti-viral factors Abcb1a, Fam46c, Spp1, Rxra, Rxrb, Trmp2 and Trim58 were modulated. Transcripts for preproenkephalin (Prenk) were reduced, which may be predictive of an increased T cell activation threshold. Taken together, this transcriptome dataset will permit rigorous examination of rice rat-ANDV interactions and may lead to better understanding of virus ecology.

Comparative chromosome painting in six species of Oligoryzomys (Rodentia, Sigmodontinae) and the karyotype evolution of the genus.

Oligoryzomys belongs to the tribe Oryzomyini, and contains about 22 species. Diploid numbers range from 2n = 44 in Oligoryzomys sp. 2 to 2n = 72 in O. utiaritensis and phylogenetic relationships are not well defined. The high morphological convergence leads to misidentification of taxonomic entities and the species are often identified by chromosomal characters. Until now, the genus has been studied only by classical cytogenetic approaches. To understand the chromosomal evolution of Oligoryzomys, we developed chromosome probes from a female of Oligoryzomys moojeni (OMO) with 2n = 70 and hybridized to other five Oligoryzomys species. The probes painted 31 segments on O. fornesi (OFO) with 2n = 62; 32 segments on O. microtis (OMI), 2n = 64; 33 segments on O. nigripes (ONI), 2n = 62 and on O. rupestris (ORU), 2n = 46; and 34 on Oligoryzomys sp. 2 (OSP), 2n = 44. OMO probes 4 and 5 showed a syntenic association in O. fornesi, O. microtis and O. nigripes and were also presented in the same pair, although disrupted, in O. rupestris and Oligoryzomys sp. 2. Concerning O. rupestris and Oligoryzomys sp. 2, species with the lowest diploid numbers of the genus, a total of 8 probes hybridized to 11 segments on the largest pair of ORU 1 and 9 probes hybridized to 12 segments on OSP 1. Also, OMO 6 painted three segments in ORU, corresponding to the proximal segment of ORU 2q, and the whole of ORU 19 and 20. In OSP, the segment corresponding to ORU 20 was homologous to OSP 1p. OMO X showed signals of hybridization in both X and Y chromosomes. Extensive chromosomal rearrangements, that could not be detected by classical cytogenetic techniques, such as pericentric inversions or repositioning of centromeres, Robertsonian rearrangements and tandem fusions/fissions, as well as gain/activation or loss/inactivation of centromeres and telomeric sequences have driven the huge genome reshuffling in these closely related species.

Comparison between Oligoryzomys nigripes and O. flavescens by RAPD and genetic diversity in O. nigripes (Rodentia, Cricetidae).

The genus of Oligoryzomys includes species of small size, morphologically similar, which may impede taxonomic identification, mainly between O. flavescens (Waterhouse, 1837) and O. nigripes (Olfers, 1818). The main objective of this work was to investigate whether the RAPD markers are capable of genetically differentiating the specimens O. nigripes and O. flavescens, coming from Rio Grande do Sul (RS) and Santa Catarina (SC) states, and also to estimate the genetic variability among populations of O. nigripes, with the Uruguay River as a geographical barrier. For this purpose, samples were collected in fragments of forests situated in the North of RS, at FLONA (Floresta Nacional de Passo Fundo) and in fragments from SC, close to the Uruguay River. The karyotyping of two samples for each species was carried out and compared using the RAPD technique together with non- karyotyped individuals. Samples of O. nigripes presented 2n = 62; NA = 82, with submetacentric arms on the largest chromosomes, while samples of O. flavescens showed 2n = 64; NA = 66, with the largest chromosomes presenting acrocentric morphology, making such a result the main difference between the species. The analysis was able to detect two distinct groups, being the first one with karyotyped O. flavescens and the second with karyotyped O. nigripes. Identification afforded 211 loci, among them 181 (85.78%) polymorphic. The Jaccard similarity coefficient was in the range of 0.45 to 0.87. The UPGMA and Main Coordinate Analysis techniques demonstrated the existence of heterogeneous genetics among populations, but did not separate them completely in terms of geographical standards, and they are not influenced by the Uruguay River, which did not act as an efficient barrier.

Evidence for functional convergence in genes upregulated by herbivores ingesting plant secondary compounds.

BACKGROUND: Nearly 40 years ago, Freeland and Janzen predicted that liver biotransformation enzymes dictated diet selection by herbivores. Despite decades of research on model species and humans, little is known about the biotransformation mechanisms used by mammalian herbivores to metabolize plant secondary compounds (PSCs). We investigated the independent evolution of PSC biotransformation mechanisms by capitalizing on a dramatic diet change event-the dietary inclusion of creosote bush (Larrea tridentata)-that occurred in the recent evolutionary history of two species of woodrats (Neotoma lepida and N. bryanti). RESULTS: By comparing gene expression profiles of two populations of woodrats with evolutionary experience to creosote and one population naïve to creosote, we identified genes either induced by a diet containing creosote PSCs or constitutively higher in populations with evolutionary experience of creosote. Although only one detoxification gene (an aldo-keto reductase) was induced by both experienced populations, these populations converged upon functionally equivalent strategies to biotransform the PSCs of creosote bush by constitutively expressing aldehyde and alcohol dehydrogenases, Cytochromes P450s, methyltransferases, glutathione S-transferases and sulfotransferases. The response of the naïve woodrat population to creosote bush was indicative of extreme physiological stress. CONCLUSIONS: The hepatic detoxification system of mammals is notoriously complex, with hundreds of known biotransformation enzymes. The comparison herein of woodrat taxa that differ in evolutionary and ecological experience with toxins in creosote bush reveals convergence in the overall strategies used by independent species after a historical shift in diet. In addition, remarkably few genes seemed to be important in this dietary shift. The research lays the requisite groundwork for future studies of specific biotransformation pathways used by woodrats to metabolize the toxins in creosote and the evolution of diet switching in woodrats. On a larger level, this work advances our understanding of the mechanisms used by mammalian herbivores to process toxic diets and illustrates the importance of the selective relationship of PSCs in shaping herbivore diversity.

Comparison between Oligoryzomys nigripes and O. flavescens by RAPD and genetic diversity in O. nigripes (Rodentia, Cricetidae) / Comparação entre Oligoryzomys nigripes e O. flavescens e diversidade genética em O. nigripes (Rodentia, Cricetidae) por RAPD

The genus of Oligoryzomys includes species of small size, morphologically similar, which may impede taxonomic identification, mainly between O. flavescens (Waterhouse, 1837) and O. nigripes (Olfers, 1818). The main objective of this work was to investigate whether the RAPD markers are capable of genetically differentiating the specimens O. nigripes and O. flavescens, coming from Rio Grande do Sul (RS) and Santa Catarina (SC) states, and also to estimate the genetic variability among populations of O. nigripes, with the Uruguay River as a geographical barrier. For this purpose, samples were collected in fragments of forests situated in the North of RS, at FLONA (Floresta Nacional de Passo Fundo) and in fragments from SC, close to the Uruguay River. The karyotyping of two samples for each species was carried out and compared using the RAPD technique together with non- karyotyped individuals. Samples of O. nigripes presented 2n = 62; NA = 82, with submetacentric arms on the largest chromosomes, while samples of O. flavescens showed 2n = 64; NA = 66, with the largest chromosomes presenting acrocentric morphology, making such a result the main difference between the species. The analysis was able to detect two distinct groups, being the first one with karyotyped O. flavescens and the second with karyotyped O. nigripes. Identification afforded 211 loci, among them 181 (85.78%) polymorphic. The Jaccard similarity coefficient was in the range of 0.45 to 0.87. The UPGMA and Main Coordinate Analysis techniques demonstrated the existence of heterogeneous genetics among populations, but did not separate them completely in terms of geographical standards, and they are not influenced by the Uruguay River, which did not act as an efficient barrier.

O gênero Oligoryzomys inclui espécies de tamanho pequeno, morfologicamente semelhantes, com difícil identificação taxonômica, principalmente entre O. flavescens e O. nigripes. O objetivo principal deste trabalho foi investigar se os marcadores RAPD são capazes de diferenciar geneticamente as amostras de O. nigripes e O. flavescens, oriundas do Rio Grande do Sul (RS) e Santa Catarina (SC) e também para estimar o variabilidade genética entre populações de O. nigripes, tendo o rio Uruguai como uma barreira geográfica. Para este fim, as amostras foram coletadas em fragmentos florestais situados no Norte do RS, na FLONA (Floresta Nacional de Passo Fundo) e em fragmentos florestais de SC, próximos ao Rio Uruguai. O cariótipo de duas amostras de cada espécie foi realizado e comparado com a técnica RAPD em conjunto com indivíduos não cariotipados. As amostras de O. nigripes apresentaram 2n = 62, NA = 82, com braços submetacêntricos nos cromossomos maiores, enquanto que as amostras de O. flavescens mostraram 2n = 64, NA = 66, com os maiores cromossomos apresentando morfologia acrocêntrica, tornando tal resultado a principal diferença entre as espécies. As análises por RAPD foram capazes de detectar dois grupos distintos, sendo o primeiro com O.flavescens cariotipados e o segundo com O. nigripes cariotipados. Foram avaliados 211 loci, e entre eles 181 (85,78%) foram polimórficos. O coeficiente de similaridade de Jaccard variou de 0,45 a 0,87. A análise por UPGMA e análise de coordenadas principais demonstraram a existência de heterogeneidade genética entre as populações, mas não foi possível separá-las completamente em termos de padrões geográficos, e estas não são influenciadas pelo rio Uruguai, o qual não agiu como uma barreira eficiente.

A new species of swamp rat of the genus Scapteromys waterhouse, 1837 (Rodentia: Sigmodontinae) endemic to Araucaria angustifolia forest in Southern Brazil.

A new species of swamp rat of the genus Scapteromys from the Meridional Plateau of Southern Brazil is described. Morphological, molecular, and karyological analysis support the recognition of the new species, distinct from S. aquaticus and S. tumidus. Scapteromys sp. nov. is significantly smaller than the congeneric taxa considering most of the external and craniometric measurements and the pelage is conspicuously grayer and darker. It can be distinguished from S. tumidus by the laterally extended thenar pad of the manus and the parallel edges of the hamular process of the pterygoid, and from S. aquaticus by a grayer and darker pelage and smaller values of most external and craniometric measurements. Karyological analysis indicated a difference in chromosome numbers across the distributional range: 2n=34 and 2n=36. A total of 11 haplotypes were found along the range of the new species within the biogeographic province of Araucaria angustifolia Forest. Strongly supported substructure was found within the new taxon, resulting in two reciprocally monophyletic clades.

An integrative appraisal of the diversification in the Atlantic forest genus Delomys (Rodentia: Cricetidae: Sigmodontinae) with the description of a new species.

Recent taxonomic studies on Neotropical mammals have benefited from the use of genetic data to unravel and recognize species diversity in a number of genera, including the Atlantic forest endemic genus Delomys. However, the success of this approach depends on ability to link genetically identified lineages to species names based on voucher specimens that lack genetic data. Cytogenetic studies in the Atlantic forest endemic rodent genus Delomys have revealed two widespread karyotypes, 2n=72/FN=90 and 2n=82/FN=80, which have been respectively ascribed to Delomys sublineatus (Thomas, 1903) and D. dorsalis (Hensel, 1872). More recently, a third karyotype, 2n=82/FN=86, reported from specimens collected on two montaintops in southeastern Brazil, was interpreted as evidence for a third species, D. collinus Thomas, 1917. This nominal form had originally been described as a subspecies of D. dorsalis from Itatiaia, one of the mountain ranges where the third karyotype was later detected. The detection of two sympatric karyotypes at the type locality of D. collinus in the Itatiaia mountain range, Southeastern Brazil, prompted a reevaluation of the association of karyomorphs and species names. In this paper, we assessed the congruence of molecular (cytochrome b), cytogenetic and morphological characters, to diagnose the species in the genus, including data from recently collected series and type specimens. Our results indicate that the genetic and morphological patterns are largely congruent with the recognition of three species, each of which is karyotypically and morphologically diagnosable. Our morphological analyses of sympatric samples from Itatiaia refute the former association of the 2n=82/FN=86 karyotype with the holotype of D. dorsalis collinus (which is more similar to D. dorsalis with 2n=82/FN=80). Instead, we recognize and describe a new species for the 2n=82/FN=86 populations from the highest altitudinal zones of the Itatiaia and Caparaó mountains. The geographical variation in D. dorsalis is also explored and the status of D. d. collinus is discussed in the light of the molecular and morphological evidence. Finally, we discuss biogeographic hypotheses concerning the disjunct distributions of D. dorsalis and the new species.

Could hantavirus circulation superpose areas of highly endemic vaccinia virus outbreaks? A retrospective seroepidemiological study in State of Minas Gerais.

INTRODUCTION: Hantavirus infections have been described in several regions in Brazil through seroepidemiological studies. Usually, populations are associated with rural and wild environment mainly due to close contact to species of Sigmodontinae rodents, considered hantavirus reservoirs. METHODS: A retrospective serosurvey was conducted to access the hantavirus seroprevalence in people living in regions affected by bovine vaccinia outbreaks. RESULTS: Sera from 53 patients were analyzed and none of them presented anti-hantavirus IgG antibodies. CONCLUSIONS: This study presents an opportunity to analyze seronegativity despite close and recurrent contact with known hantavirus reservoirs. Aspects of hantavirus and bovine vaccinia emergence are also discussed.