Dentes supranumerários em Necromys lasiurus (Rodentia, Cricetidae): primeiro registro em Sigmodontinae

There are several kinds of anomalies related to the teeth reported in mammals, and one of them is known as supernumerary teeth and is commonly noticed in the literature, being reported in nearly all orders of mammals. Here, we report the occurrence of supernumerary molars in the sigmodontine rodent Necromys lasiurus, a common and widespread small rodent of tribe Akodontini. In order to assess the patterns of morphometric variation of N. lasiurus in eastern South America, we examined the skulls of 1763 specimens. The supernumerary molars were found in 2 individuals, which represent a frequency of 0.11%. The origin of supernumerary teeth started a long discussion on tooth homology, whether this anomaly is a result of heredity, a mutation or an atavism. Based on the morphologies presented by the extra teeth encountered in N. lasiurus and on the evidences and hypothesis available in the literature, we consider that the presence of these supernumerary molars in one of the studied animals could be considered an atavism, and we also consider the extra molar presented by the other specimen is a malformation, due to some kind of random process occurred in later stages of the development of distal dental gem. To the best of our knowledge, this represents the first record of supernumerary molars in the subfamily Sigmodontinae and one of the few known cases in rodents.Diversos tipos de anomalias dentárias já foram descritas para mamíferos e uma delas é conhecida como dente supranumerário comumente reportada na literatura para quase todas as ordens de mamíferos. No presente trabalho apresentamos a ocorrência de molares extras em Necromys lasiurus, uma espécie de pequeno roedor sigmodontíneo comum e amplamente distribuído, membro da tribo Akodontini. Durante o levantamento de dados para avaliação morfométrica da variação da espécie no leste da América do Sul, foram examinados os crânios de 1763 espécimes. Os dentes supranumerários foram encontrados em dois indivíduos, representando 0.11% da amostra investigada. A ocorrência dos dentes supranumerários há muito tempo levanta questões acerca da homologia dentária, das mutações e dos atavismos que podem estar relacionados à origem desta anomalia. Baseados na morfologia apresentada pelos molares extra numerários de N. lasiurus, nós consideramos que a presença dos mesmos em um dos espécimes é um atavismo, e no outro, trata-se de uma malformação devido a um processo de origem tardia no desenvolvimento das gemas dentárias. Com base em nosso conhecimento de outras espécies e em toda a revisão bibliográfica, a ocorrência dos dentes supranumerários em N. lasiurus trata-se dos primeiros registros da anomalia para a subfamília Sigmodontinae e um dos poucos já registrados para a ordem Rodentia.Fil: Simoes Libardi, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidade Do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz Esalq; BrasilFil: Reis Percequillo, Alexandre. Universidade Do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz Esalq; Brasi

Geographic distribution of the genera of the Tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae) in South America: patterns of distribution and diversity

The Oryzomyini is the most diverse tribe of the sigmodontine (Cricetidae: Sigmodontinae) radiation, including 28 genera and about 130 species, with this diversity reflected in the ecological and morphological variation observed among members. There are many hypotheses to explain the emergence and diversification of the Sigmodontinae in South America, including areas of original differentiation (AOD). In this paper we provide information on the geographic distribution of all extant genera in the tribe Oryzomyini, organizing these data in a gazetteer that includes provenance (collection locality, state or province, country), elevation, and geographical coordenates. Distribution maps generated for all genera and species then serve as the starting point for testing patterns of geographic distribution and diversity, and especially the AOD hypothesis advocating origination in the northern Andes. Our results reveal considerable generic and specific richness and show that there are three general patterns of distribution, the Trans-Andean, Andean, and Cis-Andean. Moreover, different genera encompass distributions that are endemic, disjunct, or widely distributed, as well as those restricted by habitats in both forest and open areas. Recent phylogenetic hypotheses indicate that the distribution patterns of oryzomyines do not correlate with the major lineages of the inclusive clades; rather, each main lineage displays most of the biogeographic patterns described for the tribe as a whole. The northern Andes cannot be considered as AOD, since the most records for Oryzomyini are located in the Cis-Andes area. The northern Andes is the second region in number of species, while the Trans-Andean represents the third richest region in South America. Patterns of richness of the tribe are strongly concordant with several of the centers or regions of endemism described in the literature. Areas of high richness are located mainly in the Andes, followed in lesser degree by areas in the Guyanan Shield, Brazilian Atlantic and Amazon Forests, and Paraguayan Chaco

Age and habitat quality matters: isotopic variation of two sympatric species of rodents in Neotropical Forest

Dietary studies allow us to understand important ecological patterns such as intra- and interpopulation variation and interspecific differences regarding the use of food sources. Stable isotopes have been successfully employed to detect dietary differences between species and feeding shifts within a species, as a response to age, habitat use, and resource availability. Here we investigated the stable isotope compositions of carbon and nitrogen of young and adult specimens of Euryoryzomys russatus and Sooretamys angouya and their stomach contents, in a complex mosaic of vegetation in the Brazilian Atlantic Forest. Isotopes indicated a pronounced inter- and intraspecific plasticity in resource use for E. russatus and S. angouya. Plant sources were the prevalent feeding items for E. russatus, with low to intermediate consumption of arthropods. For S. angouya, plants were dominant in the stomach content, but arthropod arose as an important source. E. russatus showed more variation in isotopic signature between grids than S. angouya, suggesting that the former was more affected by habitat changes. These results allow us to better understand the ontogeny, diet and the behavioral responses to environmental variations of both species. Finally, our study contributes to reduce the lack of knowledge about sympatric species ecology and aggregates information for their conservation.Fil: Bovendorp, Ricardo Siqueira. Universidade Do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; Brasil. Universidade Estadual Paulista “Júlio de Mesquita Filho”; BrasilFil: Simoes Libardi, Gustavo. Universidade Do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Diversidad y Evolución Austral; ArgentinaFil: Sarmento, Mariana Montagner de Moraes. Universidade Do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; BrasilFil: Camargo, Plínio Barbosa. Universidade de Sao Paulo; BrasilFil: Reis Percequillo, Alexandre. Universidade Do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; Brasi

Small mammals of the Estação Ecológica de Bananal, southeastern Atlantic Forest, Brazil, with description of a new species of Brucepattersonius (Rodentia, Sigmodontinae)

The Atlantic Forest harbors an impressive diversity of nonvolant small mammals. Despite having been the target of many ecological and taxonomical studies in the last decades, this group is still poorly known in several aspects – basic information on intrapopulational morphologic variation and proper diagnoses are lacking for many species, even for common taxa. This is related to the fact that large series of specimens from a single locality are extremely rare in scientific collections. A consistent sampling effort was conducted at Estação Ecológica de Bananal, northeastern São Paulo State, throughout seven field expeditions between 2003 and 2011, under the coordination of the Museu de Zoologia da Universidade de São Paulo, resulting in extensive series of nonvolant small mammals. We studied in detail the external and cranio-dental morphology of this sample (575 specimens), that we assigned to 31 known species besides one new species to science. Most species belong to order Rodentia (26 species) from the families Cricetidae (22 species) and Echimyidae (four species); the remaining (six species) are marsupials from the order Didelphimorphia, family Didelphidae. This is one of the most diverse assemblages ever recorded in this biome, and includes some of the rarest endemic rodents of the Atlantic Forest, such as Abrawayaomys ruschii, Blarinomys breviceps, Drymoreomys albimaculatus, Phaenomys ferrugineus, Phyllomys kerri and Rhagomys rufescens. This outstanding richness can be explained by the extensive sampling effort performed for a long period of time. Also, the capture success of the third expedition (8.25%) is among the highest rates obtained in the Atlantic Forest and the extensive use of pitfall traps was fundamental for trapping this high number of species. Herein, we provide an annotated list of nonvolant small mammals occurring at Estação Ecológica de Bananal, with comprehensive analyses of morphological variation and detailed diagnoses that will allow their proper identification, and will provide a sound basis for a better comprehension of the geographic variation of these taxa across the biome. We also present a formal description for a new species of Brucepattersonius from the mountain ranges along the Paraíba do Sul valley. For five species of sigmodontine rodents, we investigate the levels of ontogenetic and sexual variation, and while the first is accentuate in all analyzed species the second does not contribute significantly to intrapopulation variation

Novo gênero para Loncheres grandis Wagner, 1845, com comentários taxonômicos sobre outros equimídeos arborícolas (Rodentia, Echimyidae)

A study of arboreal echimyids in Brazilian and European collections revealed a number of morphological traits supporting the recognition of Loncheres grandis Wagner, 1845, currently included in Makalata Husson, 1978, as a full genus. Our proposition of a new genus for L. grandis changed the species content of Makalata, what led us to reformulate the generic diagnosis for this genus and other arboreal echimyids as well. The new genus can be distinguished by several external characters including its color pattern, striking differences in tail pilosity, and palmar and plantar pad morphology. Osteological distinguishing traits includes the shape of nasals, the structure of the postorbital process of the zygomatic arch, petrosal morphology, the presence of a posterior maxillary foramen, the crown pattern of molariform teeth, and baculum morphology.O estudo de equimídeos arbóreos em coleções brasileiras e européias revelou diversas características morfológicas sustentando o reconhecimento de Loncheres grandis Wagner, 1845, atualmente incluído em Makalata Husson, 1978, como um gênero válido. Nossa proposta de um novo gênero para L. grandis alterou o conteúdo específico de Makalata, o que nos levou a reformular a diagnose genérica para este gênero, assim como para outros equimídeos arbóreos. O novo gênero pode ser distinguido através de várias características externas tais como seu padrão de coloração, uma notável distinção da pilosidade caudal e a morfologia das almofadas das patas anteriores e posteriores. Características osteológicas distintivas incluem a forma dos nasais, a estrutura do processo pós-orbital do arco zigomático, a morfologia do petroso, a presença de um foramen maxilar posterior, a morfologia da coroa dos dentes molariformes e a forma do báculo

Mammalia, Rodentia, Echimyidae, Phyllomys blainvilii (Jourdan, 1837): range extension and new geographic distribution map

Non

Similar but different: Revealing the relative roles of species‐traits versus biome properties structuring genetic variation in South American marsh rats

AimWetland habitats, and the ecological restrictions imposed by them, structure patterns of genetic variation in constituent taxa. As such, genetic variation may reflect properties of the specific biomes species inhabit, or shared life history traits among species may result in similar genetic structure. We evaluated these hypotheses jointly by quantifying the similarity of genetic structure in three South American marsh rat species (Holochilus), and test how genetic variation in each species relates to biome‐specific environmental space and historical stability.LocationSouth America.TaxonRodentia.MethodsUsing complementary analyses (Mantel tests, dbRDA, Procrustes, covariance structure of allele frequencies and environmental niche models [ENMs]) with 8,000–32,000 SNPs per species, we quantified the association between genomic variation and geographic and/or environmental differences.ResultsSignificant association between genetic variation and geography was identified for all species. Similarity in the strength of the association suggests connectivity patterns dictated by shared species‐traits predominate at the biome scale. However, substantial amounts of genetic variation are not explained by geography. Focusing on this portion of the variance, we demonstrate a significant quantitative association between genetic variation and the environmental space of a biome, and a qualitative association with varying regional stability. Specifically, historically stable areas estimated from ecological niche models are correlated with local levels of geographic structuring, suggesting that local biome‐specific histories affect population isolation/connectivity.Main conclusionsThese tests show that although species exhibit similar patterns of genetic variation that are consistent with shared natural histories, irrespective of inhabiting different wetland biomes, local biome‐specific properties (i.e. varying environmental conditions and historical stability) contribute to departures from equilibrium patterns of genetic variation expected by isolation by geographic distance. The reflection of these biome‐specific properties in the genetic structure of the marsh rats provides a window into the differences among South American wetlands with evolutionary consequences for their respective constituent assemblages.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149336/1/jbi13529.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149336/2/jbi13529_am.pd

A new genus of oryzomyine rodents (Cricetidae, Sigmodontinae) with three new species from montane cloud forests, western Andean cordillera of Colombia and Ecuador

The Andean cloud forests of western Colombia and Ecuador are home to several endemic mammals; members of the Oryzomyini, the largest Sigmodontinae tribe, are extensively represented in the region. However, our knowledge about this diversity is still incomplete, as evidenced by several new taxa that have been described in recent years. Extensive field work in two protected areas enclosing remnants of Chocó montane forest recovered a high diversity of small mammals. Among them, a medium-sized oryzomyine is here described as a new genus having at least three new species, two of them are named and diagnosed. Although externally similar to members of the genera Nephelomys and Tanyuromys, the new genus has a unique molar pattern within the tribe, being characterized by a noticeable degree of hypsodonty, simplification, lamination, and third molar compression. A phylogeny based on a combination of molecular markers, including nuclear and mitochondrial genes, and morphological data recovered the new genus as sister to Mindomys, and sequentially to Nephelomys. The new genus seems to be another example of a sigmodontine rodent unique to the Chocó biogeographic region. Its type species inhabits cloud forest between 1,600 and 2,300 m in northernmost Ecuador (Carchi Province); a second species is restricted to lower montane forest, 1,200 m, in northern Ecuador (Imbabura Province); a third putative species, here highlighted exclusively by molecular evidence from one immature specimen, is recorded in the montane forest of Reserva Otonga, northern Ecuador (Cotopaxi Province). Finally, the new genus is also recorded in southernmost Colombia (Nariño Department), probably represented there also by a new species. These species are spatially separated by deep river canyons through Andean forests, resulting in marked environmental discontinuities. Unfortunately, Colombian and Ecuadorian Pacific cloud forests are under rapid anthropic transformation. Although the populations of the type species are moderately abundant and occur in protected areas, the other two persist in threatened forest fragments.Fil: Brito, Jorge. Instituto Nacional de Biodiversidad; EcuadorFil: Koch, Claudia. Zoologisches Forschungsmuseum Alexander Koenig.; AlemaniaFil: Reis Percequillo, Alexandre. Universidade do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; BrasilFil: Tinoco, Nicolás. Pontificia Universidad Católica del Ecuador; EcuadorFil: Weksler, Marcelo. Universidade Federal do Rio de Janeiro; BrasilFil: Pinto, C. Miguel. Observatorio de Biodiversidad Ambiente y Salud; EcuadorFil: Pardiñas, Ulises Francisco J.. Instituto Nacional de Biodiversidad; Ecuador. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Diversidad y Evolución Austral; Argentin

Geographic variation in a South American clade of mormoopid bats, Pteronotus (Phyllodia), with description of a new species

The subgenus Phyllodia (genus Pteronotus) comprises 9 species ranging from the western coast of Mexico to central Brazil, including Greater and Lesser Antilles. Two of them, Pteronotus rubiginosus and Pteronotus sp. 1, form an endemic South American clade within Phyllodia and are reported in sympatry for several localities in Guyana, Suriname, French Guiana, and northern Brazil. We herein performed a comprehensive investigation to fully characterize the cranial variation and genetic intraspecific structuring within this clade. We also integrated genetic, morphological, and acoustic evidence to formally describe the species previously reported as Pteronotus sp. 1. Specimens of P. rubiginosus occurring in sympatry with the new species have a more distinctive cranial phenotype than those from allopatric areas, suggesting character displacement as a potential force promoting divergence by decreasing resource competition or reproductive interactions between them. Although the 2 species are sympatric in several localities, the divergence in their echolocation calls also may be promoting resource partitioning at the microhabitat level, with P. rubiginosus foraging in less cluttered areas and the new species restricted to more cluttered areas. © 2018 American Society of Mammalogists, www.mammalogy.org