RESUMO
Rodents of the genus Cerradomys belong to tribe Oryzomyini, one of the most diverse and speciose groups in Sigmodontinae (Rodentia, Cricetidae). The speciation process in Cerradomys is associated with chromosomal rearrangements and biogeographic dynamics in South America during the Pleistocene era. As the morphological, molecular and karyotypic aspects of Myomorpha rodents do not evolve at the same rate, we strategically employed karyotypic characters for the construction of chromosomal phylogeny to investigate whether phylogenetic relationships using chromosomal data corroborate the radiation of Cerradomys taxa recovered by molecular phylogeny. Comparative chromosome painting using Hylaeamys megacephalus (HME) whole chromosome probes in C. langguthi (CLA), Cerradomys scotii (CSC), C. subflavus (CSU) and C. vivoi (CVI) shows that karyotypic variability is due to 16 fusion events, 2 fission events, 10 pericentric inversions and 1 centromeric repositioning, plus amplification of constitutive heterochromatin in the short arms of the X chromosomes of CSC and CLA. The chromosomal phylogeny obtained by Maximum Parsimony analysis retrieved Cerradomys as a monophyletic group with 97% support (bootstrap), with CSC as the sister to the other species, followed by a ramification into two clades (69% of branch support), the first comprising CLA and the other branch including CVI and CSU. We integrated the chromosome painting analysis of Eumuroida rodents investigated by HME and Mus musculus (MMU) probes and identified several syntenic blocks shared among representatives of Cricetidae and Muridae. The Cerradomys genus underwent an extensive karyotypic evolutionary process, with multiple rearrangements that shaped extant karyotypes. The chromosomal phylogeny corroborates the phylogenetic relationships proposed by molecular analysis and indicates that karyotypic diversity is associated with species radiation. Three syntenic blocks were identified as part of the ancestral Eumuroida karyotype (AEK): MMU 7/19 (AEK 1), MMU 14 (AEK 10) and MMU 12 (AEK 11). Besides, MMU 5/10 (HME 18/2/24) and MMU 8/13 (HME 22/5/11) should be considered as signatures for Cricetidae, while MMU 5/9/14, 5/7/19, 5 and 8/17 for Sigmodontinae.
Assuntos
Roedores , Sigmodontinae , Animais , Sigmodontinae/genética , Roedores/genética , Filogenia , Arvicolinae , Muridae , Inversão Cromossômica , Coloração CromossômicaRESUMO
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.
Assuntos
Arvicolinae , Sigmodontinae , Animais , Ratos , Sigmodontinae/genética , Arvicolinae/genética , Áreas Alagadas , Sequências Repetitivas de Ácido Nucleico/genética , Cariótipo , DNA Satélite/genética , Elementos de DNA Transponíveis/genéticaRESUMO
We present the revalidation of the sigmodontinae rodent species R. emiliae, as well as the description of a new species for the genus Rhipidomys. The maximum likelihood analysis recovers R. emiliae as sister species of the clade with Rhipidomys sp. nov. and R. ipukensis, with high bootstrap values. Comparisons between these species based on the external, cranial, and dental morphology identified several unique characters in Rhipidomys sp. nov., including more grayish brown color of the dorsal coat, subsquamosal fenestra wide and long, angular process ends in the same position of the end of condyloid process, conspicuous protostyle and enterostyle. We describe a new karyotype (2n = 44 and FN = 64) for the genus and, based on an integrative analysis together with morphology and molecular phylogeny, assign it to R. emiliae, and assign the karyotype with 2n = 44 and FN = 52 to Rhipidomys sp. nov.. The analysis integrating data indicated that R. emiliae has a geographic distribution restricted to the lowlands of eastern Amazonia, whereas Rhipidomys sp. nov. occurs in the central Amazonia and Cerrado. The data showed that some Rhipidomys species have its distribution currently limited by rivers, as Rhipidomys sp. nov. occurring west of the Araguaia-Tocantins interfluve, R. emiliae east of the Tocantins River, and R. ipukensis between the Tocantins and Araguaia rivers. This work, in addition to revealing a still unknown biodiversity describing a species, brings a new understanding to the genus, and shows how integrating different markers helps in the correct association between the nominal form and the karyotype.
Assuntos
Arvicolinae , Roedores , Animais , Arvicolinae/genética , Brasil , Sigmodontinae/genética , Cariotipagem , FilogeniaRESUMO
X-autosome translocation (XY1Y2) has been reported in distinct groups of vertebrates suggesting that the rise of a multiple sex system within a species may act as a reproductive barrier and lead to speciation. The viability of this system has been linked with repetitive sequences located between sex and autosomal portions of the translocation. Herein, we investigate Oecomys auyantepui, using chromosome banding and Fluorescence In Situ Hybridization with telomeric and Hylaeamys megacephalus whole-chromosome probes, and phylogenetic reconstruction using mtDNA and nuDNA sequences. We describe an amended karyotype for O. auyantepui (2n = 64â65â/FNa = 84) and report for the first time a multiple sex system (XX/XY1Y2) in Oryzomyini rodents. Molecular data recovered O. auyantepui as a monophyletic taxon with high support and cytogenetic data indicate that O. auyantepui may exist in two lineages recognized by distinct sex systems. The Neo-X exhibits repetitive sequences located between sex and autosomal portions, which would act as a boundary between these two segments. The G-banding comparisons of the Neo-X chromosomes of other Sigmodontinae taxa revealed a similar banding pattern, suggesting that the autosomal segment in the Neo-X can be shared among the Sigmodontinae lineages with a XY1Y2 sex system.
Assuntos
Coloração Cromossômica , Sigmodontinae , Animais , Hibridização in Situ Fluorescente , Filogenia , Roedores/genética , Cromossomos Sexuais/genética , Sigmodontinae/genéticaRESUMO
Sigmodontine rodents (Cricetidae, Sigmodontinae) represent the second largest muroid subfamily and the most species-rich group of New World mammals, encompassing above 410 living species and ca. 87 genera. Even with advances on the clarification of sigmodontine phylogenetic relationships that have been made recently, the phylogenetic relationships among the 12 main groups of genera (i.e., tribes) remain poorly resolved, in particular among those forming the large clade Oryzomyalia. This pattern has been interpreted as consequence of a rapid radiation upon the group entrance into South America. Here, we attempted to resolve phylogenetic relationships within Sigmodontinae using target capture and high-throughput sequencing of ultraconserved elements (UCEs). We enriched and sequenced UCEs for 56 individuals and collected data from four already available genomes. Analyses of distinct data sets, based on the capture of 4634 loci, resulted in a highly resolved phylogeny consistent across different methods. Coalescent species-tree-based approaches, concatenated matrices, and Bayesian analyses recovered similar topologies that were congruent at the resolution of difficult nodes. We recovered good support for the intertribal relationships within Oryzomyalia; for instance, the tribe Oryzomyini appears as the sister taxa of the remaining oryzomyalid tribes. The estimates of divergence times agree with the results of previous studies. We inferred the crown age of the sigmodontine rodents at the end of the Middle Miocene, while the main lineages of Oryzomyalia appear to have radiated in a short interval during the Late Miocene. Thus, the collection of a genomic-scale data set with a wide taxonomic sampling provided resolution for the first time of the relationships among the main lineages of Sigmodontinae. We expect the phylogeny presented here will become the backbone for future systematic and evolutionary studies of the group.[Coalescent; Muroidea; Oryzomyalia; phylogenomics; polytomy; Rodentia; Sigmodontalia; species tree; UCEs.].
Assuntos
Roedores , Sigmodontinae , Animais , Arvicolinae , Teorema de Bayes , Filogenia , Sigmodontinae/genéticaRESUMO
Oryzomyini represents the most diverse and speciose tribe of subfamily Sigmodontinae, with 29 genera and about 141 species. This great diversity of species is distributed from southeastern North to southern South America. Its systematics have passed through major changes in the last years due to the integration of molecular data with morphological characters in phylogenetic inferences. Unsurprisingly, cytogenetic studies on Oryzomyini reflect such diversity, with chromosome diploid number varying from 2n = 16 to 2n = 88. In addition, some species present autosomal and sex chromosome polymorphisms, besides the presence of B chromosomes. However, despite decades of cytogenetic studies, our knowledge about the karyotype variability in this group were still poorly known. Considering such deep and profound changes on the tribe, along with important new evidence that was continuously being produced associated to field work in several areas of Brazil and South America, we performed a cytogenetic review of the Oryzomyini group. We provide standardized descriptions summarizing all the knowledge associated to the known species of the tribe. We also describe seven new karyotypes for the tribe, Euryoryzomys sp., 2n = 58 and FN = 92; Neacomys sp. 1, 2n = 48 and FN = 54; Neacomys sp. 2, 2n = 54 and FN = 62; Oecomys sp. 1, 2n = 54 and FN = 84; Oecomys sp. 2, 2n = 64 and FN = 92; Oecomys sp. 3, 2n = 84 and FN = 110; and Scolomys sp., 2n = 62 and FN = 80.
Assuntos
Arvicolinae , Sigmodontinae , Animais , Coloração Cromossômica , Cariótipo , Filogenia , Roedores , Sigmodontinae/genética , Especificidade da EspécieRESUMO
The genus Oecomys (Rodentia, Sigmodontinae) is distributed from southern Central America to southeastern Brazil in South America. It currently comprises 18 species, but multidisciplinary approaches such as karyotypic, morphological and molecular studies have shown that there is a greater diversity within some lineages than others. In particular, it has been proposed that O. paricola constitutes a species complex with three evolutionary units, which have been called the northern, eastern and western clades. Aiming to clarify the taxonomic status of O. paricola and determine the relevant chromosomal rearrangements, we investigated the karyotypes of samples from eastern Amazonia by chromosomal banding and FISH with Hylaeamys megacephalus (HME) whole-chromosome probes. We detected three cytotypes for O. paricola: A (OPA-A; 2n = 72, FN = 75), B (OPA-B; 2n = 70, FN = 75) and C (OPA-C; 2n = 70, FN = 72). Comparative chromosome painting showed that fusions/fissions, translocations and pericentric inversions or centromeric repositioning were responsible for the karyotypic divergence. We also detected exclusive chromosomal signatures that can be used as phylogenetic markers. Our analysis of karyotypic and distribution information indicates that OPA-A, OPA-B and OPA-C are three distinct species that belong to the eastern clade, with sympatry occurring between two of them, and that the "paricola group" is more diverse than was previously thought.
Assuntos
Variação Genética , Cariótipo , Sigmodontinae/genética , Animais , Cromossomos de Mamíferos/genética , Análise CitogenéticaRESUMO
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.
Assuntos
Cariótipo , Filogenia , Roedores/classificação , Roedores/genética , Animais , Evolução Biológica , Brasil , Coloração Cromossômica , Citogenética/métodos , Geografia , Cariotipagem , Masculino , Sigmodontinae/classificação , Sigmodontinae/genética , SinteniaRESUMO
BACKGROUND: The Neacomys genus is predominantly found in the Amazon region, and belongs to the most diverse tribe of the Sigmodontinae subfamily (Rodentia, Cricetidae, Oryzomyini). The systematics of this genus and questions about its diversity and range have been investigated by morphological, molecular (Cytb and COI sequences) and karyotype analysis (classic cytogenetics and chromosome painting), which have revealed candidate species and new distribution areas. Here we analyzed four species of Neacomys by chromosome painting with Hylaeamys megacephalus (HME) whole-chromosome probes, and compared the results with two previously studied Neacomys species and with other taxa from Oryzomyini and Akodontini tribes that have been hybridized with HME probes. Maximum Parsimony (MP) analyses were performed with the PAUP and T.N.T. software packages, using a non-additive (unordered) multi-state character matrix, based on chromosomal morphology, number and syntenic blocks. We also compared the chromosomal phylogeny obtained in this study with molecular topologies (Cytb and COI) that included eastern Amazonian species of Neacomys, to define the phylogenetic relationships of these taxa. RESULTS: The comparative chromosome painting analysis of the seven karyotypes of the six species of Neacomys shows that their diversity is due to 17 fusion/fission events and one translocation, pericentric inversions in four syntenic blocks, and constitutive heterochromatin (CH) amplification/deletion of six syntenic autosomal blocks plus the X chromosome. The chromosomal phylogeny is consistent with the molecular relationships of species of Neacomys. We describe new karyotypes and expand the distribution area for species from eastern Amazonia and detect complex rearrangements by chromosome painting among the karyotypes. CONCLUSIONS: Our phylogeny reflects the molecular relationships of the Akodontini and Oryzomyini taxa and supports the monophyly of Neacomys. This work presents new insights about the chromosomal evolution of this group, and we conclude that the karyotypic divergence is in accord with phylogenetic relationships.
Assuntos
Coloração Cromossômica , Cromossomos de Mamíferos/genética , Filogenia , Sigmodontinae/genética , Animais , Brasil , Sondas de DNA , Geografia , Cariótipo , SinteniaRESUMO
The nominal species Calomys tener (Winge, 1887) ranges broadly in open lands of the Caatinga, Cerrado, Pantanal and Mata Atlântica of Brazil, and was recently reported from the Pampas of southern Brazil, and in the Selva Paranaense of eastern Paraguay and northeastern Argentina. This rodent can be infected with the pathogenic Araraquara hantavirus in Brazil. Given that most epidemiological studies have not taken into account updated taxonomic findings of their rodent hosts, in this study, we obtained sequence data of the Cyt-b and COI genes of specimens of C. tener from 22 different geographical localities from throughout the currently known distribution of the species (including individuals from Argentina, Paraguay, Bolivia, and Brazil) to test if it constitutes a single genetic unit or if it presents genetic discontinuities that may represent different evolutionary lineages. Phylogenetic analyses including several species of Calomys recovered several clades with strong support. Regarding C. tener, it is recovered as sister to the node that cluster C. laucha (Fischer, 1814) sensu lato, C. expulsus (Lund, 1841) and species in the C. callosus (Rengger, 1830) species complex. At the intraspecific level there are no genetic gaps among haplotypes of C. tener that could suggest more than one species. The recent captures in the Pampas of southern Brazil and in the Selva Paranaense suggest that the species may be colonizing new geographic areas.(AU)