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Ruiz-García M, Pinilla-Beltrán D, Murillo-García OE, Pinto CM, Brito J, Shostell JM. Comparative mitogenome phylogeography of two anteater genera ( Tamandua and Myrmecophaga; Myrmecophagidae, Xenarthra): Evidence of discrepant evolutionary traits. Zool Res 2021; 42:525-547. [PMID: 34313411 PMCID: PMC8455474 DOI: 10.24272/j.issn.2095-8137.2020.365] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 07/23/2021] [Indexed: 11/07/2022] Open
Abstract
The species within Xenarthra (sloths, anteaters, and armadillos) are quintessential South American mammals. Of the three groups, Vermilingua (anteaters) contains the fewest extant and paleontological species. Here, we sampled and sequenced the entire mitochondrial genomes (mitogenomes) of two Tamandua species (Tamandua tetradactyla and Tamandua mexicana) (n=74) from Central and South America, as well as Myrmecophaga tridactyla (n=41) from South America. Within Tamandua, we detected three different haplogroups. The oldest (THI) contained many specimens with the T. tetradactyla morphotype (but also several with the T. mexicana morphotype) and originated in southeastern South America (currently Uruguay) before moving towards northern South America, where the THII haplogroup originated. THII primarily contained specimens with the T. mexicana morphotype (but also several with the T. tetradactyla morphotype) and was distributed in Central America, Colombia, and Ecuador. THI and THII yielded a genetic distance of 4%. THII originated in either northern South America or "in situ" in Central America with haplogroup THIII, which consisted of ~50% T. mexicana and 50% T. tetradactyla phenotypes. THIII was mostly located in the same areas as THII, i.e., Central America, Ecuador, and Colombia, though mainly in the latter. The three haplogroups overlapped in Colombia and Ecuador. Thus, T. tetradactyla and T. mexicana were not reciprocally monophyletic. For this reason, we considered that a unique species of Tamandua likely exists, i.e., T. tetradactyla. In contrast to Tamandua, M. tridactyla did not show different morphotypes throughout its geographical range in the Neotropics. However, two very divergent genetic haplogroups (MHI and MHII), with a genetic distance of ~10%, were detected. The basal haplogroup, MHI, originated in northwestern South America, whereas the more geographically derived haplogroup, MHII, overlapped with MHI, but also expanded into central and southern South America. Thus, Tamandua migrated from south to north whereas Myrmecophaga migrated from north to south. Our results also showed that temporal mitochondrial diversification for Tamandua began during the Late Pliocene and Upper Pleistocene, but for Myrmecophaga began during the Late Miocene. Furthermore, both taxa showed elevated levels of mitochondrial genetic diversity. Tamandua showed more evidence of female population expansion than Myrmecophaga. Tamandua experienced population expansion ~0.6-0.17 million years ago (Mya), whereas Myrmecophaga showed possible population expansion ~0.3-0.2 Mya. However, both taxa experienced a conspicuous female decline in the last 10 000-20 000 years. Our results also showed little spatial genetic structure for both taxa. However, several analyses revealed higher spatial structure in Tamandua than in Myrmecophaga. Therefore, Tamandua and Myrmecophaga were not subjected to the same biogeographical, geological, or climatological events in shaping their genetic structures.
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Affiliation(s)
- Manuel Ruiz-García
- Laboratorio de Genética de Poblaciones Molecular-Biología Evolutiva, Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá DC 110231, Colombia. E-mail:
| | - Daniel Pinilla-Beltrán
- Laboratorio de Genética de Poblaciones Molecular-Biología Evolutiva, Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá DC 110231, Colombia
| | - Oscar E Murillo-García
- Grupo de Investigación en Ecología Animal, Departamento de Biología, Facultad de Ciencias Naturales y Exactas, Universidad del Valle, Apartado Aéreo, Cali 25360, Colombia
| | | | - Jorge Brito
- Instituto Nacional de Biodiversidad (INABIO), Quito 170135, Ecuador
| | - Joseph Mark Shostell
- Math, Science and Technology Department, University of Minnesota Crookston, Crookston, MN 56716, USA
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Ruiz-garcía M, Chacón D, Plese T, Shostell JM. Molecular Phylogenetics of Bradypus (Three-Toed Sloth, Pilosa: Bradypodidae, Mammalia) and Phylogeography of Bradypus variegatus (Brown-Throated Three-Toed Sloth) with Mitochondrial Gene Sequences. J MAMM EVOL 2020; 27:461-82. [DOI: 10.1007/s10914-019-09465-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Varela L, Tambusso PS, McDonald HG, Fariña RA. Phylogeny, Macroevolutionary Trends and Historical Biogeography of Sloths: Insights From a Bayesian Morphological Clock Analysis. Syst Biol 2018; 68:204-218. [DOI: 10.1093/sysbio/syy058] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 09/10/2018] [Indexed: 11/14/2022] Open
Affiliation(s)
- Luciano Varela
- Departamento de Paleontología, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
| | - P Sebastián Tambusso
- Departamento de Paleontología, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
| | - H Gregory McDonald
- Bureau of Land Management, Utah State Office, 440 West 200 South, Salt Lake City, UT 84101 USA
| | - Richard A Fariña
- Departamento de Paleontología, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
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Casali DM, Martins-santos E, Santos ALQ, Miranda FR, Mahecha GAB, Perini FA. Morphology of the tongue of Vermilingua (Xenarthra: Pilosa) and evolutionary considerations: CASALI et al. J Morphol 2017; 278:1380-99. [DOI: 10.1002/jmor.20718] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Ruiz-García M, Chacón D, Plese T, Schuler I, Shostell JM. Mitogenomics phylogenetic relationships of the current sloth's genera and species (Bradypodidae and Megalonychidae). Mitochondrial DNA A DNA Mapp Seq Anal 2017; 29:281-299. [PMID: 28129732 DOI: 10.1080/24701394.2016.1275602] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We sequenced the complete mitogenome of 39 sloths (19 Bradypus variegatus, 4 B. tridactylus, 1 B. pygmaeus, 1 B. torquatus, 4 Choloepus didactylus, and 10 C. hoffmanni). A Bayesian tree (BI) indicated a temporal split between Bradypus and Choloepus around 31 million years ago (MYA, Oligocene) and the other major splits within each genera during the Miocene and Pliocene. A haplotype network (MJN) estimated a lower temporal split between the sloth genera (around 23.5 MYA). Both methods detected the ancestor of B. torquatus as the first to diverge within Bradypus (21 for BI and 19 MJN), followed by that of the ancestor of B. tridactylus. The split of B. pygmaeus from the common ancestor with B. variegatus was around 12 MYA (BI) or 4.3 MYA (MJN). The splits among the previous populations of B. variegatus began around 8 MYA (BI) or 3.6 MYA (MJN). The trans-Andean population was the first to diverge from the remaining cis-Andean populations of B. variegatus. The genetic differentiation of the trans-Andean B. variegatus population relative to the cis-Andean B. variegatus is similar to that found for different species of sloths. The mitogenomic analysis resolved the differentiation of C. hoffmanni from the C. didactylus individuals of the Guiana Shield. However, one C. didactylus from the Colombian Amazon specimen was inside the C. hoffmanni clade. This could be the first example of possible natural hybridization in the Amazon of both Choloepus taxa or the existence of un-differentiable phenotypes of these two species in some Amazonian areas.
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Affiliation(s)
- Manuel Ruiz-García
- a Departamento de Biología, Facultad de Ciencias , Pontificia Universidad Javeriana , Bogotá , DC , Colombia
| | - Diego Chacón
- a Departamento de Biología, Facultad de Ciencias , Pontificia Universidad Javeriana , Bogotá , DC , Colombia
| | | | - Ingrid Schuler
- a Departamento de Biología, Facultad de Ciencias , Pontificia Universidad Javeriana , Bogotá , DC , Colombia
| | - Joseph Mark Shostell
- c Math, Science and Technology Department , University of Minnesota Crookston , Crookston , MN , USA
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Gibb GC, Condamine FL, Kuch M, Enk J, Moraes-Barros N, Superina M, Poinar HN, Delsuc F. Shotgun Mitogenomics Provides a Reference Phylogenetic Framework and Timescale for Living Xenarthrans. Mol Biol Evol 2015; 33:621-42. [PMID: 26556496 PMCID: PMC4760074 DOI: 10.1093/molbev/msv250] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Xenarthra (armadillos, sloths, and anteaters) constitutes one of the four major clades of placental mammals. Despite their phylogenetic distinctiveness in mammals, a reference phylogeny is still lacking for the 31 described species. Here we used Illumina shotgun sequencing to assemble 33 new complete mitochondrial genomes, establishing Xenarthra as the first major placental clade to be fully sequenced at the species level for mitogenomes. The resulting data set allowed the reconstruction of a robust phylogenetic framework and timescale that are consistent with previous studies conducted at the genus level using nuclear genes. Incorporating the full species diversity of extant xenarthrans points to a number of inconsistencies in xenarthran systematics and species definition. We propose to split armadillos into two distinct families Dasypodidae (dasypodines) and Chlamyphoridae (euphractines, chlamyphorines, and tolypeutines) to better reflect their ancient divergence, estimated around 42 Ma. Species delimitation within long-nosed armadillos (genus Dasypus) appeared more complex than anticipated, with the discovery of a divergent lineage in French Guiana. Diversification analyses showed Xenarthra to be an ancient clade with a constant diversification rate through time with a species turnover driven by high but constant extinction. We also detected a significant negative correlation between speciation rate and past temperature fluctuations with an increase in speciation rate corresponding to the general cooling observed during the last 15 My. Biogeographic reconstructions identified the tropical rainforest biome of Amazonia and the Guiana Shield as the cradle of xenarthran evolutionary history with subsequent dispersions into more open and dry habitats.
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Affiliation(s)
- Gillian C Gibb
- Institut des Sciences de l'Evolution, UMR 5554, CNRS, IRD, EPHE, Université de Montpellier, Montpellier, France Ecology Group, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Fabien L Condamine
- Institut des Sciences de l'Evolution, UMR 5554, CNRS, IRD, EPHE, Université de Montpellier, Montpellier, France Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden Department of Biological Sciences, University of Alberta, Edmonton, AL, Canada
| | - Melanie Kuch
- McMaster Ancient DNA Centre, Department of Anthropology and Biology, McMaster University, Hamilton, ON, Canada
| | - Jacob Enk
- McMaster Ancient DNA Centre, Department of Anthropology and Biology, McMaster University, Hamilton, ON, Canada
| | - Nadia Moraes-Barros
- Cibio/Inbio, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Vairão, Portugal Laboratório de Biologia Evolutiva e Conservação de Vertebrados (Labec), Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Mariella Superina
- Laboratorio de Endocrinología de la Fauna Silvestre, IMBECU, CCT CONICET Mendoza, Mendoza, Argentina
| | - Hendrik N Poinar
- McMaster Ancient DNA Centre, Department of Anthropology and Biology, McMaster University, Hamilton, ON, Canada
| | - Frédéric Delsuc
- Institut des Sciences de l'Evolution, UMR 5554, CNRS, IRD, EPHE, Université de Montpellier, Montpellier, France
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Buckley M, Fariña RA, Lawless C, Tambusso PS, Varela L, Carlini AA, Powell JE, Martinez JG. Collagen Sequence Analysis of the Extinct Giant Ground Sloths Lestodon and Megatherium. PLoS One 2015; 10:e0139611. [PMID: 26540101 PMCID: PMC4634953 DOI: 10.1371/journal.pone.0139611] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 09/14/2015] [Indexed: 11/19/2022] Open
Abstract
For over 200 years, fossils of bizarre extinct creatures have been described from the Americas that have ranged from giant ground sloths to the ‘native’ South American ungulates, groups of mammals that evolved in relative isolation on South America. Ground sloths belong to the South American xenarthrans, a group with modern although morphologically and ecologically very different representatives (anteaters, armadillos and sloths), which has been proposed to be one of the four main eutherian clades. Recently, proteomics analyses of bone collagen have recently been used to yield a molecular phylogeny for a range of mammals including the unusual ‘Malagasy aardvark’ shown to be most closely related to the afrotherian tenrecs, and the south American ungulates supporting their morphological association with condylarths. However, proteomics results generate partial sequence information that could impact upon the phylogenetic placement that has not been appropriately tested. For comparison, this paper examines the phylogenetic potential of proteomics-based sequencing through the analysis of collagen extracted from two extinct giant ground sloths, Lestodon and Megatherium. The ground sloths were placed as sister taxa to extant sloths, but with a closer relationship between Lestodon and the extant sloths than the basal Megatherium. These results highlight that proteomics methods could yield plausible phylogenies that share similarities with other methods, but have the potential to be more useful in fossils beyond the limits of ancient DNA survival.
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Affiliation(s)
- Michael Buckley
- Faculty of Life Sciences, Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester, United Kingdom
- * E-mail:
| | - Richard A. Fariña
- Sección Paleontología, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo, Uruguay
| | - Craig Lawless
- Michael Smith Building, The University of Manchester, Manchester, United Kingdom
| | - P. Sebastián Tambusso
- Sección Paleontología, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo, Uruguay
| | - Luciano Varela
- Sección Paleontología, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo, Uruguay
| | - Alfredo A. Carlini
- Facultad de Ciencias Naturales y Museo, Museo de La Plata, Buenos Aires, Argentina
| | - Jaime E. Powell
- Facultad de Ciencias Naturales, Universidad Nacional de Tucumán, Tucumán Province, Argentina
| | - Jorge G. Martinez
- Instituto Superior de Estudios Sociales-CONICET, Instituto de Arqueología y Museo-UNT, Tucumán Province, Argentina
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Abstract
The Magnaorder Xenarthra is one of the four main supraordinal eutherian clades, together with Afrotheria, Euarchontoglires and Laurasiatheria. Xenarthra is an eminently Central and South American group of special interest in phylogenetic studies due to its possible position at the base of the eutherian tree. The use of modern cytogenetic techniques in some species of Xenarthra has provided important insights into the karyotypic evolution of mammals. Nevertheless, chromosome analyses in the group are still restricted, with only a few individuals of each species studied and karyotype descriptions mostly without banding patterns. In addition, it is likely that still unknown species exist and that the chromosome variability in the group is underestimated. We present a review of the currently available data on Xenarthra chromosomes and genomes and on the impact that their study has had in the understanding of mammalian genome evolution. It is clear that further cytogenetic analyses in Xenarthra, including banding patterns and molecular approaches, are likely to help in the identification of new species, reveal still undetected chromosome variations, provide information to support conservation strategies planning, and greatly contribute to a better understanding of mammalian genome evolution.
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Affiliation(s)
- M Svartman
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
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Azevedo NF, Svartman M, Manchester A, de Moraes-Barros N, Stanyon R, Vianna-Morgante AM. Chromosome painting in three-toed sloths: a cytogenetic signature and ancestral karyotype for Xenarthra. BMC Evol Biol 2012; 12:36. [PMID: 22429690 PMCID: PMC3383463 DOI: 10.1186/1471-2148-12-36] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2011] [Accepted: 03/19/2012] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Xenarthra (sloths, armadillos and anteaters) represent one of four currently recognized Eutherian mammal supraorders. Some phylogenomic studies point to the possibility of Xenarthra being at the base of the Eutherian tree, together or not with the supraorder Afrotheria. We performed painting with human autosomes and X-chromosome specific probes on metaphases of two three-toed sloths: Bradypus torquatus and B. variegatus. These species represent the fourth of the five extant Xenarthra families to be studied with this approach. RESULTS Eleven human chromosomes were conserved as one block in both B. torquatus and B. variegatus: (HSA 5, 6, 9, 11, 13, 14, 15, 17, 18, 20, 21 and the X chromosome). B. torquatus, three additional human chromosomes were conserved intact (HSA 1, 3 and 4). The remaining human chromosomes were represented by two or three segments on each sloth. Seven associations between human chromosomes were detected in the karyotypes of both B. torquatus and B. variegatus: HSA 3/21, 4/8, 7/10, 7/16, 12/22, 14/15 and 17/19. The ancestral Eutherian association 16/19 was not detected in the Bradypus species. CONCLUSIONS Our results together with previous reports enabled us to propose a hypothetical ancestral Xenarthran karyotype with 48 chromosomes that would differ from the proposed ancestral Eutherian karyotype by the presence of the association HSA 7/10 and by the split of HSA 8 into three blocks, instead of the two found in the Eutherian ancestor. These same chromosome features point to the monophyly of Xenarthra, making this the second supraorder of placental mammals to have a chromosome signature supporting its monophyly.
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Affiliation(s)
- Nathália F Azevedo
- Departamento de Genética e Biologia Evolutiva, Universidade de São Paulo, Cidade Universitária, São Paulo, Brazil
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de Moraes-Barros N, Silva JAB, Morgante JS. Morphology, molecular phylogeny, and taxonomic inconsistencies in the study ofBradypussloths (Pilosa: Bradypodidae). J Mammal 2011. [DOI: 10.1644/10-mamm-a-086.1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Barros MC, Sampaio I, Schneider H, Langguth A. Molecular phylogenies, chromosomes and dispersion in Brazilian akodontines (Rodentia, Sigmodontinae). Iheringia, Sér Zool 2009. [DOI: 10.1590/s0073-47212009000400006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new molecular phylogeny for akodontine rodents from Brazil was proposed. The phylogenetic tree was enriched with the area of occurrence and with information on the karyotype of the samples. Based on this enriched tree, and with a described methodology, hypotheses were proposed on the karyotype and area of occurrence of the ancestors of each Clade. Thus it was possible to discuss hypotheses on chromosome evolution of the group, and on dispersion events from the "area of original differentiation" of akodontines in the Andes. Chromosome evolution started with high diploid numbers (2n=52) and showed a tendency to reduction (until 2n=14 in more recent clades). Independent side-branches of the tree showed 2n reduction and in one case the 2n increased. At least four dispersion events from the Andes down to South-eastern Brazil were proposed. The results should suggest the direction of new studies on comparative karyology.
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HAYES KENNETHA, COWIE ROBERTH, THIENGO SILVANAC. A global phylogeny of apple snails: Gondwanan origin, generic relationships, and the influence of outgroup choice (Caenogastropoda: Ampullariidae). Biol J Linn Soc Lond 2009. [DOI: 10.1111/j.1095-8312.2009.01246.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Barros MC, Sampaio I, Schneider H. Novel 12S mtDNA findings in sloths (Pilosa, Folivora) and anteaters (Pilosa, Vermilingua) suggest a true case of long branch attraction. Genet Mol Biol 2008. [DOI: 10.1590/s1415-47572008000400029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Hafner JC, Light JE, Hafner DJ, Hafner MS, Reddington E, Rogers DS, Riddle BR. Basal Clades and Molecular Systematics of Heteromyid Rodents. J Mammal 2007. [DOI: 10.1644/06-mamm-a-413r1.1] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Abstract
Molecular studies have led recently to the proposal of a new super-ordinal arrangement of the 18 extant Eutherian orders. From the four proposed super-orders, Afrotheria and Xenarthra were considered the most basal. Chromosome-painting studies with human probes in these two mammalian groups are thus key in the quest to establish the ancestral Eutherian karyotype. Although a reasonable amount of chromosome-painting data with human probes have already been obtained for Afrotheria, no Xenarthra species has been thoroughly analyzed with this approach. We hybridized human chromosome probes to metaphases of species (Dasypus novemcinctus, Tamandua tetradactyla, and Choloepus hoffmanii) representing three of the four Xenarthra families. Our data allowed us to review the current hypotheses for the ancestral Eutherian karyotype, which range from 2n = 44 to 2n = 48. One of the species studied, the two-toed sloth C. hoffmanii (2n = 50), showed a chromosome complement strikingly similar to the proposed 2n = 48 ancestral Eutherian karyotype, strongly reinforcing it. Living mammals are classified into three major groups: monotremes, marsupials, and placental mammals or Eutherians, composed of 18 orders. Phylogenetic studies point to Afrotheria (a clade of six endemic African orders) or Xenarthra (armadillos, anteaters, and sloths, mostly found in Central and South America) as the most basal Eutherian group. One of the most daring aims of molecular cytogenetics in the past decade has been to establish the karyotype present in a common ancestor of all Eutherians. The approach used, cross-species chromosome painting, involves the use of probes from specific chromosomes or chromosome segments from one species, which are hybridized to metaphases of another species, highlighting regions of homology between both genomes. More than 60 species have already been analyzed with this method, and it is believed that the ancestral karyotype had 44, 46, or 48 chromosomes. The authors, using human chromosomes as probes to study three Xenarthra species, found that one of them, the two-toed sloth Choloepus hoffmannii (2n = 50), has a karyotype strikingly similar to the proposed 2n = 48 ancestral Eutherian complement. This observation, besides reinforcing the hypothesized karyotype, suggests that Xenarthra may be at the root of the Eutherian tree.
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Affiliation(s)
- Marta Svartman
- Comparative Molecular Cytogenetics Core, Genetics Branch, National Cancer Institute-Frederick, Frederick, Maryland, USA.
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de Moraes-Barros N, Silva JAB, Miyaki CY, Morgante JS. Comparative Phylogeography of the Atlantic Forest Endemic Sloth (Bradypus torquatus) and the Widespread Three-toed Sloth (Bradypus variegatus) (Bradypodidae, Xenarthra). Genetica 2006; 126:189-98. [PMID: 16502095 DOI: 10.1007/s10709-005-1448-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The comparative phylogeographic study of the maned sloth (Bradypus torquatus) and the three-toed sloth (Bradypus variegatus) was performed using a segment of mitochondrial DNA (mtDNA) control region. We examined 19 B. torquatus from two regions and 47 B. variegatus from three distant regions of Atlantic forest. This first characterization of molecular diversity indicates a great diversity (B. torquatus: h = 0.901 +/- 0.039 and pi = 0.012 +/- 0.007; B. variegatus: h = 0.699 +/- 0.039 and pi = 0.010 +/- 0.006) and very divergent mitochondrial lineages within each sloth species. The different sampled regions carry distinct and non-overlapping sets of mtDNA haplotypes and are genetically divergent. This phylogeographic pattern may be characteristic of sloth species. In addition, we infer that two main phylogeographic groups exist in the Atlantic forest representing a north and south distinct divergence.
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Affiliation(s)
- Nadia de Moraes-Barros
- Departamento de Genética e Biologia Evolutiva Laboratório de Biologia Evolutiva e Conservação de Vertebrados, Universidade de São Paulo, C.P. 11.461, 05422-970, São Paulo, SP, Brazil.
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Orr CM. Knuckle-walking anteater: a convergence test of adaptation for purported knuckle-walking features of African Hominidae. Am J Phys Anthropol 2005; 128:639-58. [PMID: 15861420 DOI: 10.1002/ajpa.20192] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Appeals to synapomorphic features of the wrist and hand in African apes, early hominins, and modern humans as evidence of knuckle-walking ancestry for the hominin lineage rely on accurate interpretations of those features as adaptations to knuckle-walking locomotion. Because Gorilla, Pan, and Homo share a relatively close common ancestor, the interpretation of such features is confounded somewhat by phylogeny. The study presented here examines the evolution of a similar locomotor regime in New World anteaters (order Xenarthra, family Myrmecophagidae) and uses the terrestrial giant anteater (Myrmecophaga tridactyla) as a convergence test of adaptation for purported knuckle-walking features of the Hominidae. During the stance phase of locomotion, Myrmecophaga transmits loads through flexed digits and a vertical manus, with hyperextension occurring at the metacarpophalangeal joints of the weight-bearing rays. This differs from the locomotion of smaller, arboreal anteaters of outgroup genera Tamandua and Cyclopes that employ extended wrist postures during above-branch quadrupedality. A number of features shared by Myrmecophaga and Pan and Gorilla facilitate load transmission or limit extension, thereby stabilizing the wrist and hand during knuckle-walking, and distinguish these taxa from their respective outgroups. These traits are a distally extended dorsal ridge of the distal radius, proximal expansion of the nonarticular surface of the dorsal capitate, a pronounced articular ridge on the dorsal aspects of the load-bearing metacarpal heads, and metacarpal heads that are wider dorsally than volarly. Only the proximal expansion of the nonarticular area of the dorsal capitate distinguishes knuckle-walkers from digitigrade cercopithecids, but features shared with digitigrade primates might be adaptive to the use of a vertical manus of some sort in the stance phase of terrestrial locomotion. The appearance of capitate nonarticular expansion and the dorsal ridge of the distal radius in the hominin lineage might be indicative of a knuckle-walking ancestry for bipedal hominins if interpreted within the biomechanical and phylogenetic context of hominid locomotor evolution.
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Affiliation(s)
- Caley M Orr
- Department of Anthropology, Institute of Human Origins, and NSF IGERT Program in Neural and Musculoskeletal Adaptation in Form and Function, Arizona State University, Tempe, Arizona 85287-2402, USA.
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