Roedores sigmodontinos del sitio arqueológico "El Divisadero Monte 6" (Holoceno tardío, Buenos Aires, Argentina): taxonomía y reconstrucción ambiental

Se describe el ensamble de roedores sigmodontinos recuperado en el sitio arqueológico “El Divisadero Monte 6”, emplazado sobre la franja de humedales costeros de la Bahía de Samborombón (partido de General Lavalle, provincia de Buenos Aires, Argentina). Una datación de 540 ± 60 años radiocarbónicos antes del presente ubica la muestra en el Holoceno tardío. El ensamble está dominado por sigmodontinos frecuentes actualmente en el área (e.g., Akodon azarae, Oligoryzomys flavescens, Holochilus brasiliensis) y otros extintosregionalmente (e.g., Bibimys torresi, Pseudoryzomys simplex). La disminución de riqueza y diversidad que reflejan las comunidades actuales de sigmodontinos podría estar vinculada con el impacto antrópico que sufrió la región en los últimos siglos.Sigmodontine rodents from “El Divisadero Monte 6” archaeological site (Late Holocene, Buenos Aires, Argentina): Taxonomy and enviromental reconstruction. We describe the assemblage of sigmodontine rodents from the archaeological site “El Divisadero Monte 6”. This site is placed within the fringe of coastal wetlands of the Bahía de Samborombón (General Lavalle county, Buenos Aires province, Argentina). A radiocarbon date of 540 ± 60 years B.P. indicates a Late Holocene age for the studied sample. The studied sample is mostly composed by species still frequent in the area (e.g., Akodon azarae, Oligoryzomys flavescens, Holochilus brasiliensis) and other sigmodontines regionally extinct (e.g.. Bibimys torresi, Pseudoryzomys simplex). The observed decrease both in richness and diversity in recent samples probably was triggered by human-made disturbances over the pampean region during the last centuries.Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico. Unidad de Investigación Diversidad, Sistemática y Evolución; Argentina;Fil: Pardiñas, Ulyses Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico. Unidad de Investigación Diversidad, Sistemática y Evolución; Argentina;Fil: Aldazabal, Veronica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentina; Universidad de Buenos Aires. Facultad de Arquitectura y Urbanismo. Instituto de Arte Americano e Investigaciones Estéticas “Mario J. Buschiazzo”. Centro de Arqueologia Urbana; Argentina;Fil: Silveira, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas. Unidad de Investigaciones Prehistóricas y Arqueológicas; Argentina;Fil: Eugenio, Emilio Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas. Unidad de Investigaciones Prehistóricas y Arqueológicas; Argentina

The phylogenetic position of the enigmatic Atlantic forest-endemic spiny mouse Abrawayaomys (Rodentia: Sigmodontinae)

Background The phylogenetic position of the sigmodontine genus Abrawayaomys, historically assigned to the tribe Thomasomyini or considered a sigmodontine incertae sedis, was assessed on the basis of nuclear and mitochondrial DNA sequences obtained from four individuals from different localities in the Atlantic forest of Brazil. Sequences of Abrawayaomys were analyzed in the context of broad taxonomic matrices by means of maximum-likelihood (ML) and Bayesian analyses (BA). Results The phylogenetic position of Abrawayaomys differed depending on the gene analyzed and the analysis performed (interphotoreceptor retinoid-binding protein (IRBP) ML: sister to Thomasomyini; IRBP BA: sister to Akodontini; cytochrome (Cyt) b ML: sister to Neotomys; and Cyt b BA: sister to Reithrodontini). With the sole exception of the BA based on Cyt b sequences, where the Abrawayaomys-Reithrodon clade had strong support, all sister-group relationships involving Abrawayaomys lacked any significant support. Conclusions As such, Abrawayaomys constitutes the only representative so far known of one of the main lineages of the sigmodontine radiation, differing from all other Atlantic forest sigmodontine rodents by having a unique combination of morphological character states. Therefore, in formal classifications, it should be regarded as a Sigmodontinae incertae sedis.Fil: Ventura, Karen. Universidade de São Paulo. Instituto de Biociências. Departamento de Genética e Biologia Evolutiva; BrasilFil: Silva, Maria José. Instituto Butantan. Laboratório de Ecologia e Evolução; BrasilFil: Geise, Lena. Universidade do Estado do Rio de Janeiro. Instituto de Biologia. Departamento de Zoologia. Laboratório de Mastozoologia; BrasilFil: Leite, Yuri L. R.. Universidade Federal Do Espirito Santo; BrasilFil: Pardiñas, Ulyses Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Yonenaga Yassuda, Yatiyo. Universidade de São Paulo. Instituto de Biociências. Departamento de Genética e Biologia Evolutiva; BrasilFil: D Elía, Guillermo. Universidad Austral de Chile. Facultad de Ciencias. Instituto de Ciencias Ambientales y Evolutivas; Chil

Holocene stability and recent dramatic changes in micromammalian communities of northwestern Patagonia

Micromammalian fossil sequences of two classical archaeological sites, Cueva Traful I (CTI) and Cueva Epullán Grande (LL), both in the province of Neuquén, northwestern Patagonia, Argentina, were studied. These sequences cover the entire Holocene, with assemblages mainly composed by rodent and marsupial remains accumulated by owls. Both sites are located near the ecotone fringes of the major vegetation units currently present in Patagonia: Forest-Patagonian steppe (CTI) and Patagonian steppe-Monte desert (LL). Comparisons between fossil and recent owl pellet samples in a regional approach indicated that micromammal communities remained stable over the major part of the last 10 ka, with some minor expansion of desert adapted taxa to the west since the middle Holocene, and a dramatic change in the assemblages during the last 100e150 years. Two alternative but not contradictory explanations can be presented to interpret the stable period. First, climate-environmental changes were not of sufficient magnitude to produce a clear reorganization of micromammal communities. Forest did not invade CTI surroundings, and Monte did not reach around LL. Second, the basic structure of northwestern Patagonian steppe micromammal communities was resilient to minor or moderate climate-environmental changes. The strong shift depicted in the studied sequences in very recent times (100e150 years) can be linked to human impact on the regional environment. This change involves a deep restructuration of small mammal communities ranging from virtual extirpations of some species to dramatic increments of opportunistic taxa. A century of sheep overgrazing, coupled with the introduction of exotic shrubs, was the main factor driving the configuration of present small mammal assemblages in northwestern Patagonia.Fil: Pardiñas, Ulyses Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin

Taxonomic status of Mus talpinus Lund (Rodentia: Sigmodontinae) from the Quaternary deposits of Lagoa Santa, Minas Gerais, Brazil and its paleoenvironmental meaning

Mus talpinus, a fossil sigmodontine rodent exhumated by P. W. Lund from Quaternary deposits in the Lagoa Santa area, Brazil, has been varyingly allocated to the genera Oxymycterus, Blarinomys or Juscelinomys. After our examination of the holotype, an anterior fragment of the skull from Lapa da Serra das Abelhas, Minas Gerais, Brazil, we refer the name talpinus to the genus Brucepattersonius. These mice are sylvan akodontines, widespread in the Atlantic Forest, with the nearest extant record approximately 250 km southeast of Lagoa Santa. The addition of Brucepattersonius to the fossil sigmodontine fauna of Lagoa Santa suggests a non-analogous assemblage of species in this area during the Late Pleistocene.Fil: Pardiñas, Ulyses Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin

Congruence between morphology and phylogeography in the Patagonian long-clawed mouse Chelemys macronyx (Rodentia, Cricetidae)

Chelemys macronyx is a medium-sized, long-clawed sigmodontine of fossorial habits, distributed between 33°20′ and 51°30′S in the central and southern Andes of Argentina and Chile. Phylogeographic studies based on the analysis of mitochondrial DNA showed that this rodent has a shallow genealogy geographically structured into two main clades: one in the northern part of its range, at high-Andean localities in the Argentinean provinces of Mendoza and northern Neuquén, and the other covering medium- to low-elevation areas from northwestern Neuquén to southern Chile and Argentina. Qualitative and quantitative morphological characters show the existence of two main morphotypes of C. macronyx. Northern populations are characterized by a mesopterygoid fossa rounded at its anterior border and by a large and nearly circular foramen ovale, whereas in central and southern populations the mesopterygoid fossa is quadrate with an ovate to piriform foramen ovale. The described morphological variation is in congruence with the phylogeographic patterns identified by molecular markers. In light of these results, we suggest a simplified taxonomic arrangement on which two subspecies are recognized within C. macronyx, a northern one and a southern one for which the names C. m. macronyx and C. m. vestitus correspond, respectively.Fil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Pardiñas, Ulyses Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: D'elía, Guillermo. Universidad Austral de Chile. Facultad de Ciencias. Instituto de Ciencias Ambientales y Evolutivas; Chil

A phylogenetic appraisal of Sigmodontinae (Rodentia, Cricetidae) with emphasis on phyllotine genera: systematics and biogeography

Here, we present a comprehensive phylogenetic analysis based on nuclear and mitochondrial DNA sequences of rodents of the subfamily Sigmodontinae. The emphasis is placed on the large tribe Phyllotini; sampling includes for the first time in any molecular-based phylogenetic analysis representatives of several genera traditionally considered to be phyllotines. Given the broad taxonomic sampling, results provide substantial improvements in our knowledge on both the structure of the sigmodontine radiation and of phyllotine phylogenetic relationships. For instance, the tribe Ichthyomyini was not recovered monophyletic. Similarly, in a novel hypothesis on the contents of the tribe Phyllotini, it is shown that unlike Galenomys, the genera Chinchillula, Neotomys and Punomys are not phyllotines. The later genera together with Andinomys, Euneomys, Irenomys and Juliomys form part of novel generic clades of mostly Andean sigmodontine rodents. More in general, results strongly suggest the occurrence of several instances of putative morphological convergence among distinct sigmodontine lineages (e.g. among now considered to be ichthyomyines; between Phyllotini and some Andean taxa; among Euneomys-Neotomys and Reithrodon). Finally, we suggest that the historical biogeography of the sigmodontine rodents is far more complex than earlier envisioned.Fil: Salazar Bravo, Jorge. Texas Tech University. Department of Biological Sciences; Estados UnidosFil: Pardiñas, Ulyses Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: D'elía, Guillermo. Universidad Austral de Chile. Instituto de Ciencias Ambientales y Evolutivas; Estados Unido

Dating an impressive Neotropical radiation: Molecular time estimates for the Sigmodontinae (Rodentia) provide insights into its historical biogeography

With about 400 living species and 82 genera, rodents of the subfamily Sigmodontinae comprise one of the most diverse and more broadly distributed Neotropical mammalian clades. There has been much debate on the origin of the lineage or the lineages of sigmodontines that entered South America, the timing of entrance and different aspects of further diversification within South America. The ages of divergence of the main lineages and the crown age of the subfamily were estimated by using sequences of the interphotoreceptor retinoid binding protein and cytochrome b genes for a dense sigmodontine and muroid sampling. Bayesian inference using three fossil calibration points and a relaxed molecular clock estimated a middle Miocene origin for Sigmodontinae (∼12 Ma), with most tribes diversifying throughout the Late Miocene (6.9–9.4 Ma). These estimates together results of analyses of ancestral area reconstructions suggest a distribution for the most recent common ancestor of Sigmodontinae in Central-South America and a South American distribution for the most recent common ancestor of Oryzomyalia.Fil: Parada, Andrés. Universidad Católica de Chile; ChileFil: Pardiñas, Ulyses Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Salazar Bravo, Jorge. Texas Tech University. Department of Biological Sciences; Estados UnidosFil: D'elía, Guillermo. Universidad Austral de Chile. Facultad de Ciencias. Instituto de Ciencias Ambientales y Evolutivas; ChileFil: Palma, R. Eduardo. Universidad Católica de Chile; Chil

Bats at the end of the world: new distributional data and fossil record from Patagonia, Argentina

We report new recent and fossil records in Patagonia for six and three bat species, respectively. These findings significantly increase the previously known number of localities for these mammals in this entire region, filling gaps between previous references for some species (e.g., Histiotus macrotus) and/or extending by 140–350 km the range of others (e.g., Myotis chiloensis, M. levis, Lasiurus varius). In addition, we report for the second time the vespertilionid bat Lasiurus blossevillii in Patagonia. Fossils are mostly restricted to the Late Holocene epoch, and the recorded assemblages are similar to the recent ones. A preliminary analysis of richness indicates that bat diversity south of the Colorado River (around 39°S) decreases from five to six species in the northwestern to one species in the southeastern, changing abruptly around 43°S–46°S. Compared with similar latitudes of the Northern Hemisphere, bat diversity in the Neotropics follows a similar pattern, with <20 taxa occurring south of 35°S.Fil: Udrizar Sauthier, Daniel Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Teta, Pablo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Formoso, Anahí Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Bernardis, Adela María. Universidad Nacional del Comahue. Facultad de Ciencias del Ambiente y la Salud. Departamento de Ciencias del Ambiente; ArgentinaFil: Wallace, Patricio.Fil: Pardiñas, Ulyses Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin

New radiometric ⁴⁰Ar–³⁹Ar dates and faunistic analyses refine evolutionary dynamics of Neogene vertebrate assemblages in southern South America

The vertebrate fossil record of the Pampean Region of Argentina occupies an important place in South American vertebrate paleontology. An abundance of localities has long been the main basis for constructing the chronostratigraphical/geochronological scale for the late Neogene-Quaternary of South America, as well as for understanding major patterns of vertebrate evolution, including the Great American Biotic Interchange. However, few independently-derived dates are available for constraining this record. In this contribution, we present new ⁴⁰Ar/³⁹ dates on escorias (likely the product of meteoric impacts) from the Argentinean Atlantic coast and statistically-based biochronological analyses that help to calibrate Late Miocene-Pliocene Pampean faunal successions. For the type areas of the Montehermosan and Chapadmalalan Ages/Stages, our results delimit their age ranges to 4.7-3.7 Ma and ca. 3.74-3.04 Ma, respectively. Additionally, from Buenos Aires Province, dates of 5.17 Ma and 4.33 Ma were recovered for "Huayquerian" and Montehermosan faunas. This information helps to better calibrate important first appearances of allochthonous taxa in South America, including one of the oldest records for procyonids (7.24-5.95 Ma), cricetids (6.95-5.46 Ma), and tayassuids (> 3.74 Ma, oldest high-confidence record). These results also constrain to ca. 3 Ma the last appearances of the autochthonous sparassodonts, as well as terror birds of large/middle body size in South America. South American faunal turnover during the late Neogene, including Late Pliocene extinctions, is interpreted as a consequence of knock-on effects from global climatic changes and initiation of the icehouse climate regime.Facultad de Ciencias Naturales y Muse