Distribuição geográfica da diversidade genética e aspectos morfológicos diagnósticosde Marmosa (Micoureus) (Mammalia, Didelphimorphia) na Mata Atlântica

As cuícas do subgênero Marmosa (Micoureus) são marsupiais didelfídeos neotropicais de ampla distribuição na América do Sul, principalmente no Brasil. Esse subgênero sofreu grandes mudanças taxonômicas na última década, sendo que sua espécie com maior distribuição geográfica, Marmosa (Micoureus) demerarae, foi dividida em duas espécies:M. (M.) demerarae (ocorrendo do oeste amazonense até o sul da Bahia) e M. (M.) paraguayana (ocorrendo do norte do Espírito Santo até o Paraguai). O subgênero Micoureus é um dos táxons que exibe uma clara distinção na região do encontro dessas duas espécies, estabelecendo contato nesta região (entre o norte do Espírito Santo e norte de Minas Gerais e sul da Bahia)região esta onde ocorre um processo de intergradação nos espécimes, ou seja, espécimes com assinatura molecular de M. (M.) demerarae possuindo caracteres morfológicos de M. (M.) paraguayana e vice-versa. Assim, o presente estudo visou investigar a diversidade genética e morfológica de Marmosa (Micoureus) tanto na área de contato entre os táxons, quanto em toda extensão da Mata Atlântica, além de tentar esclarecer a confusa taxonomia do grupo. Foram feitas análises genéticas com dois marcadores moleculares irbp (nuclear) e cit b (mitocondrial) em conjunto com o mapeamento de caracteres morfológicos para tentar elucidar a questão da intergradação das espécies na região de contato. O gene mitocondrial recuperou dois clados monofiléticos atribuídos às duas espécies existentes no bioma. Outros clados com estruturação biogeográfica também foram recuperados. Foi descoberto a presença de um possível pseudogene no espécime LPC 75 que poderia levar à uma má interpretação dos dados, que poderia ser o primeiro registro de simpatria para as duas espécies. O marcador nuclear obteve topologias diferentes, não se mostrando eficiente em recuperar as duas linhagens monofiléticas das espécies e nenhum dos clados mostram alguma relação filogeográfica. A análise concatenada recuperou as duas linhagens da Mata Atlântica, mostrando que o cit b desse subgênero é altamente informativo, quando comparado com o gene nuclear utilizado neste trabalho. Analisando a morfologia, descobrimos quatro novos polimorfismos para o caractere diagnóstico número de pêlos nas escamas da cauda ainda não descritos na literatura. Plotando os caracteres morfológicos nas filogenias, concluímos que os mesmo caracteres diagnósticos não são confiáveis para a distinção das espécies. A grande variação morfológica e a grande divergência gênica do DNA mitocondrial poderia nos levar a crer que M. (M.) demerarae e M. (M.) paraguayana tratam-se de uma única espécie.No entanto, a alta divergência genética entre espécimes parapátricos condiz com a distinção entre duas espécies

Topological Vertex, String Amplitudes and Spectral Functions of Hyperbolic Geometry

We discuss the homological aspects of the connection between quantum string generating function and the formal power series associated to the dimensions of chains and homologies of suitable Lie algebras. Our analysis can be considered as a new straightforward application of the machinery of modular forms and spectral functions (with values in the congruence subgroup of $SL(2,{\mathbb Z})$) to the partition functions of Lagrangian branes, refined vertex and open string partition functions, represented by means of formal power series that encode Lie algebra properties. The common feature in our examples lies in the modular properties of the characters of certain representations of the pertinent affine Lie algebras and in the role of Selberg-type spectral functions of an hyperbolic three-geometry associated with $q$-series in the computation of the string amplitudes.Comment: Revised version. References added, results remain unchanged. arXiv admin note: text overlap with arXiv:hep-th/0701156, arXiv:1105.4571, arXiv:1206.0664 by other author

The impact of climate change on the structure of Pleistocene mammoth steppe food webs

Species interactions shape predator-prey networks, impacting community structure and, potentially, ecological dynamics. It is likely that global climatic perturbations that occur over long periods of time have a significant impact on species interactions patterns. However, observations of how these patterns change over time are typically limited to extant communities, which is particularly problematic for communities with long-lived species. Here we integrate stable isotope analysis and network theory to reconstruct patterns of trophic interactions for six independent mammalian communities that inhabited mammoth steppe environments spanning western Europe to eastern Alaska during the Pleistocene. We use a Bayesian mixing model to quantify the proportional contribution of prey to the diets of local predators, and assess how the structure of trophic interactions changed across space and the Last Glacial Maximum (LGM), a global climatic event that severely impacted mammoth steppe communities. We find that large felids had diets that were more constrained than other co-occurring predators, and largely influenced by an increase in {\it Rangifer} abundance after the LGM. Moreover, the structural organization of Beringian and European communities strongly differed: compared to Europe, species interactions in Beringian communities before the LGM were highly compartmentalized, or modular. This modularity was lost during the LGM, and partially recovered after the glacial retreat, and we suggest that changes in modularity among predators and prey may have been driven by geographic insularity

Dynamic RKKY interaction in graphene

The growing interest in carbon-based spintronics has stimulated a number of recent theoretical studies on the RKKY interaction in graphene, based on which the energetically favourable alignment between magnetic moments embedded in this material can be calculated. The general consensus is that the strength of the RKKY interaction in graphene decays as 1/D3 or faster, where D is the separation between magnetic moments. Such an unusually fast decay for a 2-dimensional system suggests that the RKKY interaction may be too short ranged to be experimentally observed in graphene. Here we show in a mathematically transparent form that a far more long ranged interaction arises when the magnetic moments are taken out of their equilibrium positions and set in motion. We not only show that this dynamic version of the RKKY interaction in graphene decays far more slowly but also propose how it can be observed with currently available experimental methods.Comment: 7 pages, 2 figures, submitte

Vanishing DC holographic conductivity from a magnetic monopole condensate

We show how to obtain a vanishing DC conductivity in 3-dimensional strongly coupled QFT's using a massive 2-form field in the bulk that satisfies a special kind of boundary condition. The real and imaginary parts of the AC conductivity are evaluated in this holographic setup and we show that the DC conductivity identically vanishes even for an arbitrarily small (though nonzero) value of the 2-form mass in the bulk. We identify the bulk action of the massive 2-form with an effective theory describing a phase in which magnetic monopoles have condensed in the bulk. Our results indicate that a condensate of magnetic monopoles in a 4-dimensional bulk leads to a vanishing DC holographic conductivity in 3-dimensional strongly coupled QFT's.Comment: 24 pages, 2 figures, accepted for publication in JHE