Extensive introgression at late stages of species formation: Insights from grasshopper hybrid zones

The process of species formation is characterized by the accumulation of multiple reproductive barriers. The evolution of hybrid male sterility, or Haldane's rule, typically characterizes later stages of species formation, when reproductive isolation is strongest. Yet, understanding how quickly reproductive barriers evolve and their consequences for maintaining genetic boundaries between emerging species remains a challenging task because it requires studying taxa that hybridize in nature. Here, we address these questions using the meadow grasshopper Pseudochorthippus parallelus, where populations that show multiple reproductive barriers, including hybrid male sterility, hybridize in two natural hybrid zones. Using mitochondrial data, we infer that such populations diverged some 100,000 years ago, at the beginning of the last glacial cycle in Europe. Nuclear data show that contractions at multiple glacial refugia, and post-glacial expansions have facilitated genetic differentiation between lineages that today interact in hybrid zones. We find extensive introgression throughout the sampled species range, irrespective of the current strength of reproductive isolation. Populations exhibiting hybrid male sterility in two hybrid zones show repeatable patterns of genomic differentiation, consistent with shared genomic constraints affecting ancestral divergence or with the role of those regions in reproductive isolation. Together, our results suggest that reproductive barriers that characterize late stages of species formation can evolve relatively quickly, particularly when associated with strong demographic changes. Moreover, we show that such barriers persist in the face of extensive gene flow, allowing future studies to identify associated genomic regions

Towards Global Characterization of Environmental and Climatic Determinants for Seasonal Influenza

No abstract availabl

Electrical and thermal conductivities of reduced graphene oxide/polystyrene composites

The author reports an experimental study of electrical and thermal transport in reduced graphene oxide (RGO)/polystyrene (PS) composites. The electrical conductivity (sigma) of RGO/PS composites with different RGO concentrations at room temperature shows a percolation behavior with the percolation threshold of similar to 0.25 vol. %. Their temperature-dependent electrical conductivity follows Efros-Shklovskii variable range hopping conduction in the temperature range of 30-300K. The thermal conductivity (kappa) of composites is enhanced by similar to 90% as the concentration is increased from 0 to 10 vol. %. The thermal conductivity of composites approximately linearly increases with increasing temperature from 150 to 300 K. Composites with a higher concentration show a stronger temperature dependence in the thermal conductivity. (C) 2014 AIP Publishing LLC

Dimensional Transmutation and Dimensional Regularization in Quantum Mechanics. II: Rotational Invariance

A thorough analysis is presented of the class of central fields of force that exhibit: (i) dimensional transmutation and (ii) rotational invariance. Using dimensional regularization, the two-dimensional delta-function potential and the $D$-dimensional inverse square potential are studied. In particular, the following features are analyzed: the existence of a critical coupling, the boundary condition at the origin, the relationship between the bound-state and scattering sectors, and the similarities displayed by both potentials. It is found that, for rotationally symmetric scale-invariant potentials, there is a strong-coupling regime, for which quantum-mechanical breaking of symmetry takes place, with the appearance of a unique bound state as well as of a logarithmic energy dependence of the scattering with respect to the energy.Comment: 29 pages. To appear in Annals of Physic

Capim-elefante anão sob pastejo II. Valor nutritivo

Dwarf elephantgrass (Pennisetum purpureum Schum.) was evaluated in a grazing trial. Grazing pressure (GP) and grazing cyle (GC) were applied at five levels: GP-500, 1,000, 1,500, 2,000 and 2,500 kg of residual leaf dry matter ha-1 after grazing and CG - 0 (continuous grazing), 14, 28, 42 and 56 days. The GC included a 2-day grazing period plus a specific rest period. A nonrotatable central composite design with 13 treatment combinations in two replications was used. A complete second - order polynomial model was used to analyse the data. The crude protein of leaves and stems increased as GP was increased and GC was shortened. The in vitro, digestibility of leaves, stems and "grazed forage" seemed to be affected quadraticaly by GC. Heavier GPs tended to favour the digestibility of stems. The crude protein of "grazed forage" was increased by shorter GCs. The optimum point for digestibility of "grazed forage" was around GP of 1,500 kg of residual leaf DM ha-1 and 14 days of GC. Leaves had higher nutritive value than stems and the high quality of "grazed forage" revealed the potential of this grass under grazing.O valor nutritivo do capim-elefante anão (Pennisetum purpureum Schum.) foi estudado num ensaio de pastejo. Pressão de pastejo (PP) e ciclo de pastejo (CP) foram aplicados em cinco níveis cada: PP-500, 1.000, 1.500, 2.000 e 2.500 kg de MS de folha residual ha-1 após o pastejo e CP-0 (pastejo contínuo), 14, 28, 42 e 56 dias. Cada CP incluiu dois dias de pastejo e um período de descanso específico para cada nível. O desenho experimental foi um composto central, não-rotável, com treze combinações em duas repetições. O modelo usado foi o polinômio completo do segundo grau. A proteína bruta das folhas e dos colmos aumentou com a elevação da PP e diminuição do CP. A digestibilidade in vitro das folhas, colmos e "forragem consumida" pareceu responder quadraticamente ao CP. As PPs mais altas tenderam a favorecer a digestibilidade dos colmos. A proteína da "forragem consumida" foi estimulada por CPs curtos. O ponto ótimo para digestibilidade da "forragem consumida" ficou em torno da combinação de 1.500 kg de MS de folha residual ha-1 de PP com 14 dias de CP. O valor nutritivo das folhas foi bem maior que o dos colmos, e a excelente qualidade da "forragem consumida" revelou o grande potencial desse capim sob pastejo

When enough should be enough: Improving the use of current agricultural lands could meet production demands and spare natural habitats in Brazil

Providing food and other products to a growing human population while safeguarding natural ecosystems and the provision of their services is a significant scientific, social and political challenge. With food demand likely to double over the next four decades, anthropization is already driving climate change and is the principal force behind species extinction, among other environmental impacts. The sustainable intensification of production on current agricultural lands has been suggested as a key solution to the competition for land between agriculture and natural ecosystems. However, few investigations have shown the extent to which these lands can meet projected demands while considering biophysical constraints. Here we investigate the improved use of existing agricultural lands and present insights into avoiding future competition for land. We focus on Brazil, a country projected to experience the largest increase in agricultural production over the next four decades and the richest nation in terrestrial carbon and biodiversity. Using various models and climatic datasets, we produced the first estimate of the carrying capacity of Brazil's 115 million hectares of cultivated pasturelands. We then investigated if the improved use of cultivated pasturelands would free enough land for the expansion of meat, crops, wood and biofuel, respecting biophysical constraints (i.e., terrain, climate) and including climate change impacts. We found that the current productivity of Brazilian cultivated pasturelands is 32–34% of its potential and that increasing productivity to 49–52% of the potential would suffice to meet demands for meat, crops, wood products and biofuels until at least 2040, without further conversion of natural ecosystems. As a result up to 14.3 Gt CO2 Eq could be mitigated. The fact that the country poised to undergo the largest expansion of agricultural production over the coming decades can do so without further conversion of natural habitats provokes the question whether the same can be true in other regional contexts and, ultimately, at the global scale

Prevalence of sexual dimorphism in mammalian phenotypic traits.

The role of sex in biomedical studies has often been overlooked, despite evidence of sexually dimorphic effects in some biological studies. Here, we used high-throughput phenotype data from 14,250 wildtype and 40,192 mutant mice (representing 2,186 knockout lines), analysed for up to 234 traits, and found a large proportion of mammalian traits both in wildtype and mutants are influenced by sex. This result has implications for interpreting disease phenotypes in animal models and humans

Homofobia e educação: quando a omissão também é signo de violência

Provocado pelo conceito de "amolador de facas", criado pelo psicólogo Luis Antonio Baptista, este artigo busca discutir alguns aspectos da violência contra estudantes LGBTT e a omissão do tema da diversidade sexual e de gênero no currículo escolar como forma oculta de homofobia e da cumplicidade de educadores e educadoras com essa violência

Measuring the dynamic photosynthome

Background: Photosynthesis underpins plant productivity and yet is notoriously sensitive to small changes inenvironmental conditions, meaning that quantitation in nature across different time scales is not straightforward. The ‘dynamic’ changes in photosynthesis (i.e. the kinetics of the various reactions of photosynthesis in response to environmental shifts) are now known to be important in driving crop yield. Scope: It is known that photosynthesis does not respond in a timely manner, and even a small temporal “mismatch” between a change in the environment and the appropriate response of photosynthesis toward optimality can result in a fall in productivity. Yet the most commonly measured parameters are still made at steady state or a temporary steady state (including those for crop breeding purposes), meaning that new photosynthetic traits remain undiscovered. Conclusions: There is a great need to understand photosynthesis dynamics from a mechanistic and biological viewpoint especially when applied to the field of ‘phenomics’ which typically uses large genetically diverse populations of plants. Despite huge advances in measurement technology in recent years, it is still unclear whether we possess the capability of capturing and describing the physiologically relevant dynamic features of field photosynthesis in sufficient detail. Such traits are highly complex, hence we dub this the ‘photosynthome’. This review sets out the state of play and describes some approaches that could be made to address this challenge with reference to the relevant biological processes involved