Population size does not influence mitochondrial genetic diversity in animals

Within-species genetic diversity is thought to reflect population size, history, ecology, and ability to adapt. Using a comprehensive collection of polymorphism data sets covering approximately 3000 animal species, we show that the widely used mitochondrial DNA (mtDNA) marker does not reflect species abundance or ecology: mtDNA diversity is not higher in invertebrates than in vertebrates, in marine than in terrestrial species, or in small than in large organisms. Nuclear loci, in contrast, fit these intuitive expectations. The unexpected mitochondrial diversity distribution is explained by recurrent adaptive evolution, challenging the neutral theory of molecular evolution and questioning the relevance of mtDNA in biodiversity and conservation studies.     

Serological and molecular comparison of Mannheimia haemolytica and Pasteurella trehalosi strains isolated from wild and domestic ruminants in the French Alps

Over a period of 17 years, 84 bacterial isolates identified as Mannheimia haemolytica or M. glucosida, and 52 isolates identified as Pasteurella trehalosi were detected in the lungs of domestic and wild ruminants in the French Alps. The isolates were serotyped according to their surface capsular antigens, and those sharing common antigens were further characterized by pulsed field gel electrophoresis. The results showed that the bacterial isolates included in the study clustered according to the host species from which they were isolated. These findings indicate that the transmission of serotypes of M. haemolytica, M. glucosida or P. trehalosi from an animal host in which they are common to another species sharing the same geographical space may be a rare epidemiological event.     

<Emphasis Type="Italic">Fusarium temperatum</Emphasis> isolated from maize in France

The presence of Fusarium temperatum in France was investigated by analyzing 40 Fusarium strains, previously isolated from infected maize ears in 2011 and formerly identified as Fusarium subglutinans based on morphological characteristics. In this study, 26 strains out of the 40 were identified as F. temperatum and 14 as F. subglutinans based on sequencing of the translation elongation factor 1α gene. The phylogenetic analysis showed that the two species represented two clades strongly supported by bootstrap values. The pathogenicity of F. temperatum strains was confirmed on maize ears. This study provides new information about F. temperatum isolated from maize in France.     

An Efficient ELLAM Implementation for Modeling Solute Transport in Fractured Porous Media

The goal of this study is to introduce an adaptation of the Eulerian-Lagrangian localized adjoint method (ELLAM) for the simulation of mass transport in fractured porous media, and to evaluate the performance of ELLAM in such a case. The fractures are represented explicitly using the discrete fracture model. The velocity field was calculated using the mixed hybrid finite element method. A sound ELLAM implementation is developed to address numerical artifacts (spurious oscillations and numerical dispersion) arising from the presence of fractures. The efficiency of the developed ELLAM implementation was further improved by taking advantage of the parallel computing on shared memory architecture for the tasks related to particles tracking and linear system resolving. The performance of ELLAM was tested by comparing its results with the Eulerian discontinuous Galerkin method based on several benchmark problems dealing with different fracture configurations. The results highlight the robustness and accuracy of ELLAM, as it allows the use of large time steps, and overcomes the Courant-Friedrichs-Lewy (CFL) restriction. The outcome also shows that ELLAM is more efficient when fracture density is increased.     

Quantifying the effects of soil and climate on aboveground biomass production of <Emphasis Type="Italic">Salix miyabeana</Emphasis> SX67 in Quebec

Soil and climatic conditions for optimizing aboveground biomass yields of bioenergy short rotation coppices (SRCs) of Salix are not well elucidated. The objective of this study was to identify and quantify the limitations induced by soil and climate, and compare the magnitude of their effects, on annual aboveground yields across ten SRCs of Salix miyabeana SX67 in Quebec, Canada. The effects of weather variation between years on yields were also tested within locations. In five plots per SRC, soil bulk density, particle size, exchangeable cations and bulk composition were analysed, and moisture deficits were estimated using leaf δ¹³C. For each location, numerous weather variables were simulated for spring, summer and the whole growing season. Climate was calculated by averaging weather variables for growing seasons for which annual yields were available. Annual aboveground biomass yields were modelled using linear regression, partitioning of the variance and mixed models with soil, weather and climate variables as predictors. Across SRCs, silt content, soil organic matter, pH, exchangeable Ca and Mg, and total N and Zn were significantly and positively related to aboveground yields (adj. R ² ranging from 0.38 to 0.79). Generally, annual yields were negatively related to summer temperature within SRCs (adj. R ² = 0.92) and drought across SRCs (adj. R ² = 0.54). Partitioning of the variance revealed that soil variables (~80%) had a greater effect on productivity than did climate variables (~10%). In fact, soil properties buffered or exacerbated water shortages and, thus, had a preponderant effect on yield.     

Influence of the surrounding landscape on the colonization rate of cereal aphids and phytovirus transmission in autumn

Ecological control has often focused on factors enhancing control of pests by their natural enemies, while factors reducing the colonization rate of crops by pests have been comparatively neglected. We present an approach to assess landscape influence on the intensity of wheat colonization by a major crop pest, the aphid Rhopalosiphum padi. We used trays containing wheat seedlings to monitor field colonization by R. padi and barley yellow dwarf viruses’ transmission in two areas in France in autumn. We assessed the influence of landscape components likely affecting aphid colonization, i.e. maize and grasslands as source of migrants on the number of aphids landing per tray, as well as the host plant of origin and the viruliferous potential of migrants. During the survey, maize was the main source of migrants. Virus transmission was detected in a few cases (4 % positive assays). Colonization was increased by the presence of maize, but reduced by the presence of grasslands at the landscape scale considered here (i.e. at a radius of 1000 m). Our study contributes to a better understanding of disease dynamics in agricultural landscapes. By identifying features of the landscape that surrounds fields and affects these dynamics, growers can develop more efficient crop protection strategies relying on habitat manipulation and rational use of pesticides.     

Beating heart mitral valve replacement with a bovine pericardial bioprosthesis for treatment of mitral valve dysplasia in a Bull Terrier

OBJECTIVES: To describe an open, beating heart surgical technique and use of a bovine pericardial prosthetic valve for mitral valve replacement (MVR) in the dog. STUDY DESIGN: Clinical case report. ANIMALS: Male Bull Terrier (17-month-old, 26 kg) with mitral valve dysplasia and severe regurgitation. METHODS: A bovine pericardial bioprosthesis was used to replace the mitral valve using an open beating heart surgical technique and cardiopulmonary bypass. RESULTS: Successful MVR was achieved using a beating heart technique. Mitral regurgitation resolved and cardiac performances improved (left ventricular end-diastolic diameter decreased from 57.6 to 48.7 mm, and left atrium/aorta ratio returned to almost normal, from 1.62 to 1.19). Cardiopulmonary by-pass time and total surgical duration were decreased compared with standard cardioplegic techniques. Surgical recovery was uneventful and on echocardiography 6 months later valve function was excellent. CONCLUSION: Considering the technique advantages (no cardiac arrest, ischemic reperfusion injury, and hypothermia, or the need for aortic dissection and cannulation for administration of cardioplegic solution), short-term mortality and morbidity may be reduced compared with standard cardioplegic techniques. CLINICAL RELEVANCE: Based on experience in this dog, beating heart mitral valvular replacement is a seemingly safe and viable option for the dog and bovine pericardial prosthesis may provide better long-term survival than mechanical prostheses.