Diversidad genética de Pinus pinaster en la Península Ibérica: correlación entre isoenzimas y caracteres cuantitativos

The estimation of genetic diversity using molecular markers is a major component of genetic conservation programs. However, molecular data are only weakly correlated with adaptive variation, which seriously limits the value of molecular information for guiding conservation policies. In this paper, we used allozyme markers to analyse the distribution of gene diversity in the native range of Pinus pinaster Ait. in the Iberian Peninsula, including seven marginal populations close to the Mediterranean Basin. Then, the variability of three quantitative traits (total height, stem form and survival) was computed using data from a multisite provenance test in central Spain and the two data sets were compared. Within the general pattern of variation, marginal populations presented levels of diversity closely related to those of nearby central populations, clearly suggesting that historical factors were more important than actual population sizes in determining levels of observed diversity. A weak but nevertheless significant correlation between allozymes and quantitative variability was found in maritime pine. Environmental gradients, as measured by geographic variables, are suggested to have selective effects on quantitative traits and to influence effective population size, which might explain the weak correlation found between allozyme and adaptive variability.Uno de los principales componentes de los programas de conservación genética es el uso de marcadores moleculares para la estimación de la diversidad genética. A pesar de ello, la variación observada en marcadores moleculares está débilmente correlacionada con la variación adaptativa, lo que limita seriamente la aplicación de estos estudios en el desarrollo de políticas de conservación. En este trabajo, se compara la distribución de la diversidad genética de Pinus pinaster Ait. en la Península Ibérica obtenida con marcadores moleculares (isoenzimas) y caracteres cuantitativos (altura, forma del fuste y supervivencia). El estudio incluye siete poblaciones marginales. Éstas, muestran valores de diversidad similares a los de poblaciones centrales próximas lo que sugiere una gran importancia de los procesos históricos regionales frente a efectos relacionados con el tamaño efectivo poblacional. La correlación de los marcadores moleculares utilizados con los caracteres cuantitativos medidos en los ensayos de campo es débil, aunque significativa. Esta correlación podría explicarse considerando efectos selectivos en respuesta a gradientes ambientales que afectan a su vez el tamaño efectivo de las poblaciones

O impacto do homem na estrutura de uma espécie: Portugal, um paradigma

A bacia do Mediterrâneo é caracterizada pelo tradicional desaparecimento da floresta devido à acção do Homem e o impacto humano tem tido influência na alteração da diversidade genética. O pinheiro bravo ocorre em populações fragmentadas na região oeste da bacia do Mediterrâneo e a sua área de distribuição tem sido alterada nos últimos séculos devido a intensa florestação, em particular no SW de França e no Noroeste da Península Ibérica e, também, devido ao comportamento invasivo desta espécie em áreas perturbadas do ponto de vista ecológico. Nesta apresentação pretendemos sintetizar e discutir o resultado de estudos que utilizaram técnicas moleculares para revelar a diversidade do pinheiro bravo e, também, o impacto humano na sua estrutura genética; que é demonstrado paradigmaticamente em Portugal. Os parâmetros genéticos estimados com base em microsatélites do cloroplasto (cpSSR) revelaram que a diversidade genética é muito elevada ao nível da distribuição da espécie. Observou-se uma clara e significativa diferenciação entre grupos de populações de diferente origem geográfica (Portugal, França, Itália, Espanha e Marrocos). Pelo contrário, o grau de divergência dentro dos países é geralmente muito baixo ou próximo de zero, o que indica uma variação homogénea dentro dos grupos. A presença de diferenciação entre grupos de populações de diferentes áreas reflecte a existência de diferentes refúgios durante o Quaternário. Em França, o padrão haplotípico sugere uma mistura de material proveniente de diferentes origens. Só foram encontrados 3 mitótipos, usando marcadores mitocondriais, marcador de herança maternal, o que proporciona uma imagem clara de áreas colonizadas a partir dos diferentes refúgios; nem uma só população possui uma composição mista. Uma análise filogenética feita com base em isoenzimas mostrou que a estrutura geográfica do pinheiro bravo na Península Ibérica (PI) é muito elevada. As populações de Noroeste formam um grupo e as de Sudeste outro. Observou-se níveis elevados de diversidade nas populações de Este e Sul e uma redução importante da variabilidade em populações da região Noroeste da PI. No entanto, pode ter existido em Portugal um refúgio, pois o pinheiro bravo pode ter sobrevivido durante a última glaciação em zonas abrigadas e de baixa altitude junto ao Oceano Atlântico, o que parece também ser evidente devido a descobertas de pólen e carvão fóssil. A distribuição da variação genética do pinheiro bravo em Portugal, observada através de cpSSR indica que a diferenciação entre populações é baixa e que a diversidade existe principalmente dentro das populações. Não se observa nenhum padrão geográfico, mas as evidências existentes de uma forte influência antrópica antropogénica associada a um fluxo genético extensivo poderiam explicar esse resultado

Hodge polynomials of some moduli spaces of Coherent Systems

When $k<n$, we study the coherent systems that come from a BGN extension in which the quotient bundle is strictly semistable. In this case we describe a stratification of the moduli space of coherent systems. We also describe the strata as complements of determinantal varieties and we prove that these are irreducible and smooth. These descriptions allow us to compute the Hodge polynomials of this moduli space in some cases. In particular, we give explicit computations for the cases in which $(n,d,k)=(3,d,1)$ and $d$ is even, obtaining from them the usual Poincar\'e polynomials.Comment: Formerly entitled: "A stratification of some moduli spaces of coherent systems on algebraic curves and their Hodge--Poincar\'e polynomials". The paper has been substantially shorten. Theorem 8.20 has been revised and corrected. Final version accepted for publication in International Journal of Mathematics. arXiv admin note: text overlap with arXiv:math/0407523 by other author

From angle-action to Cartesian coordinates: A key transformation for molecular dynamics

The transformation from angle-action variables to Cartesian coordinates is a crucial step of the (semi) classical description of bimolecular collisions and photo-fragmentations. The basic reason is that dynamical conditions corresponding to experiments are ideally generated in angle-action variables whereas the classical equations of motion are ideally solved in Cartesian coordinates by standard numerical approaches. To our knowledge, the previous transformation is available in the literature only for triatomic systems. The goal of the present work is to derive it for polyatomic ones.Comment: 10 pages, 11 figures, submitted to J. Chem. Phy

From circular paths to elliptic orbits: A geometric approach to Kepler's motion

The hodograph, i.e. the path traced by a body in velocity space, was introduced by Hamilton in 1846 as an alternative for studying certain dynamical problems. The hodograph of the Kepler problem was then investigated and shown to be a circle, it was next used to investigate some other properties of the motion. We here propose a new method for tracing the hodograph and the corresponding configuration space orbit in Kepler's problem starting from the initial conditions given and trying to use no more than the methods of synthetic geometry in a sort of Newtonian approach. All of our geometric constructions require straight edge and compass only.Comment: 9 pages, 4 figure

Regeneración natural, establecimiento y primer desarrollo del pino silvestre (Pinus sylvestris L.)

Scots pine (Pinus sylvestris L.) regeneration is a long and complex process in which genetic, physiological, ecological and silvicultural factors are very important. In this paper, a deep study of the processes chain that starts with the initiation of flowers and ends with seedlings settlement is made. The discussion about intraspecific and interspecific competence, initial density and grazing is specially interesting for forest management. The main fields of research are gene dispersion studies, development of production oriented management diagrams and simulation models of regeneration processes. Theoretical work must be complemented with financial analysis of young stands cleaning regimes.La regeneración del pino silvestre (Pinus sylvestris L.) es un proceso largo y complejo en el que adquieren gran importancia los aspectos genéticos, fisiológicos, ecológicos y selvícolas. En este artículo se desarrolla un detallado estudio de los factores que influyen en el establecimiento del regenerado, desde el inicio de los primordios florales hasta los primeros crecimientos del joven fustal. La discusión de los efectos de la competencia, tanto inter como intraespecífica, de la densidad de partida y el pastoreo sobre la producción del rodal presenta especial interés para el gestor forestal. El estudio de la dispersión genética de los árboles padre, el desarrollo de normas selvícolas y la modelización de las fases tempranas del pino silvestre son líneas de investigación prometedoras que deben ser completadas con el análisis financiero de las intervenciones selvícolas en rodales jóvenes

Cattle and Sheep Mixed Grazing 1: Species Equivalence

The effects of mixed grazing of cattle and sheep depend on stocking rate (SR) and species ratio (Nicol, 1997). Calculations of SR and species ratio require the use of species equivalence. Equivalents are often estimated in terms of intake requirements calculated on the basis of LW0.75. Freer (1981) stated that LW0.9 would be more appropriate for comparisons of intake requirements for maintenance of sheep and cattle. Nonetheless, Nolan & Connolly (1977) stated that the equivalence is system-specific and depends on the species being considered. The objective of this experiment was to estimate species equivalence for the evaluation of the introduction of sheep into a cattle dairy system based on grazing in temperate Mexico

Genetic differentiation for size at first reproduction through male versus female functions in the widespread Mediterranean tree Pinus pinaster

Background and Aims The study of local adaptation in plant reproductive traits has received substantial attention in short-lived species, but studies conducted on forest trees are scarce. This lack of research on long-lived species represents an important gap in our knowledge, because inferences about selection on the reproduction and life history of short-lived species cannot necessarily be extrapolated to trees. This study considers whether the size for first reproduction is locally adapted across a broad geographical range of the Mediterranean conifer species Pinus pinaster. In particular, the study investigates whether this monoecious species varies genetically among populations in terms of whether individuals start to reproduce through their male function, their female function or both sexual functions simultaneously. Whether differences among populations could be attributed to local adaptation across a climatic gradient is then considered. Methods Male and female reproduction and growth were measured during early stages of sexual maturity of a P. pinaster common garden comprising 23 populations sampled across the species range. Generalized linear mixed models were used to assess genetic variability of early reproductive life-history traits. Environmental correlations with reproductive life-history traits were tested after controlling for neutral genetic structure provided by 12 nuclear simple sequence repeat markers. Key Results Trees tended to reproduce first through their male function, at a size (height) that varied little among source populations. The transition to female reproduction was slower, showed higher levels of variability and was negatively correlated with vegetative growth traits. Several female reproductive traits were correlated with a gradient of growth conditions, even after accounting for neutral genetic structure, with populations from more unfavourable sites tending to commence female reproduction at a lower individual size. Conclusions The study represents the first report of genetic variability among populations for differences in the threshold size for first reproduction between male and female sexual functions in a tree species. The relatively uniform size at which individuals begin reproducing through their male function probably represents the fact that pollen dispersal is also relatively invariant among sites. However, the genetic variability in the timing of female reproduction probably reflects environment-dependent costs of cone production. The results also suggest that early sex allocation in this species might evolve under constraints that do not apply to other conifer

Multiscale Modeling of Composites: Toward Virtual Testing ... and Beyond

Recent developments in the area of multiscale modeling of fiber-reinforced polymers are presented. The overall strategy takes advantage of the separa-tion of length scales between different entities (ply, laminate, and component) found in composite structures. This allows us to carry out multiscale modeling by computing the properties of one entity (e.g., individual plies) at the relevant length scale, homogenizing the results into a constitutive model, and passing this information to the next length scale to determine the mechanical behavior of the larger entity (e.g., laminate). As a result, high-fidelity numerical sim-ulations of the mechanical behavior of composite coupons and small compo-nents are nowadays feasible starting from the matrix, fiber, and interface properties and spatial distribution. Finally, the roadmap is outlined for extending the current strategy to include functional properties and processing into the simulation scheme

¿Qué evalúan los profesores de Educación Secundaria Obligatoria, sobre nutrición vegetal?

En este trabajo se analizan los contenidos que el profesorado considera importantes sobre nutrición vegetal en enseñanza secundaria obligatoria. Para ello se utilizaron las cuestiones de evaluación de una muestra de profesores que en la actualidad imparten el área de ciencias de la naturaleza en ese nivel educativo. El análisis de los resultados nos indica, que el profesorado realiza una selección de contenidos centrada básicamente en aspectos concretos y descriptivos, agrupados sobre todo en el nivel celular y en el proceso de la fotosíntesis, lo que constituye una llamada de atención para la enseñanza de este tema