Variation in the magnitude of a predator's effect from small to large islands

Should the effect of predation be stronger on small islands or on very large islands and mainlands? To make this question precise, we ask here whether the presence/absence of a particular type of predator has greater effects on given types of organisms lower down in the food web, the larger or the smaller the island. To obtain an answer, we used four studies from the same general system, subtropical islands of the Bahamas; here diurnal lizards are the predator, the direct effects are on web spiders (total density, species richness, composite diversity, dominance) and the indirect effects are on herbivory (percent leaf damage) and in part on aerial arthropods (numbers in sticky traps). In two studies, lizards were removed experimentally from enclosures on a very large island; the experiment was performed twice. In a third study, entirely unmanipulated medium-tolarge islands with and without lizards were compared. In a fourth study, lizards were introduced to a set of small-to-medium islands, while two other sets, one naturally with lizards and the other naturally without lizards, served both as controls and as another comparison. Effect magnitude is measured as the ratio of the larger to smaller of the treatment means. An overwhelming tendency exists for lizards to affect spider density, species richness and composite diversity more, the smaller the island; dominance shows little difference. Herbivory is also affected on average more on small islands, but the variation in effect magnitude with island area is less. Aerial arthropods are also affected more on average on small islands, but unlike the other variables the direction of the effect can be negative or positive, and the effect is often very weak. Thus the mainly direct effects of lizards vary more in magnitude than do the mainly indirect effects of lizards. We propose two explanations for effect magnitude to be greater, the smaller the island. First, greater isolation allows less reimmigration of prey on islands, leading to a greater effect magnitude. Second, fewer kinds of predators occur, the smaller the island, implying a greater effect of removing anyone kind.L'efecte de la depredació, hauria d'esser més gran a les illes petites o a les illes molt grans i als continents? Per precisar aquesta questió, al present treball ens demanam si la presència/absència d'un tipus particular de depredador te efectes més grans sobre determinats tipus d'organismes situats més abaix a la xarxa tròfica com mes gran 0 com més petita és l'illa. Per obtenir-ne una resposta, empram quatre estudis dins el mateix sistema general, les illes subtropicals de les Bahamas; les sargantanes diurnes hi són els depredadors, els efectes directes fan damunt les aranyes de tela (densitat total, riquesa d'espècies, diversitat composta, dorninància) i els efectes indirectes són sobre l'herbivoria (percentatge de fulles afectades) i en part sobre els artropodes aeris (nombres a les trampes d'aferrament). A dos estudis, les sargantanes foren substretes experimentalment de tancats a una illa molt gran; l'experiment es va fer dues vegades. A un tercer estudi, varen esser comparades illes mitjanes a grans, sense cap manipulació, amb i sense sargantanes. A un quart estudi, varen esser introduïdes sargantanes a un conjunt d'illes petites a mitjanes, mentre que altres dos conjunts d'illots, un naturalment amb sargantanes i l'altre naturalment sense sargantanes, varen servir com a controls i com a una altra comparació. La magnitud de l'efecte es va mesurar com a la relació entre la major i la menor de les mitjanes del tractament. Es dona una tendència aclaparadora en el sentit que com més petita és l'illa més afecten les sargantanes la densitat d'aranyes, la riquesa d'espècies i la diversitat composta; la dominància d'especies mostra poca diferència. L'herbivoria també està afectada més de mitjana a les illes més petites, però la variació en la magnitud de l'efecte amb l'àrea insular és poca. Eis artropodes aeris també estan afectats més en promig a les illes petites, però, a diferència de les altres variables, la direcció de l'efecte pot esser positiva o negativa, i l'efecte és sovint molt feble. Per això, els efectes principalment directes de les sargantanes varien més en magnitud que els efectes principalment indirectes de les sargantanes. Proposam dues explicacions per al fet que com més petita és l'illa més gran és la magnitud de l'efecte. Primera, un aïllament més gran permet menys reimmigració de les preses, conduïnt a una major magnitud de l'efecte. Segona, a com més petita és l'illa, menys tipus de depredadors hi ha, cosa que implica un efecte més gran quan se'n substreu un qualsevol

Biodegradable Silicon-Containing Elastomers for Tissue Engineering Scaffolds and Shape Memory Polymers

Commonly used thermoplastic biodegradable polymers are generally brittle and lack appreciable elasticity at physiological temperature and thereby fail to mimic the elastic nature of many human soft tissues such as blood vessels. Thus, there is a need for biomaterials which exhibit elasticity. Biodegradable elastomers are promising candidates whose elasticity more closely parallels that of soft tissues. In this research, we developed hybrid biodegradable elastomers comprised of organic and inorganic polymer components in a block copolymer system: poly(e-caprolactone) (PCL) and poly(dimethylsiloxane) (PDMS), respectively. A block structure maintains the distinct properties of the PCL and PDMS components. These elastomers may be useful for the tissue engineering of soft tissues as well as for shape memory polymer (SMP) devices. Tri-block macromers of the form PCLn-block-PDMSm-block-PCLn were developed to permit systematic variations to key features including: PDMS block length, PCL block length, PDMS:PCL ratio, and crosslink density. The macromer was capped with acrylating groups (AcO) to permit their photochemical cure to form elastomers. Thus, a series of biodegradable elastomers were prepared by photocrosslinking a series of macromers in which the PCL blocks varied (n = 5, 10, 20, 30, and 40) and the PDMS block was maintained (m = 37). All elastomers displayed hydrophobic surface properties and high thermal stability. These elastomers demonstrated systematic tuning of mechanical properties as a function of PCL block length or crosslink density. Notable was strains at break as high as 814% making them suitable for elastomeric bioapplications. Elastomers with a critical PCL block length (n = 30 or 40) exhibited shape memory properties. Shape memory polymers based on an organic-inorganic, photocurable silicon-containing polymer system is a first of its kind. This SMP demonstrated strain fixity of 100% and strain recovery near 100% after the third thermomechanical cycle. Transition from temporary to permanent shape was quite rapid (2 sec) and at temperatures near body temperature (60 degrees C). Lastly, porous analogues of the biodegradable elastomers were created using a novel porogen - salt leaching technique. Resulting porous elastomers were designed for tissue engineering scaffolds or shape memory foams

SUSTRACCIÓN Y RESTITUCIÓN DE MENORES EN EL DERECHO INTERNACIONAL Y EN EL DERECHO CONSTITUCIONAL MEXICANO

El tema de la sustracción de menores, obliga a hacer referencia a la guarda y custodia, derivada de la figura de la patria potestad, la que vinculada a la organización de la familia, ha sufrido, como esta, importantes variaciones en las últimas décadas, ante lo vertiginoso de los desplazamientos de personas a lo largo y ancho del mundo, con fines laborales, profesionales, académicos, artísticos, financieros, turísticos, empresariales, energéticos, inclusive delincuenciales, -por ejemplo, los terroristas-, y un largo etcétera, provocando la creación de relaciones de todo tipo, en el ámbito familiar: conyugales, concubinarias, de filiación y parentesco, entre personas de diferente nacionalidad, con las consecuencias legales inherentesEl presente capítulo de libro titulado ¨SUSTRACCIÓN Y RESTITUCIÓN DE MENORES EN EL DERECHO INTERNACIONAL Y EN EL DERECHO CONSTITUCIONAL MEXICANO¨ desarrolla una explicación acerca de los menores, abarcando desde el momento en que adquieren la protección del orden jurídico, asi, como quienes lo protegerán en ese orden jurídico, es decir, los padres que ejercen la patria potestad, otorgando de estos últimos una descripción explicativa de la potestad jurídica que se les otorg

SNP-Based Genetic Linkage Map of Soybean Using the SoySNP6K Illumina Infinium BeadChip Genotyping Array

This study reports a high density genetic linkage map based on the ‘Maryland 96-5722’ by ‘Spencer’ recombinant inbred line (RIL) population of soybean [Glycine max (L.) Merr.] and constructed exclusively with single nucleotide polymorphism (SNP) markers. The Illumina Infinium SoySNP6K BeadChip genotyping array produced 5,376 SNPs in the mapping population, with a 96.75% success rate. Significant level of goodness-of-fit for each locus was tested based on the observed vs. expected ratio (1:1). Out of 5,376 markers, 1,465 SNPs fit the 1:1 segregation rate having ≤20% missing data plus heterozygosity among the RILs. Among this 1,456 just 657 were polymorphic between the parents DNAs tested. These 657 SNPs were mapped using the JoinMap 4.0 software and 550 SNPs were distributed on 16 linkage groups (LGs) among the 20 chromosomes of the soybean genome. The total map length was just 201.57 centiMorgans (cM) with an average marker density of 0.37 cM. This is one of the high density SNP-based genetic linkage maps of soybean that will be used by the scientific community to map quantitative trait loci (QTL) and identify candidate genes for important agronomic traits in soybean

How Gaussian competition leads to lumpy or uniform species distributions

A central model in theoretical ecology considers the competition of a range of species for a broad spectrum of resources. Recent studies have shown that essentially two different outcomes are possible. Either the species surviving competition are more or less uniformly distributed over the resource spectrum, or their distribution is 'lumped' (or 'clumped'), consisting of clusters of species with similar resource use that are separated by gaps in resource space. Which of these outcomes will occur crucially depends on the competition kernel, which reflects the shape of the resource utilization pattern of the competing species. Most models considered in the literature assume a Gaussian competition kernel. This is unfortunate, since predictions based on such a Gaussian assumption are not robust. In fact, Gaussian kernels are a border case scenario, and slight deviations from this function can lead to either uniform or lumped species distributions. Here we illustrate the non-robustness of the Gaussian assumption by simulating different implementations of the standard competition model with constant carrying capacity. In this scenario, lumped species distributions can come about by secondary ecological or evolutionary mechanisms or by details of the numerical implementation of the model. We analyze the origin of this sensitivity and discuss it in the context of recent applications of the model.Comment: 11 pages, 3 figures, revised versio

A biogeographic reversal in sexual size dimorphism along a continental temperature gradient

© 2018 The Authors The magnitude and direction of sexual size dimorphism (SSD) varies greatly across the animal kingdom, reflecting differential selection pressures on the reproductive and/or ecological roles of males and females. If the selection pressures and constraints imposed on body size change along environmental gradients, then SSD will vary geographically in a predictable way. Here, we uncover a biogeographical reversal in SSD of lizards from Central and North America: in warm, low latitude environments, males are larger than females, but at colder, high latitudes, females are larger than males. Comparisons to expectations under a Brownian motion model of SSD evolution indicate that this pattern reflects differences in the evolutionary rates and/or trajectories of sex-specific body sizes. The SSD gradient we found is strongly related to mean annual temperature, but is independent of species richness and body size differences among species within grid cells, suggesting that the biogeography of SSD reflects gradients in sexual and/or fecundity selection, rather than intersexual niche divergence to minimize intraspecific competition. We demonstrate that the SSD gradient is driven by stronger variation in male size than in female size and is independent of clutch mass. This suggests that gradients in sexual selection and male–male competition, rather than fecundity selection to maximize reproductive output by females in seasonal environments, are predominantly responsible for the gradient

Predicting the Impact of Climate Change on Threatened Species in UK Waters

Global climate change is affecting the distribution of marine species and is thought to represent a threat to biodiversity. Previous studies project expansion of species range for some species and local extinction elsewhere under climate change. Such range shifts raise concern for species whose long-term persistence is already threatened by other human disturbances such as fishing. However, few studies have attempted to assess the effects of future climate change on threatened vertebrate marine species using a multi-model approach. There has also been a recent surge of interest in climate change impacts on protected areas. This study applies three species distribution models and two sets of climate model projections to explore the potential impacts of climate change on marine species by 2050. A set of species in the North Sea, including seven threatened and ten major commercial species were used as a case study. Changes in habitat suitability in selected candidate protected areas around the UK under future climatic scenarios were assessed for these species. Moreover, change in the degree of overlap between commercial and threatened species ranges was calculated as a proxy of the potential threat posed by overfishing through bycatch. The ensemble projections suggest northward shifts in species at an average rate of 27 km per decade, resulting in small average changes in range overlap between threatened and commercially exploited species. Furthermore, the adverse consequences of climate change on the habitat suitability of protected areas were projected to be small. Although the models show large variation in the predicted consequences of climate change, the multi-model approach helps identify the potential risk of increased exposure to human stressors of critically endangered species such as common skate (Dipturus batis) and angelshark (Squatina squatina)

Dopant imaging of power semiconductor device cross sections

Several Scanning Probe Microscopy (SPM) methods allow to image dopant profiles in a range from 10(14) cm(-3) to 10(19) cm(-3) on semiconducting samples. In our work we present Scanning Capacitance Force Microscopy (SCFM) and Kelvin Probe Force Microscopy (KPFM) experiments performed on cross sections of silicon (Si) and silicon carbide (SiC) power devices and epitaxially grown calibration layers. The contact potential difference (CPD) shows under illumination a reduced influence on surface defect states. In addition results from numerical simulation of these microscope methods are discussed. (C) 2016 Elsevier B.V. All rights reserved

Moose and snowshoe hare competition and a mechanistic explanation from foraging theory

Moose ( Alces alces ) and snowshoe hare ( Lepus americanus ) appear to compete with each other. This was determined using the “natural experiments” of populations found in sympatry and allopatry on islands at Isle Royale National Park, Michigan, and manipulated exclosures. The population densities from these areas are fit to a series of competition models based upon different competitive mechanisms (Schoener 1974a), using non-linear regression techniques. A model of competition for food where the food can be separated into exclusively used and shared categories is found to predict observed densities of moose and hare best. Finally, the competition model's parameters (fraction of food shared and competition coefficients) are shown to agree with values predicted independently from a foraging model.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47750/1/442_2004_Article_BF00396753.pd