Home About us Contact
|
Home About us Contact | ||
|
|
||
American Continent (american + continent)
Selected AbstractsInvasibility of a coastal strip in NE Spain by alien plantsJOURNAL OF VEGETATION SCIENCE, Issue 4 2002Eduardo Sobrino Castroviejo et al. (1986,1999); Tutin et al. (1968,1980) Abstract. The alien plant species and the ecological factors that facilitate their invasion to a coastal strip in the Baix Camp region (Tarragona, NE Spain) were studied. A detailed inventory of the area showed that 20% of the plant species, most of them from the American Continent, were aliens, many of which were strongly invasive. At the habitat level, the relationships between the invasive behaviour and a number of autecological, ecological and habitat variables were analysed by means of logistic analyses. In the best model five variables were related to alien plant invasions: climatic affinity, disturbance of the invaded habitat, route of introduction, soil moisture during summer, and life form. To elucidate the environmental factors that could be responsible for alien plant invasions at a regional scale, the number of alien taxa and the environmental features at 13 localities of the western Mediterranean area were analysed. The warm lowlands, subjected to low annual rainfall and high population density, exhibited the greatest reception capacity for alien plants. It is concluded that various specific environmental features , high mean temperatures, the abundance of riparian systems, the existence of biotopes with favourable water balance which harbour a great richness of alien species and the high human pressure to which the enclave is subjected, combined with the ecological requirements of the alien species and certain species attributes (biotype) can interact at different scales and have caused the over-representation of alien plants. [source] Trance and Shamanic Cure on the South American Continent: Psychopharmacological and Neurobiological InterpretationsANTHROPOLOGY OF CONSCIOUSNESS, Issue 1 2010FRANCOIS BLANC ABSTRACT This article examines the neurobiological basis of the healing power attributed to shamanic practices in the Andes and Brazil in light of the pharmacology of neurotransmitters and the new technological explorations of brain functioning. The psychotropic plants used in shamanic psychiatric cures interfere selectively with the intrinsic neuromediators of the brain. Mainly they may alter: (1) the neuroendocrine functioning through the adrenergic system by controlling stressful conditions, (2) the dopaminergic system in incentive learning and emotions incorporation, (3) the serotoninergic system in modulating behaviors, and mood, and (4) basic functions implied in anxiety or depression. PET scans and functional magnetic resonance imaging studies of hypnotic trance and altered states of consciousness may provide a useful model for the neurophysiological phenomena of shamanic drum-and-dance trance. The reorganization of cortical areas and the direct interconnections between the prefrontal cortex and the dopaminergic reward centers in the limbic system are of particular significance for human social judgment and symbolic processing. Those centers,including the hypothalamus and the amygdala (associated with psychosomatic equilibrium, memory, and emotion) are enhanced. This arousal may be amplified in order to induce a cathartic crisis,the shamanic trance. It is suggested that through this holistic approach the shaman empirically interferes in neurobiological dysfunctions. [source] Biogeography and conservation of the genus Ficus (Moraceae) in MexicoJOURNAL OF BIOGEOGRAPHY, Issue 3 2004Alejandra Serrato Abstract Aim, The main objective of this study is to document the biogeographical patterns, endemism and degree of conservation of the species of Ficus (Moraceae) in Mexico. There are over 750 species of the genus Ficus distributed worldwide, and Mexico practically represents its northernmost limit in the American continent. Detailed studies at regional scales may help to understand the biogeography of large genera such as Ficus. Location, Mexico. Methods, The biogeographical patterns of Mexican Ficus were obtained from information of fig specimens available in two of the main herbaria of Mexico (2140 vouchers), collecting figs throughout this country, and revising the specialized literature. The presence of each species of Ficus was recorded for every one of Mexico's states and several tropical countries of America. Besides, the Mexican territory was divided into cells of 1° × 1° and the presence or absence of all species of the genus was recorded. Rarity of species was classified based on the width of geographic distribution, habitat specificity and population size. Results, A total of 21 species of Ficus occur in Mexico, including six species (28.6%) that are endemic to this country. Five species are included in subgenus Pharmacosycea and 16 species are documented under subgenus Urostigma. Affinities of Ficus flora with other tropical countries in America generally decreased as geographical distances from Mexico increased. Mexican states and cells with highest values of Ficus species richness (both total and endemic species) were located. Ten species, including three endemics, presented a wide distribution. Five species, including two endemics, possess the three attributes of rarity (narrow geographical distribution, high habitat specificity and scarce local populations). Three species of Ficus, including the endemic and very rare Ficuslapathifolia (Liebm.) Miq., are not recorded in any protected area existing in Mexico. Main conclusions, Most of the Mexican Ficus show a great morphological variation and occupy different habitats along their geographic distribution. The biogeographical patterns described here establish a fundamental scenario for ongoing studies on Ficus,pollinator interactions. However, many local populations are considered to be at risk, as there have been significant reductions in the number and size of local populations. Further studies are needed to understand the process of colonization, maintenance and persistence of fig,pollinator mutualism in species with different patterns of geographic distribution. Mexican Ficus require special policies for conservation due to their complex degree of rarity, particularly their geographic distribution in different types of vegetation, ranging from dry scrublands to tropical rain forests. [source] Antiproliferative, cytotoxic and antitumour activity of coumarins isolated from Calophyllum brasilienseJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2007César Ruiz-Marcial Among the eight Calophyllum species found on the American continent, Calophyllum brasiliense is the most widely distributed. Chemical analysis of this species has shown the presence of xanthones with cancer chemopreventive properties and antifungal activity. Recently, three new coumarins with antineoplastic properties have been found. In this study, we have evaluated the biological effects of the antiproliferative activity of coumarins isolated from C. brasiliense on the survival, cell cycle and apoptosis of cells in-vitro and their antitumour effects in mice. The cytological study showed that coumarins from C. brasiliense reduce the survival of BMK cells (baby mouse kidney cells) by inducing apoptosis and, to a lesser degree, necrosis. The cell cycle was arrested in S-phase and the division of BMK cells was inhibited. Coumarins had caused a reduction of experimental tumours in 83% of animals by the end of the treatment. Therefore, coumarins have the potential to be used alone or in combination with other antineoplastic drugs, and they might increase the effectiveness of other treatments for cancer. [source] The credit crunch , the right time for credit unions to strike?LEGAL STUDIES, Issue 1 2009Dr Nicholas Ryder The origins of the cooperative movement can be traced to the Rochdale Society of Equitable Pioneers in 1844, from which similar institutions emerged in Central Europe, the North American continent and the rest of the world. Modern credit unions evolved from these small cooperative societies and have developed into mainstream providers of financial services in many jurisdictions. However, credit unions in the UK have not made a similar impact. There are several factors that have limited their growth , an inadequate legislative framework, an ineffective credit union regulatory system, inappropriate development models, an over-reliance on state subsidies and a disunited movement. The aim of this paper is to re-examine these factors in light of the level of political support provided by the government since 1997. [source] Blood group O alleles in Native Americans: Implications in the peopling of the AmericasAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Benito Estrada-Mena Abstract All major ABO blood alleles are found in most populations worldwide, whereas the majority of Native Americans are nearly exclusively in the O group. O allele molecular characterization could aid in elucidating the possible causes of group O predominance in Native American populations. In this work, we studied exon 6 and 7 sequence diversity in 180 O blood group individuals from four different Mesoamerican populations. Additionally, a comparative analysis of genetic diversity and population structure including South American populations was performed. Results revealed no significant differences among Mesoamerican and South American groups, but showed significant differences within population groups attributable to previously detected differences in genetic drift and founder effects throughout the American continent. Interestingly, in all American populations, the same set of haplotypes O1, O1v, and O1v(G542A) was present, suggesting the following: (1) that they constitute the main genetic pool of the founding population of the Americas and (2) that they derive from the same ancestral source, partially supporting the single founding population hypothesis. In addition, the consistent and restricted presence of the G542A mutation in Native Americans compared to worldwide populations allows it to be employed as an Ancestry informative marker (AIM). Present knowledge of the peopling of the Americas allows the prediction of the way in which the G542A mutation could have emerged in Beringia, probably during the differentiation process of Asian lineages that gave rise to the founding population of the continent. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] New Polynesian Triangle: Rethinking Polynesian migration and development in the PacificASIA PACIFIC VIEWPOINT, Issue 3 2009Manuhuia Barcham Abstract For many Polynesians migration is still framed within a particular spatial context, although on an enlarged scale , one that we have termed the New Polynesian Triangle. With its apexes in the North American continent to the east, Australia in the west and New Zealand in the south, this New Polynesian Triangle encompasses a particular field through which ongoing Polynesian migration and movement continues to occur. Movement within this New Polynesian Triangle is both multidimensional and multidirectional. While it is the movement of economic resources, particularly remittances, that has captured the interest of many agencies operating in the region, we argue that such economic flows are integrally linked with other flows , of goods, ideas, skills and culture , to form a single dynamic system of movement. Importantly, such flows are not uni-directional (from ,rich' to ,poor' countries) as was assumed in times past. In developing ideas on the New Polynesian Triangle, we wish to move away from the dominant Western discourse of the Pacific Ocean as a barrier to development and movement and towards the reclamation of the ocean as a conduit and source of connection and movement for Pacific peoples. [source] Lack of Genetic Structuring among Tropical Brazilian Wood Stork Populations and Low Genetic Differentiation from North American PopulationsBIOTROPICA, Issue 2 2004Cristiano Dosualdo Rocha ABSTRACT The Wood Stork (Mycteria americana) is a wading bird inhabiting subtropical and tropical regions of the American continent. This species is considered endangered in the United States. We compared variability and genetic structuring of nine Brazilian Pantanal subpopulations with an North American population using eight allozyme loci data (MPI, ICD, NSP, EST-D, LDH, PGM, 6PGD, and PEP-A) and four microsatellite loci data (WS1, WS2, WS4, and WS6). Average expected heterozygosity of Pantanal population was similar (0.198 ± 0.065) to that expected for the North American population (0.231 ± 0.066). No significant genetic differentiation was found among Pantanal subpopulations (Fst= 0.012) and low differentiation was detected between Pantanal and North American populations (Fst= 0.023). Lack of differentiation among Pantanal subpopulations may have been due to high gene flow level among birds of neighbor breeding colonies and low natal philopatry. We propose that low differentiation between North and South American populations has arisen either because these populations occupied neighboring regions during late glaciation or because there is a continuous gene flow between them, via Central American or northern South American populations. RESUMO O Cabeça-seca (Mycteria americana) é uma ave aquática habitante das regiões tropicais e subtropicais do continente americano. Essa espécie está ameaçada de extinção nos Estados Unidos. Nós comparamos a variabilidade e a estruturação genética de nove subpopulações brasileiras do Pantanal com as da população norte americana, baseando-se em dados de oito locos alozímicos (MPI, ICD, NSP, EST-D, LDH, PGM, 6PGD, e PEP-A) e em dados de quatro locos de microssatélites (WS1, WS2, WS4, e WS6). A heterozigosidade média esperada para a população do Pantanal (0.198 ± 0.065) foi semelhante á esperada para a população norte americana (0.231 ± 0.066). Não foi encontrada diferenciação genética significativa entre as subpopulaçóes do Pantanal (Fst= 0.012) e baixa diferenciação genética foi detectada entre as populações do Pantanal e a norte americana (.Fst= 0.023). A não diferenciação entre subpopulações do Pantanal pode ser resultante de um alto nível do fluxo génico entre aves de colónias reprodutivas vizinhas e da baixa filopatria natal. Nós propomos que a baixa diferenciação entre as populações norte e sul americanas seja decorrente da ocupaçaTo de regiões vizinhas por essas populações durante a última glaciação ou devido á existéncia de fluxo contínue entre elas, via populações da América Central ou do norte da América do Sul. [source] Molecular clocks keep dispersal hypotheses afloat: evidence for trans-Atlantic rafting by rodentsJOURNAL OF BIOGEOGRAPHY, Issue 2 2010Diane L. Rowe Abstract Aim, In order to resolve disputed biogeographical histories of biota with Gondwanan continental distributions, and to assess the null hypothesis of vicariance, it is imperative that a robust geological time-frame be established. As an example, the sudden and coincident appearance of hystricognath rodents (Rodentia: Hystricognathi) on both the African and South American continents has been an irreconcilable controversy for evolutionary biologists, presenting enigmas for both Gondwanan vicariance and Late Eocene dispersal hypotheses. In an attempt to resolve this discordance, we aim to provide a more robust phylogenetic hypothesis and improve divergence-date estimates, which are essential to assessing the null hypothesis of vicariance biogeography. Location, The primary centres of distribution are in Africa and South America. Methods, We implemented parsimony, maximum-likelihood and Bayesian methods to generate a phylogeny of 37 hystricognath taxa, the most comprehensive taxonomic sampling of this group to date, on the basis of two nuclear gene regions. To increase phylogenetic resolution at the basal nodes, these data were combined with previously published data for six additional nuclear gene regions. Divergence dates were estimated using two relaxed-molecular-clock methods, Bayesian multidivtime and nonparametric rate smoothing. Results, Our data do not support reciprocal monophyly of African and South American lineages. Indeed, Old World porcupines (i.e. Hystricomorpha) appear to be more closely related to New World lineages (i.e. Caviomorpha) than to other Old World families (i.e. Bathyergidae, Petromuridae and Thryonomyidae). The divergence between the monophyletic assemblage of South American lineages and its Old World ancestor was estimated to have occurred c. 50 Ma. Main conclusions, Our phylogenetic hypothesis and divergence-date estimates are strongly at odds with Gondwanan-vicariance isolating mechanisms. In contrast, our data suggest that transoceanic dispersal has played a significant role in governing the contemporary distribution of hystricognath rodents. Molecular-clock analyses imply a trans-Tethys dispersal event, broadly confined to the Late Cretaceous, and trans-Atlantic dispersal within the Early Eocene. Our analyses also imply that the use of the oldest known South American rodent fossil as a calibration point has biased molecular-clock inferences. [source] | |||||||||||||