939 resultados para Non-resourced mating system


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Objective. To synthesise the scientific evidence concerning barriers to health care access faced by migrants. We sought to critically analyse this evidence with a view to guiding policies. Design. A systematic review methodology was used to identify systematic and scoping reviews which quantitatively or qualitatively analysed data from primary studies. The main variables analysed were structural and contextual barriers (health system organisation) as well as individual (patients and providers). The quality of evidence from the systematic reviews was critically appraised. From 2674 reviews, 79 were retained for further scrutiny, and finally 9 met the inclusion criteria. Results. The structural barriers identified were the lack of health insurance and the high cost of drugs (non-universal health system) and organisational aspects of health system (social insurance system and national health system). The individual barriers were linguistic and cultural. None of the reviews provided a quality appraisal of the studies. Conclusions. Barriers to health care for migrants range from entitlement in non-universal health systems to accessibility in universal ones, and determinants of access to the respective health services should be analysed within the corresponding national context. Generate social and institutional changes that eliminate barriers to access to health services is essential to ensure health for all.

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The EU began railway reform in earnest around the turn of the century. Two ‘railway packages’ have meanwhile been adopted amounting to a series of directives and a third package has been proposed. A range of complementary initiatives has been undertaken or is underway. This BEEP Briefing inspects the main economic aspects of EU rail reform. After highlighting the dramatic loss of market share of rail since the 1960s, the case for reform is argued to rest on three arguments: the need for greater competitiveness of rail, promoting the (market driven) diversion of road haulage to rail as a step towards sustainable mobility in Europe, and an end to the disproportional claims on public budgets of Member States. The core of the paper deals respectively with market failures in rail and in the internal market for rail services; the complex economic issues underlying vertical separation (unbundling) and pricing options; and the methods, potential and problems of introducing competition in rail freight and in passenger services. Market failures in the rail sector are several (natural monopoly, economies of density, safety and asymmetries of information), exacerbated by no less than 7 technical and legal barriers precluding the practical operation of an internal rail market. The EU choice to opt for vertical unbundling (with benefits similar in nature as in other network industries e.g. preventing opaque cross-subsidisation and greater cost revelation) risks the emergence of considerable coordination costs. The adoption of marginal cost pricing is problematic on economic grounds (drawbacks include arbitrary cost allocation rules in the presence of large economies of scope and relatively large common costs; a non-optimal incentive system, holding back the growth of freight services; possibly anti-competitive effects of two-part tariffs). Without further detailed harmonisation, it may also lead to many different systems in Member States, causing even greater distortions. Insofar as freight could develop into a competitive market, a combination of Ramsey pricing (given the incentive for service providers to keep market share) and price ceilings based on stand-alone costs might be superior in terms of competition, market growth and regulatory oversight. The incipient cooperative approach for path coordination and allocation is welcome but likely to be seriously insufficient. The arguments to introduce competition, notably in freight, are valuable and many e.g. optimal cross-border services, quality differentiation as well as general quality improvement, larger scale for cost recovery and a decrease of rent seeking. Nevertheless, it is not correct to argue for the introduction of competition in rail tout court. It depends on the size of the market and on removing a host of barriers; it requires careful PSO definition and costing; also, coordination failures ought to be pre-empted. On the other hand, reform and competition cannot and should not be assessed in a static perspective. Conduct and cost structures will change with reform. Infrastructure and investment in technology are known to generate enormous potential for cost savings, especially when coupled with the EU interoperability programme. All this dynamism may well help to induce entry and further enlarge the (net) welfare gains from EU railway reform. The paper ends with a few pointers for the way forward in EU rail reform.

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Highlights: • Since the collapse of the Soviet Union in 1991, Belarus has maintained a largely non-market economic system. This did not prevent rapid growth of its economy over a sustained period up to 2011. However, the period of economic growth in Belarus seems to be over.The factors that underpinned Belarus’s growth, mainly the beneficial external environment, have gradually disappeared. As a result, the country is confronted by the need to start the far-reaching programme of market-oriented economic reforms and macroeconomic stabilisation which it tried to avoid for so long. Reform will not be easy, economically and politically. • The potential hardship facing Belarus could be at least partly cushioned by external assistance, in the first instance from the International Monetary Fund and the World Bank. However, the IMF has relatively fresh memories of the failure of its 2009-10 Stand-By Arrangement (SBA) with Belarus, which provided substantial balance-of payments support, but which was derailed by its too-narrow focus on monetary and fiscal quantitative performance criteria, and by insufficient reform commitment on the Belarusian side. Other donors, such as the European Union, might be reluctant to offer assistance as long as Belarus does not improve its poor human rights record and start some political reforms.

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Cases of evolutionary diversification can be characterized along a continuum from weak to strong genetic and phenotypic differentiation. Several factors may facilitate or constrain the differentiation process. Comparative analyses of replicates of the same taxon at different stages of differentiation can be useful to identify these factors. We estimated the number of distinct phenotypic groups in threespine stickleback populations from nine lakes in Iceland and in one marine population. Using the inferred number of phenotypic groups in each lake, genetic divergence from the marine population, and physical lake and landscape variables, we tested if ecosystem size, approximated by lake size and depth, or isolation from the ancestral marine gene pool predict the occurrence and the extent of phenotypic and genetic diversification within lakes. We find intralacustrine phenotypic diversification to be the rule rather than the exception, occurring in all but the youngest lake population and being manifest in ecologically important phenotypic traits. Neutral genetic data further indicates non-random mating in four out of nine studied lakes, and restricted gene flow between sympatric phenotypic groups in two. Although neither the phenotypic variation nor the number of intralacustrine phenotypic groups were associated with any of our environmental variables, the number of phenotypic traits that were differentiated was significantly positively related to lake size, and evidence for restricted gene flow between sympatric phenotypic groups was only found in the largest lakes where trait specific phenotypic differentiation was highest.

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The planktonic diatom Fragilariopsis kerguelensis plays an important role in the biogeochemical cycles of the Southern Ocean, where remains of its frustules form the largest deposit of biogenic silica anywhere in the world. We assessed the genetic identity of 26 strains, from cells collected at various sites in the Southern Ocean, using three molecular markers, LSU and ITS rDNA and rbcL. The LSU sequences were identical among the tested strains, ITS sequences were highly similar, and only one base pair difference was detected among the rbcL sequences. These results, together with a large number of successful mating experiments demonstrated that the strains belong to a single biological species. We investigated the mating system and life cycle traits of F. kerguelensis. Cell size diminished gradually in clonal strains. Gamete formation only occurred when strains of opposite mating type - within a cell size range of 7-36 µm - were mixed together. Two binucleate gametes were formed in each gametangium and gamete conjugation produced a zygote that had four nuclei and was surrounded by thin siliceous scales. Two out of the four nuclei subsequently degenerated and the zygote expanded to form an auxospore surrounded by a transverse and a longitudinal perizonium. Staining with the fluorochrome PDMPO provided for the first time a clear demonstration that the longitudinal perizonium is formed after auxospore expansion is complete. Initial cells produced within the mature auxospores were 78-101 µm in length. Various authors have shown that the average valve size of F. kerguelensis varies in sediment samples collected in regions and seasons with different primary production regimes and this parameter has thus been proposed as a biological proxy for palaeo-productivity. A better understanding of the life cycle of F. kerguelensis should help the design of future investigations aimed at testing the link between cell size distribution in the natural environment and the role that environmental factors might have in the regulation of population cell size.

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Males of the eastern mosquito fish (Gambusia holbrooki) possess one of the widest reproductively active temperature ranges for any ectotherm, ranging across seasons from at least 18degreesC to 34degreesC. In this study, we tested the ability of male G. holbrooki to acclimate their sustained swimming performance following long-term exposure to 18degreesC or 30degreesC. We also investigated some of the possible physiological mechanisms associated with thermal acclimation responses in swimming performance, including changes in slow muscle fibre size and abundance and the expression of myosin heavy chains (MyHC). We found that U-crit, of 18degreesC-acclimated G. holbrooki was 20% greater at 18degreesC than 30degreesC-acclimated fish, and the Ucrit of the 30degreesC-acclimated group was more than 15% greater at 30degreesC. Slow, fast and intermediate muscle fibres were identified on the basis of their myosin ATPase staining reaction. Although the number of slow and intermediate muscle fibres was similar between groups, the total cross-sectional area of aerobic fibre types was 40% greater in 18degrees-than 30degreesC-acclimated fish, reflecting an increase in the average fibre diameter. An S58 antibody raised against chicken slow skeletal muscle myosin stained a sub-set of the slow fibres identified by myosin ATPase staining. The number of S58-positive muscle fibres was 50% greater in 30degreesC-than 18degreesC-acclimated fish, implying that different MyHCs are being expressed in cold and warm acclimated individuals. Given the sexually coercive mating system of this species, increases in the sustained swimming performance via thermal acclimation may benefit the ability of males to maintain a high rate of sneaky copulations. (C) 2004 Elsevier Ltd. All rights reserved.

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Nine microsatellite loci were developed, and are transferable, across the Madagascan succulents Bryophyllum daigremontianum, Bryophyllum delagoense (mother-of-millions) and their horticultural hybrid (Houghton's), from enriched libraries of the later two species. For B. delagoense, a tetraploid, three to 13 alleles per locus were found for native Madagascan (H-O = 0.4-1.0), and one to nine in invasive Australian (H-O = 0.0-1.0) samples. In addition for 91 Australian samples, only five multilocus genotypes were found (95% of individuals were of two genotypes), suggesting extensive clonality in its introduced range. These loci will be used to examine genetic diversity, hybrid origin and mating system in natural and introduced populations.

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The theoretical impacts of anthropogenic habitat degradation on genetic resources have been well articulated. Here we use a simulation approach to assess the magnitude of expected genetic change, and review 31 studies of 23 neotropical tree species to assess whether empirical case studies conform to theory. Major differences in the sensitivity of measures to detect the genetic health of degraded populations were obvious. Most studies employing genetic diversity (nine out of 13) found no significant consequences, yet most that assessed progeny inbreeding (six out of eight), reproductive output (seven out of 10) and fitness (all six) highlighted significant impacts. These observations are in line with theory, where inbreeding is observed immediately following impact, but genetic diversity is lost slowly over subsequent generations, which for trees may take decades. Studies also highlight the ecological, not just genetic, consequences of habitat degradation that can cause reduced seed set and progeny fitness. Unexpectedly, two studies examining pollen flow using paternity analysis highlight an extensive network of gene flow at smaller spatial scales (less than 10 km). Gene flow can thus mitigate against loss of genetic diversity and assist in long-term population viability, even in degraded landscapes. Unfortunately, the surveyed studies were too few and heterogeneous to examine concepts of population size thresholds and genetic resilience in relation to life history. Future suggested research priorities include undertaking integrated studies on a range of species in the same landscapes; better documentation of the extent and duration of impact; and most importantly, combining neutral marker, pollination dynamics, ecological consequences, and progeny fitness assessment within single studies.

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Despite the typically low population densities and animal-mediated pollination of tropical forest trees, outcrossing and long-distance pollen dispersal are the norm. We reviewed the genetic literature on mating systems and pollen dispersal for neotropical trees to identify the ecological and phylogenetic correlates. The 36 studies surveyed found >90% outcrossed mating for 45 hermaphroditic or monoecious species. Self-fertilization rates varied inversely with population density and showed phylogenetic and geographic trends. The few direct measures of pollen flow (N = 11 studies) suggest that pollen dispersal is widespread among low-density tropical trees, ranging from a mean of 200 m to over 19 km for species pollinated by small insects or bats. Future research needs to examine (1) the effect of inbreeding depression on observed outcrossing rates, (2) pollen dispersal in a wide range of pollination syndromes and ecological classes, (3) and the range of variation of mating system expression at different hierarchical levels, including individual, seasonal, population, ecological, landscape and range wide.

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Female choice based on multiple male traits has been documented in many species but the functions of such multiple traits are still under debate. The satin bowerbird has a polygynous mating system in which males attract females to bowers for mating; females choose mates based on multiple aspects of males and their bowers. In this paper, we demonstrate that females use some cues to decide which males to examine closely and other cues to decide which males to mate with. Female visitation rates to bowers were significantly related to male size and the males' 'solitary' display rates, and, to a lesser extent, to the numbers of bower decorations. After controlling for female visitation rates, it was found that a male's mating success was significantly related to his size and the rate at which he 'painted' his bower with saliva and chewed up plant material.

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All copulations in the eastern mosquitofish, Gambusia holbrooki, are coercive-and-achieved by force. Female G. holbrooki never appear to cooperate with males, but vigorously resist matings at all times. We examined the role of females within a sexually coercive mating system by investigating the ability of female G. holbrooki to resist forced copulations after acclimation to 16 degrees C and 32 degrees C for 4-5 weeks. We also examined burst swimming performance of female G. holbrooki after acclimation, as this trait is likely to underlie a female's ability to resist forced matings. We predicted that if female G. holbrooki indiscriminately resist matings from all males, acclimation would enhance female resistance at their acclimation temperature. However, we found that it did not. We also predicted that if females are able to influence the outcome of mating interactions, acclimation to an optimal thermal environment may induce females to reduce resistance. In support of this prediction, females acclimated at 32 degrees C were able to modify their resistance behaviour between exposure to 16 degrees C and 32 degrees C. The rate of copulations experienced by 32 inverted perpendicular C-acclimated females was 2.5 times greater at 32 degrees C than at 16 degrees C. In addition, acclimation at 32 degrees C significantly enhanced burst swimming performance at 32 degrees C but no effect of acclimation was observed at 16 degrees C. Our results suggest that female G. holbrooki are able to play a greater role in determining the outcome of sexual coercive mating interactions than previously thought. (c) 2006 The Association for the Shidy of Animal Behavioor. Published by Elsevier Ltd. All rights reserved.

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Several behavioral studies of large, gregarious, and sexually dimorphic macropods have shown that males form dominance hierarchies and large males have the highest reproductive success. The bridled nailtail wallaby (Onychogalea fraenata) is a smaller and strongly sexually dimorphic macropod, but is also highly solitary and males do not form dominance hierarchies that are maintained temporally or spatially. Genetic studies of paternity have shown that large males are the most reproductively successful and only one-quarter of males sire offspring at any one time. The aim of this study was to investigate the tactics that males adopt to secure access to females at the time of estrus and to investigate whether females can influence which males have access to them. This study was conducted using 2 wild, free-ranging populations of bridled nailtail wallabies. Females in estrus were located and observed. and the total number of males present, the relative weight rank of each mate, and interactions between individuals were recorded. Females showed a preference for large males and incited male-male competition when the group of males present was large. Unlike other dimorphic macropods, fights among males were rare and were restricted to males of similar size. Large males gained access to females by guarding and following them closely and threatening other males who attempted to gain access. Smaller males spent less time with females, suggesting that small males may leave multimale groups in an attempt to locate unguarded females. Given the solitary nature of this species and the lack of a stable dominance hierarchy to influence male reproductive success. mate searching and mate guarding may be important male reproductive tactics in this species.

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In the analysis and prediction of many real-world time series, the assumption of stationarity is not valid. A special form of non-stationarity, where the underlying generator switches between (approximately) stationary regimes, seems particularly appropriate for financial markets. We introduce a new model which combines a dynamic switching (controlled by a hidden Markov model) and a non-linear dynamical system. We show how to train this hybrid model in a maximum likelihood approach and evaluate its performance on both synthetic and financial data.

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The dramatic effects of brain damage can provide some of the most interesting insights into the nature of normal cognitive performance. In recent years a number of neuropsychological studies have reported a particular form of cognitive impairment where patients have problems recognising objects from one category but remain able to recognise those from others. The most frequent ‘category-specific’ pattern is an impairment identifying living things, compared to nonliving things. The reverse pattern of dissociation, i.e., an impairment recognising and naming nonliving things relative to living things, has been reported albeit much less frequently. The objective of the work carried out in this thesis was to investigate the organising principles and anatomical correlates of stored knowledge for categories of living and nonliving things. Three complementary cognitive neuropsychological research techniques were employed to assess how, and where, this knowledge is represented in the brain: (i) studies of normal (neurologically intact) subjects, (ii) case-studies of neurologically impaired patients with selective deficits in object recognition, and (iii) studies of the anatomical correlates of stored knowledge for living and nonliving things on the brain using magnetoencephalography (MEG). The main empirical findings showed that semantic knowledge about living and nonliving things is principally encoded in terms of sensory and functional features, respectively. In two case-study chapters evidence was found supporting the view that category-specific impairments can arise from damage to a pre-semantic system, rather than the assumption often made that the system involved must be semantic. In the MEG study, rather than finding evidence for the involvement of specific brain areas for different object categories, it appeared that, when subjects named and categorised living and nonliving things, a non-differentiated neural system was involved.