990 resultados para native populations
Resumo:
Coastal birds are an integral part of coastal ecosystems, which nowadays are subject to severe environmental pressures. Effective measures for the management and conservation of seabirds and their habitats call for insight into their population processes and the factors affecting their distribution and abundance. Central to national and international management and conservation measures is the availability of accurate data and information on bird populations, as well as on environmental trends and on measures taken to solve environmental problems. In this thesis I address different aspects of the occurrence, abundance, population trends and breeding success of waterbirds breeding on the Finnish coast of the Baltic Sea, and discuss the implications of the results for seabird monitoring, management and conservation. In addition, I assess the position and prospects of coastal bird monitoring data, in the processing and dissemination of biodiversity data and information in accordance with the Convention on Biological Diversity (CBD) and other national and international commitments. I show that important factors for seabird habitat selection are island area and elevation, water depth, shore openness, and the composition of island cover habitats. Habitat preferences are species-specific, with certain similarities within species groups. The occurrence of the colonial Arctic Tern (Sterna paradisaea) is partly affected by different habitat characteristics than its abundance. Using long-term bird monitoring data, I show that eutrophication and winter severity have reduced the populations of several Finnish seabird species. A major demographic factor through which environmental changes influence bird populations is breeding success. Breeding success can function as a more rapid indicator of sublethal environmental impacts than population trends, particularly for long-lived and slowbreeding species, and should therefore be included in coastal bird monitoring schemes. Among my target species, local breeding success can be shown to affect the populations of the Mallard (Anas platyrhynchos), the Eider (Somateria mollissima) and the Goosander (Mergus merganser) after a time lag corresponding to their species-specific recruitment age. For some of the target species, the number of individuals in late summer can be used as an easier and more cost-effective indicator of breeding success than brood counts. My results highlight that the interpretation and application of habitat and population studies require solid background knowledge of the ecology of the target species. In addition, the special characteristics of coastal birds, their habitats, and coastal bird monitoring data have to be considered in the assessment of their distribution and population trends. According to the results, the relationships between the occurrence, abundance and population trends of coastal birds and environmental factors can be quantitatively assessed using multivariate modelling and model selection. Spatial data sets widely available in Finland can be utilised in the calculation of several variables that are relevant to the habitat selection of Finnish coastal species. Concerning some habitat characteristics field work is still required, due to a lack of remotely sensed data or the low resolution of readily available data in relation to the fine scale of the habitat patches in the archipelago. While long-term data sets exist for water quality and weather, the lack of data concerning for instance the food resources of birds hampers more detailed studies of environmental effects on bird populations. Intensive studies of coastal bird species in different archipelago areas should be encouraged. The provision and free delivery of high-quality coastal data concerning bird populations and their habitats would greatly increase the capability of ecological modelling, as well as the management and conservation of coastal environments and communities. International initiatives that promote open spatial data infrastructures and sharing are therefore highly regarded. To function effectively, international information networks, such as the biodiversity Clearing House Mechanism (CHM) under the CBD, need to be rooted at regional and local levels. Attention should also be paid to the processing of data for higher levels of the information hierarchy, so that data are synthesized and developed into high-quality knowledge applicable to management and conservation.
Resumo:
The health of older immigrants can have important consequences for needed social support and demands placed on health systems. This paper examines health differences between immigrants and the nativeborn populations aged 50 years and older in 11 European countries. We examine differences in functional ability, disability, disease presence and behavioral risk factors, for immigrants and non-immigrants using data from the Survey of Health, Aging and Retirement in Europe (SHARE) database. Among the 11 European countries, migrants generally have worse health than the native population. In these countries, there is a little evidence of the “healthy migrant” at ages 50 years and over. In general, it appears that growing numbers of immigrants may portend more health problems in the population in subsequent years.
Resumo:
The Argentine ant, Linepithema humile, is a world-wide invasive ant species. Its presence has a strong negative impact on ant diversity. The present study attempts to highlight the reasons for the coexistence of this highly dominant species with Plagiolepis pygmaea, the only native ant species that has proved able to resist the invasion in a natural ecosystem in the north-east of the Iberian Peninsula. To quantify the aggressiveness level of both species we performed aggressiveness tests on workers in different areas: a) Argentine ant workers from areas with P. pygmaea, b) Argentine ant workers from areas without P. pygmaea, c) P. pygmaea from a non-invaded area and d) P. pygmaea from an invaded area. We also confronted Argentine ant workers with P. pallidula and T. nigerrimum. These aggressiveness tests showed that the coexistence of these two species of ants was not due to a habituation process, since the aggressiveness level observed between the four kinds of confrontations were fairly similar. We also found a lack of aggressiveness between Argentine ant workers and P. pygmaea, and highly submissive behavior in the latter when confronted with the invader. The peaceful character of P. pygmaea together with its markedly submissive behavior may be the main factors behind the coexistence of these species in the study area
Resumo:
This article carries out an empirical examination of the origin of the differences between immigrant and native-born wage structures in the Spanish labour market. Especial attention is given in the analysis to the role played by occupational and workplace segregation of immigrants. Legal immigrants from developing countries exhibit lower mean wages and a more compressed wage structure than native-born workers. By contrast, immigrants from developed countries display higher mean wages and a more dispersed wage structure. The main empirical finding is that the disparities in the wage distributions for the native-born and both groups of immigrants are largely explained by their different observed characteristics, with a particularly important influence in this context of workplace and, particularly, occupational segregation.
Resumo:
This study is focused on the dominance exerted by the invasive Argentine ant over native ants in a coastal Mediterranean area. Theimpact of this invasive ant on native ant assemblages and its consequences on total ant biomass and on the intensity of habitat explorationwere evaluated. Foraging ants were observed and their trajectories recorded during 5-minute periods in two study zones, one invaded andthe other non-invaded. Ant species detected, ant worker abundance, ant biomass and the intensity of soil surface searching done by antswere compared between the two zones. The Argentine ant invasion provoked a drastic reduction of the ant species richness. Apparentlyonly one native ant species is able to coexist with the Argentine ant, the cryptic Plagiolepis pygmaea. Ant worker abundance was also modified after the invasion: the number of Argentine ant workers detected, which represented 92% of the invaded zone, was two times higher than the number of native ant workers detected in the non-invaded zone. The total ant biomass was inversely affected, becoming four times lower in the invaded zone highly dominated by Linepithema humile. The higher number of Argentine ant workers and their fast tempo of activity implied an alteration of the intensity of soil surface searching: scanning by the Argentine ants in the invaded zone was higher than that done by the native ants in the non-invaded zone, and the estimated time for a complete soil surface scan was 64 minutes in the invaded zone and 108 minutes in the non-invaded zone. Consequently, resources will be discovered faster by ants in the invaded zone than in the non-invaded zone. The increase of the mean temperature and the decrease of the relative humidity from May to August reduced the ant activity in the two study zones but this reduction was greater in the invaded zone
Resumo:
First record of the alien pest Rhaponticum repens (Compositae) in the Iberian Peninsula.- Rhaponticum repens is reported for the first time for the flora of the Iberian Peninsula. The species is native from Central Asia and has become invasive in Argentina, Canada, Europe and the USA. It was detected for the first time in abandoned fields from Vilablareix, near the city of Girona (Catalonia, Spain) and in the valley of the Vinalopó in Alicante (Valencia, Spain), where it was collected as early as in 1959 but misdentified. Molecular data, based on nrDNA region ITS, suggest that the reported populations may be closely related to plants from the United States. Due to the extremely noxious character of the species and the possible relationship of Spanish plants with the invasive American populations, some kind of monitoring is recommended
Resumo:
Ilex paraguariensis is a native plant in Southern Brazil, whose leaves are utilized in beverages such as chimarrão and tererê. This study investigated variations of total methylxanthines in leaves from two Ilex populations collected at one-month intervals over the course of one year. The levels varied from 1.92 to 10.37 mg/g (Ijuí) and 1.77 to 9.17 mg/g (Santa Maria). Statistical analysis indicated a significative variation in the contents of all samples analysed, confirming seasonal fluctuations. These results show that the period of harvest might decisively influence the organoleptic characteristics of raw material used in industry and therefore in commercial products.
Resumo:
The wave-of-advance model has been previously applied to Neolithic human range expansions, yielding good agreement to the speeds inferred from archaeological data. Here, we apply it for the first time to Palaeolithic human expansions by using reproduction and mobility parameters appropriate to hunter-gatherers (instead of the corresponding values for preindustrial farmers). The order of magnitude of the predicted speed is in agreement with that implied by the AMS radiocarbon dating of the lateglacial human recolonization of northern Europe (14.2–12.5 kyr BP). We argue that this makes it implausible for climate change to have limited the speed of the recolonization front. It is pointed out that a similar value for the speed can be tentatively inferred from the archaeological data on the expansion of modern humans into the Levant and Europe (42–36 kyr BP)
Resumo:
Pyrrolizidine alkaloids (PAs) are N-based plant secondary metabolites that function as chemical defenses against vertebrate and invertebrate herbivores. PAs can be highly variable at intraspecific level, both in their absolute and relative concentrations. Changes in the chemical composition of exotic plants when they invade a new environment have been poorly explored. Here we studied the biogeographical variation on PAs in Senecio pterophorus (Asteraceae) in the native region in Eastern South Africa, an expanded region in Western South Africa, and two introduced regions in Australia and Europe. PAs in S. pterophorus were represented by the highly toxic 1,2-unsaturated PAs and the less toxic 1,2-saturated PAs. Our results show a change in the plant chemical composition after invasion. Total PAs concentrations were highest in Australia compared to any other region. Plants from Europe contained the highest relative concentrations of 1,2-saturated PAs. The positive correlation between the chemical and the genetic distances estimated between populations suggests that the chemical profiles in the non-native regions were related to the plant dispersal routes. The decrease in the chemical diversity and the change in the absolute PAs concentrations in S. pterophorus after invasion may have consequences in the interactions between plants and herbivores in the novel habitats.
Resumo:
Brazil is one of the largest producers and consumers of charcoal in the world. About 50% of its charcoal comes from native forests, with a large part coming from unsustainable operations. The anatomic identification of charcoal is subjective; an instrumental technique would facilitate the monitoring of forests. This study aimed to verify the feasibility of using medium and near infrared reflectance spectroscopy to discriminate native (ipê) from plantation charcoals (eucalyptus). Principal Components Analysis, followed by Discriminant Factorial Analysis formed two different groups indicated by Mahalanobis distances of 40.6 and 80.3 for near and mid infrared, respectively. Validation of the model showed 100% efficacy.