RESUMO
Biodiversity studies comprise the systematic examination of the full array of different kinds of organisms together with the technology by which the diversity can be maintained and used for the benefit of humanity. Current basic research at the species level focuses on the process of species formation, the standing levels of species numbers in various higher taxonomic categories, and the phenomena of hyperdiversity and extinction proneness. The major practical concern is the massive extinction rate now caused by human activity, which threatens losses in the esthetic quality of the world, in economic opportunity, and in vital ecosystem services.
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Predation on lupine flowers by larvae of a lycaenid butterfly was studied by comparison of inflorescences exposed to and protected from infestation, and by comparison of lupine populations exposed to different degrees of attack. The lycaenids caused striking reduction in seed set, indicating that this small herbivore could act as a potent selectie agent in lupine populations.
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Larvae of Euptychia westwoodi feed on Selaginella, a lycopsid. This is the first feeding record in the Satyrinae outside the monocotyledons and one of the few records of a butterfly feeding on other than a seed plant. Clues to possible evolutionary origins of this habit are found in the oviposition behavior of other Euptychia species.
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Genetically distinct populations are an important component of biodiversity. This work estimates the number of populations per area of a sample of species from literature on population differentiation and the average range area of a species from a sample of distribution maps. This yields an estimate of about 220 populations per species, or 1.1 to 6.6 billion populations globally. Assuming that population extinction is a linear function of habitat loss, approximately 1800 populations per hour (16 million annually) are being destroyed in tropical forests alone.
Assuntos
Ecossistema , Genética Populacional , Animais , Matemática , Plantas , Polimorfismo de Fragmento de Restrição , Densidade DemográficaRESUMO
Globally, tropical deforestation releases 20 to 30% of anthropogenic greenhouse gases. Conserving forests could reduce emissions, but the cost-effectiveness of this mechanism for mitigation depends on the associated opportunity costs. We estimated these costs from local, national, and global perspectives using a case study from Madagascar. Conservation generated significant benefits over logging and agriculture locally and globally. Nationally, however, financial benefits from industrial logging were larger than conservation benefits. Such differing economic signals across scales may exacerbate tropical deforestation. The Kyoto Protocol could potentially overcome this obstacle to conservation by creating markets for protection of tropical forests to mitigate climate change.
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Conservação dos Recursos Naturais/economia , Ecossistema , Árvores , Agricultura , Carbono , Análise Custo-Benefício , Países Desenvolvidos , Países em Desenvolvimento , Efeito Estufa , Indústrias , MadagáscarRESUMO
Subfreezing temperatures, low light levels, and high doses of ionizing and ultraviolet radiation extending for many months after a large-scale nuclear war could destroy the biological support systems of civilization, at least in the Northern Hemisphere. Productivity in natural and agricultural ecosystems could be severely restricted for a year or more. Postwar survivors would face starvation as well as freezing conditions in the dark and be exposed to near-lethal doses of radiation. If, as now seems possible, the Southern Hemisphere were affected also, global disruption of the biosphere could ensue. In any event, there would be severe consequences, even in the areas not affected directly, because of the interdependence of the world economy. In either case the extinction of a large fraction of the Earth's animals, plants, and microorganisms seems possible. The population size of Homo sapiens conceivably could be reduced to prehistoric levels or below, and extinction of the human species itself cannot be excluded.
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Meio Ambiente , Guerra Nuclear , Animais , Atmosfera , Clima , Humanos , Fotossíntese , Radiação Ionizante , Cinza Radioativa , Luz Solar , Temperatura , Raios UltravioletaRESUMO
Ecosystems are capital assets: When properly managed, they yield a flow of vital goods and services. Relative to other forms of capital, however, ecosystems are poorly understood, scarcely monitored, and--in many important cases--undergoing rapid degradation. The process of economic valuation could greatly improve stewardship. This potential is now being realized with innovative financial instruments and institutional arrangements.
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Conservação dos Recursos Naturais/economia , Ecossistema , Austrália , Comércio , Costa Rica , Indústrias , Investimentos em SaúdeRESUMO
Twenty-one populations of the checkerspot butterfly, Euphydryas editha, and ten populations of Euphydryas chalcedona were sampled for genetic variation at eight polymorphic enzyme loci. Both species possessed loci that were highly variable from population to population and loci that were virtually identical across all populations sampled. Our data indicate that the neutrality hypothesis is untenable for the loci studied, and therefore selection is indicated as the major factor responsible for producing these patterns. Thorough ecological work allowed gene flow to be ruled out (in almost all instances) as a factor maintaining similar gene frequencies across populations. The Lewontin-Krakauer test indicated magnitudes of heterogeneity among standardized variances of gene frequencies inconsistent with the neutrality hypothesis. The question of whether or not to correct this statistic for sample size is discussed. Observed equitability of gene frequencies of multiple allelic loci was found to be greater than that predicted under the neutrality hypothesis. Genetic differentiation persisting through two generations was found between the one pair of populations known to exchange significant numbers of individuals per generation. Two matrices of genetic distance between populations, based on the eight loci sampled, were found to be significantly correlated with a matrix of environmental distance, based on measures of fourteen environmental parameters. Correlations between gene frequencies and environmental parameters, results of multiple regression analysis, and results of principle component analysis showed strong patterns of association and of "explained" variation. The correlation analyses suggest which factors might be further investigated as proximate selective agents.
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Borboletas/fisiologia , Frequência do Gene , Lepidópteros/fisiologia , Polimorfismo Genético , Animais , Eletroforese em Gel de Amido , Enzimas/análise , Variação Genética , Genética Populacional , Seleção GenéticaRESUMO
Estimates of allele frequencies at six polymorphic loci were collected over eight generations in two populations of Euphydryas editha. We have estimated, in addition, the effective population size for each generation for both populations with results from mark-recapture and other field data. The variation in allele frequencies generated by random genetic drift was then studied using computer simulations and our direct estimates of effective population size. Substantial differences between observed values and computer-generated expected values assuming drift alone were found for three loci (Got, Hk, Pgi) in one population. These observations are consistent with natural selection in a variable environment.
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Alelos , Borboletas/genética , Frequência do Gene , Variação Genética , Lepidópteros/genética , Animais , Borboletas/enzimologia , Enzimas/genética , Feminino , Fertilidade , Masculino , Matemática , Modelos Genéticos , Polimorfismo Genético , ReproduçãoRESUMO
A simple, globally aggregated, stochastic-simulation model was constructed to examine the effects of rapid climatic change on agriculture and the human population. The model calculates population size and the production, consumption and storage of grain under different climate scenarios over a 20-year projection time. In most scenarios, either an optimistic baseline annual increase of agricultural output of 1.7% or a more pessimistic appraisal of 0.9% was used. The rate of natural increase of the human population exclusive of excess hunger-related deaths was set as 1.7% per year and climatic changes with both negative and positive impacts on agriculture were assessed. Analysis of the model suggests that the number of hunger-related deaths could double (with reference to an estimated 200 million deaths in the past two decades) if grain production keeps pace with population growth but climatic conditions are unfavourable. If the rate of increase in grain production is about half that of population growth, the number of hunger-related deaths could increase about fivefold (over past levels); the impact of climatic change is relatively small under this imbalance. Even favourable climatic changes that enhance agricultural production may not prevent a fourfold increase in deaths (over past levels) under scenarios where population growth outpaces production by about 0.8% per annum. These results may foreshadow a fundamental change where, for the first time, absolute global food deficits compound inequities in food production and distribution in causing famine. The model also highlights the effectiveness of reducing population growth rates as a strategy for minimizing the impact of global climate change and maintaining food supplies for everyone.