Showing papers by "Universidade Federal de Viçosa published in 2004"
TL;DR: The ecophysiological constraints on the production of the arabica and robusta coffee under shading or full sunlight are reviewed and the relationships between gas exchange performance and key environmental factors are emphasized.
403 citations
TL;DR: Techniques are presented to detect unexpected pleiotropic changes in such instances despite very subtle changes in overall metabolism, especially when gene suppression or knockout is targeted to isoenzymes or gene families.
Abstract: Current efforts aim to functionally characterize each gene in model plants. Frequently, however, no morphological or biochemical phenotype can be ascribed for antisense or knock-out plant genotypes. This is especially the case when gene suppression or knockout is targeted to isoenzymes or gene families. Consequently, pleiotropic effects and gene redundancy are responsible for phenotype resistance. Here, techniques are presented to detect unexpected pleiotropic changes in such instances despite very subtle changes in overall metabolism. The method consists of the relative quantitation of >1,000 compounds by GC/time-of-flight MS, followed by classical statistics and multivariate clustering. Complementary to these tools, metabolic networks are constructed from pair-wise analysis of linear metabolic correlations. The topology of such networks reflects the underlying regulatory pathway structure. A differential analysis of network connectivity was applied for a silent potato plant line suppressed in expression of sucrose synthase isoform II. Metabolic alterations could be assigned to carbohydrate and amino acid metabolism even if no difference in average metabolite levels was found.
385 citations
TL;DR: In this article, the effects of salinity on some growth and physiological parameters in algarrobo seedlings were investigated, and the results suggest that glycinebetaine enhancement may be important for osmotic adjustment in prosopis alba under salinity stress.
Abstract: Prosopis alba (algarrobo) is one of the most important salt-tolerant legumes used in the food and furniture industries. The effects of salinity on some growth and physiological parameters in algarrrobo seedlings were investigated. 17-Day-old seedlings were subjected to three salt treatments by adding NaCl to the growth medium in 50 mmol.L-1 increments every 24 h until the final concentrations of 0, 300 and 600 mmol.L-1 were reached. Only the highest NaCl concentration affected all of the considered parameters. Thus, 600 mmol.L-1 NaCl caused a significant reduction in root and shoot growth, but an increase in the root/shoot ratio. Leaf relative water content, nitrate content and nitrate reductase activity in leaves and roots were also decreased. At 300 and 600 mmol.L-1, the glycinebetaine content was significantly increased in both leaves and roots but this was not found for proline content. Total soluble carbohydrates increased only in roots. The results suggest that glycinebetaine enhancement may be important for osmotic adjustment in Prosopis alba under salinity stress.
237 citations
TL;DR: It is concluded that pasture decline is hastened by increasing stocking rates because of these losses of N and the decrease in N and other nutrients available for grass growth.
237 citations
TL;DR: Rhizobacteria B101R, B212R, and A068R, selected as inducers of systemic resistance against Pseudomonas syringae pv.
224 citations
TL;DR: The hypothesis that the presence of forest remnants increases coffee agricultural productivity through an increase in pollination is tested, based on the assumption that areas of preservation of native forest required by Brazilian law provide pollinators to local agroecosystems.
Abstract: Ecosystem services are natural functions of an ecosystem that can be, secondarily, used for the benefit of humans. A recent estimate showed that ecosystem services equal, on average, 33 trillion dollars a year, with pollination being responsible for 112 billions dollars. The alteration of natural systems and the loss of pollinating species have caused a decrease in many crops' productivity. The objective of this work is to evaluate the pollination as an ecological service in agriculture, testing the hypothesis that the presence of forest remnants increases coffee agricultural productivity through an increase in pollination. This argument is based on the assumption that areas of preservation of native forest required by Brazilian law provide pollinators to local agroecosystems. Fruit production was compared among three different planting regimes: agrosilviculture, and conventional monoculture with and without preserved forest remnants nearby. The average flower production by branch was different among the farms and was not related to the planting methods. The first flowering was larger than the second, representing 81–98% of the flowers' total production. The farms near forest fragments had an increase of 14.6% in production that can be related to the pollinating services.
223 citations
TL;DR: In this paper, the polyaniline (PANI) bases can be classified in three distinct oxidation states: leucoemeraldine (LB), the totally reduced form, emeraldine (EB), the half oxidized form, and pernigraniline, the totally oxidised form.
205 citations
TL;DR: Sera from seven horses and two dogs contained antibodies specific for R. rickettsii, and one dog serum had antibodies against a Rickettsia species very closely related to R. africae, which may have been caused by infection with the recently identified COOPERI strain.
Abstract: In serum samples obtained from all the healthy humans, horses, dogs, and donkeys present on three farms in the Pedreira Municipality, an endemic area for Brazilian spotted fever, an indirect immunofluorescence assay (IFA) detected antibodies against Rickettsia rickettsii in 17 (77.3%) horses, 5 (31.3%) dogs (titers ranging from 64 to 4,048), and none of 4 donkeys or 50 humans. Five canine and eight equine sera with high antibody titers to R. rickettsii were also tested by IFA against R. bellii, R. akari, and R. africae antigens. Sera from two horses and two dogs that showed similar high antibody titers against two rickettsial antigens were evaluated after cross-absorption. Sera from seven horses and two dogs contained antibodies specific for R. rickettsii, and one dog serum had antibodies against a Rickettsia species very closely related to R. africae. The latter may have been caused by infection with the recently identified COOPERI strain.
161 citations
TL;DR: Droughttolerant clones were better able to maintain their leaf water status than drought-sensitive clones after withholding irrigation, and a general link between protection against oxidative stress with differences in clonal tolerance to drought was not observed.
157 citations
TL;DR: The sunnhemp stood out in the phytomass yield, being 108% greater than the spontaneous vegetation and 31% superior to millet, and the BNF was 61% in the intercropping and 57% in sole cropping, being an excellent strategy for increasing soil nitrogen.
Abstract: O objetivo deste trabalho foi avaliar os efeitos dos cultivos isolado e consorciado dos adubos verdes de verao crotalaria (Crotalaria juncea) e milheto (Pennisetum americanum) na producao de fitomassa, nos teores e acumulo de nutrientes e na fixacao biologica de nitrogenio (FBN). O delineamento experimental adotado foi blocos ao acaso, com quatro repeticoes, em que os tratamentos constaram dos adubos verdes crotalaria, milheto, crotalaria + milheto e vegetacao espontânea. A crotalaria apresentou maior producao de fitomassa, que foi 108% maior que a da vegetacao espontânea e 31% superior a do milheto. No consorcio crotalaria + milheto, a leguminosa contribuiu com 65% da massa de materia seca total. A presenca da crotalaria resultou em maiores teores de N e Ca, enquanto o milheto e as ervas espontâneas apresentaram maiores teores de potassio. O acumulo de P e Mg foi fortemente influenciado pela producao de fitomassa, atingindo valores elevados com a presenca da crotalaria, ao passo que o acumulo de N e Ca resultou tanto dos maiores teores quanto da maior producao de fitomassa nos tratamentos com a leguminosa. A FBN foi 61% na leguminosa quando consorciada e 57% quando isolada, incorporando ao solo via FBN 89 e 173 kg/ha de N, respectivamente, constituindo-se excelente estrategia de incremento de N ao solo.
127 citations
TL;DR: Monitoring of de-fruited coffee trees in the field found changes in A appeared to be largely due to stomatal limitations in the active growing season, with non-stomatal ones prevailing in the slow growth period, and foliar carbohydrates seemed not to have contributed appreciably to changes in growth rates and photosynthesis.
TL;DR: Some selected traits (leaf area, crown architecture, water-use efficiency and carbon isotope discrimination, water relations and root characteristics), which may be explored in breeding programmes to tolerance to drought stress in arabica and robusta coffee are reviewed.
Abstract: This paper briefly reviews some selected traits (leaf area, crown architecture, water-use efficiency and carbon isotope discrimination, water relations and root characteristics), which may be explored in breeding programmes to tolerance to drought stress in arabica and robusta coffee.
TL;DR: It is suggested that a higher diversity of shade trees will help to maintain high parasitoid levels and, in consequence, higher levels of natural enemies of cacao pests, particularly in the warmer seasons.
TL;DR: The quality of diagnosis of canine epidemic surveys is analyzed against the backdrop of a visceral leishmaniasis epidemic in Belo Horizonte, Minas Gerais State from 1993 to 1997 to evaluate the effectiveness of the Kala Azar Control Program.
Abstract: In Brazil, visceral leishmaniasis poses a serious endemic and epidemic problem. In recent years the disease has spread to several States that had not previously reported any human or animal cases. For canine surveys, the Ministry of Health currently recommends use of the indirect immunofluorescence assay (IIF), with a sensitivity of 90-100% and specificity of 80%. Use of IIF may decrease the effectiveness of the Kala Azar Control Program by not detecting, and thus failing to sacrifice, false-negative infected animals. On the other hand, the program incorrectly identifies and leads to the unwarranted sacrifice of false-positive uninfected animals. Such uncertainties have already led to disagreement over the Program's objectives, such as the recommendation by some veterinarians that infected animals be treated. This work analyzes the quality of diagnosis of canine epidemic surveys against the backdrop of a visceral leishmaniasis epidemic in Belo Horizonte, Minas Gerais State, from 1993 to 1997.
01 Jan 2004
TL;DR: In this article, the adjustment of g nonlinear regression equations and the likelihood ratio test with χ approximation in order to test model identity were discussed, and the approximations given by F and χ test statistics in a simulation study were compared.
Abstract: We considerer the adjustment of g nonlinear regression equations and the likelihood ratio test with χ approximation in order to test model identity, and we also compare the approximations given by F and χ test statistics in a simulation study. For sufficiently large data sets (N ≥ 120) we found the two approximations to perform roughly the same. For smaller sample sizes the F statistic approximation should be preferred since it yielded smaller type I error rates for N values investigated.
TL;DR: Coffea arabica plants in agroforestry system had less branch growth and leaf production, more persistent and larger leaves, and presented earlier flowering, with a smaller number of productive nodes and flower buds, leading to smaller berry yield than plants in monoculture system.
Abstract: This research compared coffee plants (Coffea arabica L.) grown in an agroforestry and monoculture systems. Data were collected during two years, on vegetative growth, reproductive development, nutritional status and yield of coffee, besides monitoring air temperature and the tree growth. All trees in agroforestry system increased in growth, resulting in a reduction in the magnitude of the diurnal temperature variation and also maximum temperature. Coffee plants in agroforestry system had less branch growth and leaf production, more persistent and larger leaves, and presented earlier flowering, with a smaller number of productive nodes and flower buds, leading to smaller berry yield than plants in monoculture system. In both systems, the coffee plants showed adequate leaf nutrient levels, except for P and K. The yield of 2443 kg ha-1 of coffee from the monoculture was greater than 515 kg ha-1 of coffee from the agroforestry system.
TL;DR: It is shown that proportional sampling can detect species–area relationships (SARs) more effectively than uniform sampling and the proposed model, together with proportional sampling, allowed the distinction between sampling effects and other mechanisms.
Abstract: Aim In this paper we aim to show that proportional sampling can detect species–area relationships (SARs) more effectively than uniform sampling. We tested the contribution of alpha and beta diversity in ant communities as explanations for the SAR.
Location Tropical forest remnants in Vicosa, Minas Gerais, Brazil (20 °45′ S, 42 °50′ W).
Methods We sampled 17 forest remnants with proportional sampling. To disentangle sampling effects from other mechanisms, species richness was fitted in a model with remnant size, number of samples (sampling effects) and an interaction term.
Results A SAR was observed independent of the number of samples, discarding sampling effects. Alpha diversity was not influenced by remnant size, and beta diversity increased with remnant size; evidence to the fact that habitat diversity within remnants could be the dominant cause of the SAR. Such a relationship between beta diversity and remnant area may have also arisen due to the combined effects of territoriality and aggregation of ant species.
Main conclusions The proposed model, together with proportional sampling, allowed the distinction between sampling effects and other mechanisms.
TL;DR: An improvement in the conditions of the area for the support of more advanced ecological groups in the successional scale is suggested, pointing out a tendency for decreasing importance of these ecological groups.
Abstract: O trabalho foi realizado no municipio de Vicosa (20 o45'S e 42 o07'W), no sudeste do Estado de Minas Gerais. O objetivo foi analisar as alteracoes ocorridas no estande entre os levantamentos realizados em 1984 e 1998. Para tanto, as especies foram classificadas em tres grupos ecologicos: pioneiras, secundarias iniciais e secundarias tardias. Tambem comparou-se a variacao ocorrida na distribuicao diametrica e na densidade absoluta. As comparacoes foram analisadas estatisticamente, sendo utilizado o teste "t" de Student, o teste de qui-quadrado (chi2). O estande estava composto por nove pioneiras, 56 secundarias iniciais e 29 secundarias tardias. Analisando as diferencas das medias dos numeros de individuos das secundarias iniciais, exceto Plinia glomerata (Berg.) Amshoff e Sorocea bonplandii (Daill.) Burger. Lanjow & Boer, nao foi observado estatisticamente acrescimo na densidade absoluta. A mesma situacao pode ser observada para as especies pioneiras, nao havendo excecoes. Essas constatacoes revelam tendencia de reducao da importância desses grupos, ao passo que a unica secundaria tardia (Protium warmingianum March.) que pode ser analisada, obteve estatisticamente aumento de sua densidade absoluta. Esses fatos demonstram melhoria nas condicoes de suporte da area para os grupos ecologicos mais avancados na escala sucessional.
TL;DR: In this paper, the authors discuss the endocrine and metabolic role of each adipose tissue compartment, by way to assess their contribution to the complications linked to obesity and diabetics.
Abstract: The adipose tissue is a dynamic organ that secrets several factors, denominated adipokines. They are associated, directly or indirectly, in a process that contributes to atherosclerosis, hypertension, insulinic resistance and diabetes type 2, dyslipidemias, presenting the link between adiposity, metabolic syndrome and cardiovascular diseases. In the obesity, body fat depots are increased, presenting eventual elevation in the adipokines expression and secretion. The different fat depots, visceral, abdominal subcutaneous, gluteal-femoral subcutaneous and intramuscular adipose tissue, have different metabolic and endocrine degrees, interfering, therefore, with specific form in the process associated with body adiposity in obese and diabetics subjects. The present study seeks to discuss the endocrine and metabolic role of each adipose tissue compartment, by way to assess their contribution to the complications linked to obesity.
TL;DR: A tomato kinase protein and its soybean homolog were found to interact specifically with the nuclear shuttle protein (NSP) of Tomato golden mosaic virus and Tomato crinkle leaf yellows virus through yeast two-hybrid screening and in vitro protein binding assays.
TL;DR: A taxa de aparecimento foliar (TApF) and taxa of along-amento along-filing (TAlF) have been used in this article to evaluate the effect of rebrotacao on folhas vivas perfilho-1.
Abstract: Um experimento foi disposto no delineamento em blocos casualizados, sob o esquema fatorial 3x8, tres dose de N (0, 20 e 40 mg dm-3 semana-1 de N) e oito tempos de rebrotacao (0, 2, 4, 8, 16, 24, 32 e 48 dias apos o corte de uniformizacao), em vasos, em casa-de-vegetacao, com tres repeticoes para cada tratamento, para avaliar as caracteristicas morfogenicas (taxa de aparecimento foliar [TApF] e taxa de alongamento foliar [TAlF]) e estruturais (comprimento medio de folhas [CMF], numero de folhas vivas perfilho-1 [NFVP], peso medio de perfilho [PMP] e densidade de perfilhos [DP]) da Brachiaria brizantha cv. Marandu. A TApF foi afetada significativamente com o aumento da dose de N. Plantas que receberam 40 mg dm-3 semana-1 de N apresentaram filocronos bem inferiores (6,99 dias folhas-1) aos encontrados na testemunha (12,20 dias folhas-1). A TAlF tambem foi bem sensivel a aplicacao de N, elevando-se significativamente com o aumento do suprimento de N, em torno de 185,24 e 264,32%, respectivamente, para as plantas que receberam 20 e 40 mg dm-3 semana-1 de N. O CMF sofreu efeito significativamente positivo com o aumento da dose de N. Tanto a dose de N quanto o tempo de rebrotacao tiveram efeito significativamente positivo sobre o NFVP e o PMP. Apesar do maior NFV, plantas que receberam doses de N tiveram maior perda por senescencia. Os fatores quantitativos estudados tambem tiveram efeito significativamente positivo sobre a DP.
TL;DR: Ethanol extracts from wild plants collected in three different regions of Brazil and from plants cultivated in various soil conditions were tested, and the wild plants were the most active, indicating a good candidate for pre‐clinical tests as a phytotherapeutic agent or for chemical isolation of the active compounds.
Abstract: Bidens pilosa (Asteraceae), a medicinal plant used worldwide, has antimalarial activity as shown in previous work. This study tested ethanol extracts from wild plants collected in three different regions of Brazil and from plants cultivated in various soil conditions. The extracts were active in mice infected with P. berghei: doses of < or =500 mg/kg administered by oral route reduced malaria parasitaemia and mouse mortality; higher doses were found to be less effective. Tested in vitro against three P. falciparum isolates, two chloroquine resistant and one mefloquine resistant, the plants cultivated under standard conditions, and in humus enriched soil, were active; but the wild plants were the most active. Analysis using thin layer chromatography demonstrated the presence of flavonoids (compounds considered responsible for the antimalarial activity) in all plants tested, even though at different profiles. Because B. pilosa is proven to be active against P. falciparum drug-resistant parasites in vitro, and in rodent malaria in vivo, it is a good candidate for pre-clinical tests as a phytotherapeutic agent or for chemical isolation of the active compounds with the aim of finding new antimalarial drugs.
TL;DR: In this paper, the performance of the Century simulation model in an acid tropical soil under different tillage systems including no-tillage (NT) and different plowed systems using Century model was evaluated.
TL;DR: In this paper, a retencao de agua dos horizontes superficiais dos solos estudados foi positivamente correlacionada with os teores de argila e carbono orgânico.
Abstract: Com o intuito de avaliar diferencas de comportamento entre solos das superficies geomorficas Sul-Americana e Velhas da regiao dos Cerrados, todos sob uso atual de cobertura vegetal nativa, foram realizadas caracterizacoes fisicas, quimicas e mineralogicas, bem como feitas analises de componentes principais desses atributos. Com os solos referenciados por sub-regiao e pela superficie geomorfica que representam, tres agrupamentos foram constituidos: Grupo 1: solos de textura argilosa a muito argilosa e hipo a mesoferricos; Grupo 2: solos de textura media a arenosa e hipoferricos; e Grupo 3: solos de textura argilosa a muito argilosa e ferricos. A retencao de agua dos horizontes superficiais dos solos estudados foi positivamente correlacionada com os teores de argila e carbono orgânico. Os solos do Grupo 3 apresentaram a maior oferta de bases trocaveis dos horizontes superficiais, o que foi relacionado, em grande parte, com a maior reciclagem imposta pela formacao florestal local, quando comparada a da formacao de cerrado, presente em 31 dos 33 perfis de solos dos Grupos 1 e 2. O Grupo 3, diferenciado pelos elevados teores de Fe herdados do material de origem, e o grupo mais homogeneo em termos mineralogicos, com todos os perfis hematiticos. Os Grupos 1 e 2 apresentam sobreposicao de composicao mineralogica, sendo o Grupo 1, em termos medios, mais gibbsitico do que o Grupo 2. A maior eficacia do Sistema Brasileiro de Classificacao de Solos, relativamente ao Soil Taxonomy, em discriminar os solos estudados e resultante do uso do carater ferrico concomitantemente a outros atributos comuns aos dois sistemas. A analise de componentes principais auxiliou no entendimento das diferencas e similaridades dos ambientes pedologicos separados no campo.
01 Sep 2004
TL;DR: The authors discute aspectos metodologicos dos estudos de consumo alimentar em criancas e adolescentes, bem como origem historica, importância, vantagens, limitacoes e usos dos metodos empregados for medir a ingestao alimentAR, especialmente em criaças e adolescents, em estudos epidemiologicos populacionais.
Abstract: Este artigo discute aspectos metodologicos dos estudos de consumo alimentar em criancas e adolescentes. Para compreender esses aspectos, descreve, em contexto mais amplo, a importância da Epidemiologia Nutricional no estudo descritivo da relacao da dieta com o surgimento das enfermidades, bem como origem historica, importância, vantagens, limitacoes e usos dos metodos empregados para medir a ingestao alimentar, especialmente em criancas e adolescentes, em estudos epidemiologicos populacionais. Apresenta ainda alguns trabalhos da literatura cientifica classica e contemporânea, demonstrando os resultados obtidos e algumas sugestoes para aperfeicoamento desses metodos. Finalmente, evidencia os aspectos mais relevantes que, por consenso de varios pesquisadores, competem como fatores limitantes ou facilitadores no emprego desses metodos, conferindo a esses, maior validade e reprodutibilidade nos estudos de consumo alimentar de criancas e adolescentes.
TL;DR: Verificou-se que as especies C. spectabilis, S. bicolor, C. ochroleuca, M. aterrima e M. pruriens reduziram significativamente o numero e o peso da materia seca da populacao das plantas daninhas avaliadas nesse aspecto.
Abstract: O presente trabalho foi conduzido na Estacao Experimental da Universidade Federal do Tocantins, Gurupi-TO, Brasil. O experimento foi instalado com o objetivo de avaliar durante 60 dias, em campo, a interferencia de oito especies utilizadas frequentemente como adubos verdes (Mucuna aterrima, Mucuna pruriens, Crotalaria ochroleuca, Crotalaria spectabilis, Canavalia ensiformis, Cajanus cajan, Pennisetum americanum e Sorghum bicolor, hibrido BR304) sobre a comunidade infestante. As especies de plantas daninhas mais frequentes na area do experimento foram: Digitaria horizontalis, Hyptis lophanta e Amaranthus spinosus. Foram realizadas amostragens aos 15, 30, 45 e 60 dias apos a formacao da cobertura, utilizando um quadrado de amostragem equivalente a 0,25 m2. As plantas daninhas foram devidamente identificadas, coletadas, secas e pesadas. O delineamento experimental utilizado foi inteiramente casualizado e constou de nove tratamentos, com quatro repeticoes cada. Verificou-se que as especies C. spectabilis, S. bicolor, C. ochroleuca, M. aterrima e M. pruriens reduziram significativamente o numero e o peso da materia seca da populacao das plantas daninhas avaliadas (D. horizontalis, H. lophanta e A. Spinosus), principalmente as duas ultimas, enquanto P. americanum mostrou-se a menos eficiente nesse aspecto.
TL;DR: A cultivar mais adequada para a producao de sementes sinteticas y os dois reguladores de crescimento nas 5 cultivares, em um estudo comparativo entre os efeitos das duas fontes de explante e osDois regulADores of cresCimento nacionales.
Abstract: Synthetic seeds can be an alternative for those species in which botanical seeds are not viable. One of the major problems of in vitro plant cultivation is the high level of somaclonal variation. The most common factors affecting somaclonal variation are genotype, explant source, in vitro period and cultivation conditions in which the culture is established. In this work, calli were induced using leaf and stem explants of the commercial potato cultivars Achat, Baraka, Baronesa, Bintje, and Contenda in MS culture media supplemented with 1.65 mM of picloram and 11.5 mM of 2,4-D. Seventy and 90 days after induction, DNA samples of 40 calli were compared concerning the effects of the two explant (leaf and stem) and two growth regulator sources on five potatoes cultivars. A total of 20 arbitrary sequence primers were evaluated. The RAPD pattern generated by these primers suggested a high percentage of polymorphic fragments among the five genotypes, indicating a high level of genetic variation among cultivars. Cultivar Baronesa showed the highest number of polymorphic fragments for all treatments. The cultivar Contenda showed the smallest somaclonal variation, for most of the treatments, except for the treatment which consisted of stem explants, picloram (1.65 mM) application, and a 70-day period of callus formation. 'Contenda' is, therefore, the most suitable cultivar for synthetic seed production.
TL;DR: A checklist of the Brazilian Ephemeroptera fauna with all species, genera and families recorded from the country, including the states for which every species is reported, and the pertinent reference is presented.
Abstract: (As especies de Ephemeroptera (Insecta) registradas para o Brasil). Uma lista da fauna de Ephemeroptera do Brasil, com todas as especies, generos e familias registrados para o pais e apresentada, incluindo os estados para os quais as especies estao reportadas assim como a bibliografia pertinente. Comentarios acerca do estado atual do conhecimento da fauna brasileira tambem sao tecidos. Ate o presente momento 10 familias, 63 generos e 166 especies estao registrados. As familias Baetidae e Leptophlebiidae compreendem mais de 50% de todos os registros, enquanto as regioes Norte e Sudeste sao significativamente melhor estudadas que as demais.
TL;DR: The assumption that smaller and more isolated remnants receive fewer ant colonizers and lose more species is tested, which has important implications for conservation strategies because small remnants seem to be more affected by secondary effects of fragmentation, losing more forest species and being invaded more often by generalist species.
Abstract: In this paper we tested the assumption that smaller and more isolated remnants receive fewer ant colonizers and lose more species. We also tested hypotheses to explain such a pattern. We sampled ants in Brazil for 3 years in 18 forest remnants and in 10 grasslands between them. We tested the influence of remnant area and isolation on colonization rate, as well as the effect of remnant area on extinction rate. We tested the correlation between remnant area and isolation to verify the landscape design. Colonization rate was not affected by remnant area or isolation. Extinction rate, however, was smaller in larger remnants. Remnant area and isolation were negatively correlated. We tested two hypotheses related to the decrease in ant species extinction rate with increased remnant area: (i) small remnants support smaller and more extinction-prone populations; and (ii) small remnants are more often invaded by generalist species, which suffer higher extinction inside remnants. The density of ant populations significantly increased with area. Generalist species presented a lower colonization rate in larger remnants, contrary to the pattern observed in forest species. Generalist species suffered more extinction than expected inside remnants. The lack of response of colonization rate to remnant area can be explained by the differential colonization by generalist and forest species. The decrease of ant population density in smaller remnants could be related to loss of habitat quality or quantity. The higher colonization by generalist ant species in the smaller remnants could be related to landscape design, because smaller remnants are more similar to the matrix than larger ones. Our results have important implications for conservation strategies because small remnants seem to be more affected by secondary effects of fragmentation, losing more forest species and being invaded more often by generalist species. Studies that compare only species richness between remnants cannot detect such patterns in species composition.
TL;DR: In this paper, the authors considered the problem of finding a weak positive solution to the mountain pass problem in R2 by combining the Trudinger-Moser inequality and a version of a result due to lions for critical growth.
Abstract: We consider the equation −Δu+V(x)u=f(x,u) for x∈R2 where V:R2→R is a positive potential bounded away from zero, and the nonlinearity f:R2×R→R behaves like exp(α|u|2) as |u|→∞. We also assume that the potential V(x) and the nonlinearity f(x,u) are asymptotically periodic at infinity. We prove the existence of at least one weak positive solution u∈H1(R2) by combining the mountain-pass theorem with Trudinger–Moser inequality and a version of a result due to Lions for critical growth in R2.