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Life history, population dynamics and production of eastern mosquitofish, Gambusia holbrooki (Pisces, Poeciliidae), in rice fields of the lower Mondego River Valley, western Portugal

Cabral, João Alexandre; Marques, João Carlos
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
65.91%
The introduced population of Gambusia holbrooki from the rice fields of the lower Mondego River Valley, Portugal, was studied for 15 months, relating their life cycle and population dynamics with its production, in order to assess the role of the species in the energy flow and secondary production in this type of agro-ecosystem. Two main annual cohorts (1995 and 1996 cohorts) were identified. The females outnumbered males and the average female/male-ratio was 4. The inspection of ovary developmental stages of this viviparous fish, revealed that the most important reproductive period was between April and August. The first recruits were recorded in June and were present thereafter until October. Males from the parental cohort died before August, whereas parental females could survive until October. Mean adjusted fecundity (number of embryos divided by female standard length) peaked in July 1996 (0.95) and in June 1997 (1.05). Females reached greater sizes, had a higher growth rate and lived longer than males. Annual production was estimated at 3.101 g.m-2.year-1 (ash-free dry weight, AFDW), the average biomass at 2.896 g.m-2 (AFDW), and the P/B ratio was 1.071. A conjugation of life history, population dynamics, production and ecological traits (e.g. fast growth...

Canine population dynamics: the potential effect of sterilization campaigns

AMAKU, Marcos; DIAS, Ricardo Augusto; FERREIRA, Fernando
Fonte: PAN AMER HEALTH ORGANIZATION Publicador: PAN AMER HEALTH ORGANIZATION
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
65.92%
Objective. To analyze, through mathematical modeling, the potential ability of sterilization campaigns to reduce the population density of pet dogs. Methods. Mathematical models were constructed to simulate the canine population dynamics and project the results of control strategies based on several sterilization rates. Results. Even at high sterilization rates (for example, 0.80 year(-1)), it would take approximately 5 years to reduce density by 20%. Even so, other sources of population growth, such as the importing of dogs from other geographic areas, could outweigh the effects of a sterilization program. Conclusions. A program`s effectiveness is contingent upon not only on the sterilization rate, but also the rate of population growth. Sterilization campaigns may potentially reduce population density, but this reduction may not be immediately evident.

Population dynamics of genetically diverse Plasmodium falciparum lineages: community-based prospective study in rural Amazonia

ORJUELA-SANCHEZ, P.; SILVA-NUNES, M. Da; SILVA, N. S. Da; SCOPEL, K. K. G.; GONCALVES, R. M.; MALAFRONTE, R. S.; FERREIRA, M. U.
Fonte: CAMBRIDGE UNIV PRESS Publicador: CAMBRIDGE UNIV PRESS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.93%
Temporal changes in the prevalence of antigenic variants in Plasmodium falciparum populations have been interpreted as evidence of immune-mediated frequency-dependent selection, but evolutively neutral processes may generate similar patterns of serotype replacement. Over 4 years, we investigated the population dynamics of P. falciparum polymorphisms the community level by using 11 putatively neutral microsatellite markers. Plasmodium falciparum Populations were less diverse than sympatric P. vivax isolates, with less multiple-clone infections, lower number of alleles per locus and lower Virtual heterozygosity, but both species showed significant multilocus linkage disequilibrium. Evolutively neutral P. falciparum polymorphisms showed a high turnover rate, with few lineages persisting for several months in the population. Similar results had previously been obtained, in the same community, for sympatric P. vivax isolates. In contrast, the prevalence of the 2 dimorphic types of a major antigen, MSP-2, remained remarkably stable throughout the Study period. We Suggest that the relatively fast turnover of parasite lineages represents the typical population dynamics of neutral polymorphisms in small populations, with clear implications for the detection of frequency-dependent selection of polymorphisms.; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico(CNPq)[470570/2006-7]; Fundacao de Amparo A Pesquisa do Estado de Sao Paulo (FAPESP)[07/51199-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); National Institutes of Health of USA (NIH)[RO1 AI 075416-01]; U.S. National Institutes of Health (NIH)

Dinâmica populacional de afídeos (Hemiptera: Aphididae) em árvores cítricas no município de Nova Granada - SP; Population dynamics of aphids (Hemiptera: Aphididae) on citrus trees in Nova Granada County, São Paulo State, Brazil

Primiano, Eduardo Luiz Vescove
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/10/2005 PT
Relevância na Pesquisa
65.97%
O possível envolvimento de afídeos na transmissão de vírus associados à morte súbita dos citros (MSC) indica a necessidade de monitoramento desses insetos para melhor compreender sua dinâmica populacional e a epidemiologia da doença. Esta pesquisa teve como principal objetivo a determinação das principais espécies de afídeos que colonizam pomares de laranja doce [Citrus sinensis (L.) Osbeck] de um município afetado pela MSC, no Norte do Estado de São Paulo, bem como o estudo da dinâmica populacional destes insetos. Preliminarmente, padronizou-se uma metodologia de amostragem de afídeos, baseando-se em uma análise da distribuição espacial destes insetos na copa de árvores cítricas, em dois pomares de laranja doce, localizados em Comendador Gomes-MG e Santa Cruz do Rio Pardo-SP. Em cada pomar, delimitou-se um talhão com 960 plantas numeradas, no qual 100 plantas foram selecionadas ao acaso, para as avaliações. Cada árvore foi dividida em três estratos: i) inferior (0 – 1,0 m); ii) médio (1,0 – 1,8 m); e iii) superior (>1,8 m). Os estratos foram divididos em quadrantes (Leste, Oeste, Norte e Sul), amostrando-se uma brotação por quadrante, totalizando 12 brotações por planta. Através de análise de variância...

Dinâmica populacional de Diaphorina citri Kuwayama (Hemiptera: Liviidae) em pomares cítricos do Estado de São Paulo; Population dynamics of Diaphorina citri Kuwayama (Hemiptera: Liviidae) in citrus orchards of Sao Paulo State, Brazil

Sales, Tiago de Melo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/05/2015 PT
Relevância na Pesquisa
65.92%
O Huanglongbing (HLB) é a doença dos citros mais importante em todo mundo, por afetar todas as variedades cítricas cultivadas e ser de difícil controle. No Brasil, onde afeta as principais regiões produtoras de citros, a doença vem se espalhando e causando enormes prejuízos à atividade. O manejo do HLB depende da utilização de ações integradas, dentre elas o controle do inseto vetor, o psilídeo-asiátco-dos-citros, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Para controlar de forma eficiente esse inseto vetor é necessário que se conheça, por meio de amostragens eficazes, suas características de dinâmica tanto temporal quanto espacial, identificando regiões mais propensas à infestações e épocas do ano em que o inseto se desenvolve melhor. Por isso, o presente estudo teve como objetivos: a) avaliar a dinâmica temporal do psilídeo D. citri em pomares do Estado de São Paulo, examinando o efeito de diferentes regiões, épocas do ano e idade dos plantios; b) verificar a existência de diferenças no número de insetos amostrados em diferentes alturas da planta cítrica, comparando diferentes métodos de amostragem; e c) investigar o padrão de distribuição espacial do inseto em pomares de diferentes idades. Para isso foram realizados levantamentos ao longo de dois anos em seis localidades...

Population dynamics of Musca domestica (Diptera: Muscidae): experimental and theoretical studies at different temperatures

Tardelli, Carina Aparecida; Godoy, Wesley Augusto Conde; Mancera, Paulo Fernando Arruda
Fonte: Brazilian Archives of Biology and Technology Publicador: Brazilian Archives of Biology and Technology
Tipo: Artigo de Revista Científica Formato: 775-783
ENG
Relevância na Pesquisa
65.96%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Neste estudo a dinâmica populacional de M. domestica foi avaliada em duas temperaturas, 20ºe 30ºC. A dinâmica foi modelada utilizando um modelo de crescimento populacional dependente da densidade. As temperaturas investigadas no estudo não produziram mudança qualitativa em termos de comportamento dinâmico, ou seja, a dinâmica populacional de M. domestica foi caracterizada por um equilíbrio estável em ambas as temperaturas. Entretanto, o ponto de equilíbrio foi influenciado pelos resultados obtidos nas diferentes temperaturas. A diferença entre os autovalores obtidos nas duas temperaturas foi a provável causa da diferença entre os pontos de equilíbrio. As implicações destes resultados para a dinâmica populacional de M. domestica são discutidas.; In the present study, the population dynamics of M. domestica was evaluated at two different temperatures, 20 and 30ºC. The dynamics was modeled using a density-dependent model of population growth. The temperatures investigated in this study produced no qualitative change in terms of dynamic behaviour, i. e. the population dynamics of M. domestica was characterized by a stable equilibrium at both temperatures. However...

Population dynamics of Chrysomya megacephala (Diptera : Calliphoridae) at different temperatures

Silva, ICR; Godoy, WAC; Von Zuben, C. J.; Mancera, PFA
Fonte: Entomological Soc Southern Africa Publicador: Entomological Soc Southern Africa
Tipo: Artigo de Revista Científica Formato: 157-163
ENG
Relevância na Pesquisa
65.89%
In this study we analysed the theoretical population dynamics of C. megacephala, an exotic blowfly, kept at 25 and 30degreesC, using a density-dependent mathematical model, with parametric estimates of survival and fecundity in the laboratory. No change in terms of oscillation patterns was found for the two temperatures. The populations exhibited a two-point limit cycle, i.e. oscillations between two fixed points, at 25 and 30degreesC. However a quantitative change was observed, indicating that at 25degreesC the number of immatures in equilibrium is 1176 and at 30degreesC, 1944. The implications of this difference in terms of equilibrium for population dynamics of C. megacephala are discussed.

Population dynamics of the seabob shrimp Xiphopenaeus kroyeri (Dendrobranchiata, Penaeidae) in south-eastern Brazil

Heckler, G.; Simões, S.; Santos, APF; Fransozo, A.; Costa, R.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 17-24
ENG
Relevância na Pesquisa
65.92%
The population dynamics, including the sex ratio, reproductive period, individual growth and longevity, and population structure of the shrimp Xiphopenaeus kroyeri, are described. The shrimps were collected monthly from July 2005 to June 2007 at four sites in Ubatuba Bay, Brazil. The salinity, temperature, depth, organic matter content and sediment grain size were measured at each site. Specimens were quantified and sexed, their carapace length measured and their gonads were classified according to the stage of maturation. A von Bertalanffy model was used to estimate the individual growth, and longevity was calculated using its inverted formula. In total, 6 470 individuals were examined and the number of males and females differed significantly in favour of females. During some periods, the segregation could be related to the reproductive period. Reproductive females were captured throughout the sampled period, and there were biannual peaks that were followed by peaks of juveniles. Carapace growth was less for males than for females, which is likely related to oocyte production and the higher fecundity of the females. The higher probability of female capture can be related to their longer foraging to sustain the enhanced food requirement during the ovarian maturation period. © 2013 Copyright NISC (Pty) Ltd.

Dinâmica populacional de aves de rapina e suas presas em áreas abertas de Cerrado; Population dynamics of birds of prey and their prey in open areas of Cerrado

Leandro Claudio Baumgarten
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 27/11/2007 PT
Relevância na Pesquisa
65.95%
Aves de rapina são pouco estudadas no Brasil e existem poucas informações sobre os padrões de dinâmica populacional das espécies que ocorrem no país, assim como os fatores que os influenciam. Com o objetivo de caracterizar a dinâmica populacional de rapineiros e como ela é influenciada pela abundância de presas, foi realizado um acompanhamento de 36 meses das populações de aves de rapina e pequenos mamíferos no Parque Nacional das Emas (Mineiros-GO). Além disto, foram coletadas informações sobre os padrões de atividade das presas para caracterizar mais claramente sua disponibilidade para predadores. A amostragem das presas foi realizada em nove estações de captura, cada uma com 24 armadilhas "pitfall" e a abundância de rapineiros foi a avaliada por censo de carro. Foram realizadas 12 coletas de dados com intervalos de dois meses entre si. Não foi verificada variação de abundância em nenhuma das espécies de aves de rapina entre anos, ao longo do estudo, no entanto a maioria delas apresentou grandes flutuações sazonais. Os dados obtidos sugerem que estas variações foram causadas principalmente pela movimentação das aves para dentro e fora da reserva. Para os pequenos mamíferos não foi encontrada variação sazonal significativa...

Life history, population dynamics and production of eastern mosquitofish, Gambusia holbrooki (Pisces, Poeciliidae), in rice fields of the Lower Mondego River Valley, West Portugal.

Cabral, João Alexandre; Marques, João Carlos
Fonte: Universidade de Trás-os-Montes e Alto Douro Publicador: Universidade de Trás-os-Montes e Alto Douro
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.91%
The introduced population of Gambusia holbrooki from the rice fields of the lower Mondego River Valley, Portugal, was studied for 15 months, relating their life cycle and population dynamics with its production, in order to assess the role of the species in the energy flow and secondary production in this type of agro-ecosystem. Two main annual cohorts (1995 and 1996 cohorts) were identified. The females outnumbered males and the average female/male-ratio was 4. The inspection of ovary developmental stages of this viviparous fish, revealed that the most important reproductive period was between April and August. The first recruits were recorded in June and were present thereafter until October. Males from the parental cohort died before August, whereas parental females could survive until October. Mean adjusted fecundity (number of embryos divided by female standard length) peaked in July 1996 (0.95) and in June 1997 (1.05). Females reached greater sizes, had a higher growth rate and lived longer than males. Annual production was estimated at 3.101 g×m–2×year–1 (ash-free dry weight, AFDW), the average biomass at 2.896 g×m–2 (AFDW), and the P/B ratio was 1.071. A conjugation of life history, population dynamics, production and ecological traits (e.g. fast growth...

Population Dynamics Modeling of Arapaima gigas

Coutinho,Eliane dos Santos de Souza; Bevilacqua,Luiz; Queiroz,Helder Lima de
Fonte: Instituto Nacional de Pesquisas da Amazônia Publicador: Instituto Nacional de Pesquisas da Amazônia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
Relevância na Pesquisa
65.9%
Pirarucu (Arapaima gigas) has been of the most important natural fishing resources of the Amazon region. Due to its economic importance, and the necessity to preserve the species hand, field research concerning the habits and behavior of the pirarucu has been increasing for the last 20 years. The aim of this paper is to present a mathematical model for the pirarucu population dynamics considering the species peculiarities, particularly the male parental care over the offspring. The solution of the dynamical systems indicates three possible equilibrium points for the population. The first corresponds to extinction; the third corresponds to a stable population close to the environmental carrying capacity. The second corresponds to an unstable equilibrium located between extinction and full use of the carrying capacity. It is shown that lack of males’ parental care closes the gap between the point corresponding to the unstable equilibrium and the point of stable non-trivial equilibrium. If guarding failure reaches a critical point the two points coincide and the population tends irreversibly to extinction. If some event tends to destabilize the population equilibrium, as for instance inadequate parental care, the model responds in such a way as to restore the trajectory towards the stable equilibrium point avoiding the route to extinction. The parameters introduced to solve the system of equations are partially derived from limited but reliable field data collected at the Mamirauá Sustainable Development Reserve (MSDR) in the Brazilian Amazonian Region.

Population dynamics of Musca domestica (Diptera: Muscidae): experimental and theoretical studies at different temperatures

Tardelli,Carina Aparecida; Godoy,Wesley Augusto Conde; Mancera,Paulo Fernando Arruda
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2004 EN
Relevância na Pesquisa
65.96%
In the present study, the population dynamics of M. domestica was evaluated at two different temperatures, 20 and 30ºC. The dynamics was modeled using a density-dependent model of population growth. The temperatures investigated in this study produced no qualitative change in terms of dynamic behaviour, i. e. the population dynamics of M. domestica was characterized by a stable equilibrium at both temperatures. However, the steady state was influenced by the results obtained at different temperatures. The difference between the eigenvalues obtained at the two temperatures was probably the cause of the difference between the distinct steady states. The implications of these results for the population dynamics of M. domestica are discussed.

Planting Date and Soybean Cultivar Maturity Group Affect Population Dynamics of Heterodera glycines, and All Affect Yield of Soybean

Riggs, R. D.; Wrather, J. A.; Mauromoustakos, A.; Rakes, L.
Fonte: Society of Nematologists Publicador: Society of Nematologists
Tipo: Artigo de Revista Científica
Publicado em /12/2000 EN
Relevância na Pesquisa
65.91%
Five soybean cultivars, one each from Maturity Groups (MG) III, IV, V, VI, and VII, all susceptible to Heterodera glycines, were planted in H. glycines-infested soil in April, May, June, and July at multiple locations in Arkansas and Missouri. The purpose of the study was to determine whether planting early reduces yield losses due to H. glycines. The population levels of cysts, eggs, and secondstage juveniles of H. glycines were determined from soil samples collected at planting and harvest. Yields were measured from the two middle rows of 4.9 or 6.1-m four-row plots. The population dynamics of the nematode varied with planting date, cultivar, MG, and initial nematode population. Generally, the lowest reproductive factor (Rf = final population/initial population) for any year was on the MG III cultivar, regardless of planting date or field location. Also, the Rf was generally lower on each cultivar planted in April than in June or July. The highest Rf values were on cultivars in MG VI or VII planted in June or July. Yields were not consistently correlated with initial nematode population level. Early planting of late-maturing soybean cultivars may be profitable, but early planting of MG III cultivars, though supporting little if any increase in nematode numbers...

Population dynamics of different genotypes of Daphnia pulicaria under varying food qualities

Pham, Joanne
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN
Relevância na Pesquisa
65.91%
Stoichiometric food quality, or the carbon to phosphorus (C:P) ratio, is known to be influential on life history of aquatic organisms. Daphnia are heavily impacted by the C:P ratio of the environment that they live in, since they have high requirements for phosphorus compared to other crustaceous zooplankton. Previous studies have shown that individuals fed limited-phosphorus algae exhibited decreases in several life history traits, such as clutch size and age of maturity. Although the effects of stoichiometry on life history are fairly well known, the resulting population dynamics are not. Nine genotypes of Daphnia pulicaria were studied under two food qualities—a C:P ratio of 200 and 600 (the lower the ratio, the better quality the food). The number of individuals and size class data, which corresponds to a specific size (i.e. juvenile or adult), were collected. From there, mean population density, initial growth until peak abundance, and the ratio of juveniles to adults were calculated and analyzed, along with food treatment comparisons. The calculated values are called data probes, which summarize time series data into a single data point in order for analysis. Although no significant differences were found for any probe, variation was still present among genotypes and treatments. However...

Climate change impacts population dynamics and distribution shift of moose (Alces alces) in Heilongjiang Province of China

Dou, H.; Jiang, G.; Stott, P.; Piao, R.
Fonte: Blackwell Science Asia Publicador: Blackwell Science Asia
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
65.97%
The earth is experiencing obvious climate warming, which may impact population dynamics and the distribution of moose (Alces alces). In this study, we examined the effects of density dependence, temperature, snow depth, and the vegetation (NDVI) on the population dynamics of moose in Heilongjiang Province of China using historical data. Our results demonstrated that moose distribution had continued to contract from the 1980s to the 1990s; moose densities and late spring temperatures in the 1980s were negatively correlated to the rate of increase of the moose population; low and high snow depths in the 1990s showed positive and negative effects, respectively, on the rate of population increase; and the effect of NDVI in the 1980s was similar to the effect of snow depth. Therefore, we confirmed that moose population dynamics is influenced both by intrinsic density-dependent and extrinsic habitat factors, especially late spring temperatures. In addition, an increase in late spring temperatures may shift the southern limit of the distribution of the moose northwards, or may isolate the southernmost portion of the moose population because the rate of warming is higher to the north of a present latitudinal constriction in range than it is at the latitude of the southernmost moose.; Hongliang Dou...

Mercury bioaccumulation and the population dynamics of Mesopodopsis slabberi (Crustacea: Mysidacea) along a mercury contamination gradient

D'Ambrosio, M.; Marques, S. C.; Azeiteiro, U. M.; Pardal, M. A.; Pereira, E.; Duarte, A. C.; Cardoso, P. G.
Fonte: Springer Science Publicador: Springer Science
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.91%
The mercury bioaccumulation and population dynamics of the mysid Mesopodopsis slabberi was assessed along a mercury gradient in Ria de Aveiro (Portugal). M. slabberi is one of the most important mysid species in European temperate coastal shallow waters playing a key ecological role. Nevertheless, no references were found concerning the possible consequences of the Hg on the trophodynamics of these coastal ecosystems. M. slabberi showed a clear bioaccumulation along the Hg gradient and through life, with mature females reaching the highest concentrations. In terms of population structure, higher densities and biomasses of M. slabberi were assessed in the most contaminated areas contrarily to the least polluted areas. Despite the mercury accumulation in its tissues no strong negative effects on the structure and population dynamics of the species were observed. However, mysids might be important in the transfer of metals from the sediments and zooplankton to higher trophic levels such as fishes, most of them with commercial interest.; This work was supported by FCT (Fundac¸a˜o para a Cieˆncia e Tecnologia) through a project n. FCOMP-01-0124- FEDER-010598 (MERCOAST, Refa. FCT PTDC/MAR/101906/ 2008) and by POPH and QREN—Promotion of scientific job funded by European social fund and national funds of MEC.

Ecology of the polychaete Nereis diversicolor in the Canal de Mira (Ria de Aveiro, Portugal): Population dynamics, production and oogenic cycle

Abrantes, A.; Pinto, F.; Moreira, M. H.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.91%
The population of Nereis diversicolor O.F. Müller was studied in 1993 and 1994 at three intertidal areas along the estuarine gradient in the Canal de Mira (Ria de Aveiro). The population dynamics, secondary production and growth were followed for the 2-year period, whereas in the second year, a study on the oogenic cycle was also carried out. For the population dynamics and production studies, core samples were collected monthly at each site, and for the study of the oogenic cycle, medium size and large individuals were sampled from the sediment. Mean annual densities were higher (573–718 ind.m–2) at a station located in the middle zone of the channel, followed by the outer (190–275 ind.m–2) and the innermost (43–94 ind.m–2) stations. A cohort analysis by `Bhatta' software enabled the separation of the cohorts present at each date, and two cohorts were followed from recruitment to extinction. The secondary production ranged from 15.9 to 74.2 g ash free dry weight.m–2.year–1 and the View the MathML sourceratio from 4.4 to 7.9. The average body growth rate varied between 0.16 and 0.20 mm.d–1 for worms longer than 2 cm. Two recruitment seasons were detected each year. Two spawning periods were also observed, one in the spring and the other in early autumn.

Population Dynamics of Heterodera glycines in Conventional Tillage and No-Tillage Soybean/Corn Cropping Systems

Noel, G. R.; Wax, L. M.
Fonte: Society of Nematologists Publicador: Society of Nematologists
Tipo: Artigo de Revista Científica
Publicado em /03/2003 EN
Relevância na Pesquisa
65.91%
The effects of no-tillage (NT), conventional tillage (CT), and crop rotation on soybean yield and population dynamics of Heterodera glycines were compared during a 7-year study in a silty clay loam soil with 6% organic matter. Either H. glycines-resistant 'Linford' soybean or susceptible 'Williams 82' soybean was rotated with corn and grown on 76-cm-wide rows in both tillage systems. Soybean was planted in 1994, 1996, 1998, 1999, and 2000. Yield of Linford was significantly greater than Williams 82 in all years. Soybean yield was affected by tillage in 1999 and 2000. No-tillage production tended to support more reproduction (R = number of eggs at harvest/number of eggs at planting) on both cultivars. The largest R for Williams 82 were in 1998: 58.35 for NT plots and 11.78 for CT plots. For Linford, the largest R were 12.09 for NT plots in 1996, and 3.71 for CT in 1999. When corn was planted, R decreased more in NT. When soybean was planted in years subsequent to 1994, numbers of eggs at harvest (Pf) were greater for Williams 82 NT than for Williams 82 CT or Linford in both tillage systems; however, crop rotation with corn negated these population increases. The soil became suppressive to H. glycines in 1999 and was suppressive in 2000. After the 3 years of continuous soybean...

Life History and population dynamics of the marine cladoceran Penilia avirostris (Branchiopoda: Cladocera) in the Catalan Sea (NW Mediterranean)

Atienza, Dacha; Saiz, Enric; Skovgaard, Alf; Trepat, Isabel; Calbet, Albert
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
Relevância na Pesquisa
65.89%
13 pages, 9 figures, 2 figures Full text version available Open Acces at: http://www.icm.csic.es/bio/projects/icmicrobis/pdf; Penilia avirostris is a cosmopolitan marine cladoceran that inhabits coastal and shelf waters of most low and mid latitude ecosystems. In this study we describe the life history and population dynamics of P. avirostris at a fixed coastal station in the NW Mediterranean Sea. This marine cladoceran was very seasonal, having population maxima in summer (2500-3000 ind m–3), and being practically absent from the water column for the rest of the year. The population typically collapsed in late summer – early autumn, and this decline was accompanied by a shift to gametogenetic reproduction, allowing the production of resting eggs to ensure the continuity of the species in the following season. Estimated birth rates of P. avirostris in the Catalan Sea ranged between 0.097 and 0.46 d–1 and seemed to be decoupled from changes in P. avirostris standing stocks. Birth rates were mainly dependent on the changes in abundance of embryo-carrying females and their brood size, because during the period of population plateau the temperature-dependent embryonic developmental time was rather similar (2.3 to 2.7 days). Neonates are like miniature adults and need a very short period of growth and moulting to reach the reproductive stage. This life-history trait can explain the fast blooming and dominance of plankton communities by P. avirostris under suitable conditions. Finally...

Impact of simian immunodeficiency virus infection on chimpanzee population dynamics.;

Rudicell, RS; Holland Jones, J; Wroblewski, EE; Learn, GH; Li, Y; Robertson, JD; Greengrass, E; Grossmann, F; Kamenya, S; Pintea, L; Mjungu, DC; Lonsdorf, EV; Mosser, A; Lehman, C; Collins, DA; Keele, BF; Goodall, J; Hahn, BH; Pusey, AE; Wilson, ML
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Artigo de Revista Científica Formato: e1001116 - ?
Publicado em //2010 ENG; EN_US
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Like human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus of chimpanzees (SIVcpz) can cause CD4+ T cell loss and premature death. Here, we used molecular surveillance tools and mathematical modeling to estimate the impact of SIVcpz infection on chimpanzee population dynamics. Habituated (Mitumba and Kasekela) and non-habituated (Kalande) chimpanzees were studied in Gombe National Park, Tanzania. Ape population sizes were determined from demographic records (Mitumba and Kasekela) or individual sightings and genotyping (Kalande), while SIVcpz prevalence rates were monitored using non-invasive methods. Between 2002-2009, the Mitumba and Kasekela communities experienced mean annual growth rates of 1.9% and 2.4%, respectively, while Kalande chimpanzees suffered a significant decline, with a mean growth rate of -6.5% to -7.4%, depending on population estimates. A rapid decline in Kalande was first noted in the 1990s and originally attributed to poaching and reduced food sources. However, between 2002-2009, we found a mean SIVcpz prevalence in Kalande of 46.1%, which was almost four times higher than the prevalence in Mitumba (12.7%) and Kasekela (12.1%). To explore whether SIVcpz contributed to the Kalande decline, we used empirically determined SIVcpz transmission probabilities as well as chimpanzee mortality...