350 research outputs found
Ecologia de insetos aquĂĄticos em cĂłrregos do Cerrado: do nicho hutchinsoniano ao distĂșrbio intermediĂĄrio
A regiĂŁo do Cerrado Ă© o segundo maior bioma brasileiro abrangendo cerca de 22% do territĂłrio nacional. Devido a facilidades que o mesmo apresenta para manejo e cultivo do solo, o Cerrado vem sofrendo uma intensa mudança na sua paisagem, aumentando o impacto em todos os seus sistemas naturais. AtravĂ©s de uma coleta sistematizada em 101 cĂłrregos na regiĂŁo da bacia do rio das Almas, centro goiano, pode ser observado como essa mudança na paisagem altera a comunidade de insetos aquĂĄticos bentĂŽnicos. Em um primeiro momento nĂŁo observamos mudanças no nĂșmero de gĂȘneros para diferentes tamanhos de rios. O aumento do impacto, principalmente na regiĂŁo ripĂĄria, leva a uma redução no nĂșmero de gĂȘneros de Ephemeroptera, Plecoptera e Trichoptera. Comunidades em localidades impactadas sĂŁo compostos de subconjuntos das comunidades em locais preservados, apresentando um padrĂŁo de aninhamento. Apesar da redução do nĂșmero de gĂȘneros em locais impactados a riqueza esperada pelo somatĂłrio das probabilidades de ocorrĂȘncia dos gĂȘneros em um determinado valor de integridade se mostra maior tanto em locais conservados como degradados. Assim a taxa de substituição de gĂȘneros tende a ser maior em localidades muito impactadas e bem preservadas. A matriz ambiental no Cerrado Ă© composta em grande parte por ĂĄreas jĂĄ impactadas, o que explicaria essa grande quantidade de gĂȘneros que vivem em locais degradados, atravĂ©s do simples efeito de ĂĄrea. Por Ășltimo comparamos os resultados de dois Ăndices usados para monitoramento ecolĂłgico de cĂłrregos, que visam observar tipos de impactos diferentes no ambiente. NĂŁo houve relação entre o Ăndice de Integridade de Habitat e um Ăndice que mensura teor de poluição na ĂĄgua (BMWPâ), indicando que existe a necessidade do uso dos dois em conjunto para um monitoramento efetivo
Mosquitos (Diptera, Culicidae) habitando tanques foliares de Guzmania brasiliensis Ule (Bromeliaceae) na AmazĂŽnia Central, Brasil
Mosquitoes in the family Culicidae develop their immature forms in different environments depending on various circumstances. This study represents the first contribution to the ecological knowledge of culicids living in the bromeliad G. brasiliensis. The objectives of the study were to compare the Culicidae fauna of bromeliads in two seasonal periods, analyzing their abundance, richness and the influence of pH, conductivity and water volume, on the populations. Sampling was done at Reserva Adolpho Ducke, Manaus, Amazonas, Brazil between 2003 and 2005. Six samplings were done in the rainy season and six in the dry season. On each sampling day, six terrestrial and six epiphytic bromeliads, totaling 144 sampling units, were retrieved. A total of 444 immature mosquitoes were collected, distributed in the following species: Culex (Microculex) stonei Lane & Whitman, Culex (Microculex) chryselatus Dyar & Knab, Culex (Microculex) sp., Wyeomyia (Hystatomyia) autocratica Dyar & Knab and Wyeomyia (Hystatomyia) splendida Bonne-Wepster & Bonne. The relationship between abundance of Culicidae and sampling period was not significant, although abundance was higher in the dry period. There were significant correlations between water volume and the abundance (p = 0.003) and richness (p = 0.001) of culicids. The pH was positively related to the occurrence of the species Wy. autocratica (p= 0.010) and Wy. splendida (p= 0.006), demonstrating the influence of this factor in the structuring of bromeliadinhabiting communities
Niche-Relationships Within and Among Intertidal Reef Fish Species
Niche-related processes (e.g., density or niche-breadth compensation and competition) are fundamental to a broad understanding of community ecology and ecosystem functioning. Most evidences of competition are from controlled indoor trials with few species, and it remains a challenge to estimate competition among multiple species in the field. Here, we analyze stable isotopes and distributional data from 51 fish taxa in six locations in the southwestern Atlantic to predict intraspecific trophic pressure (ITP) and the potential competitive strength among species in a trophic-based framework. We used two proxies built upon 2-dimensional isotopic space (ÎŽ13C vs. ÎŽ15N), its predicted overlap, and fish density to calculate winner and loser taxa in potential paired interspecific competitive interactions. The intraspecific proxy indicated that cryptobenthic fishes are under high among-individual trophic pressure (high densities and small niche sizes). Also, cryptobenthic behavior together with feeding specialization and extremely small-sizes were the most important traits related to low success in interspecific simulations. Although cryptobenthic fishes face strong competitive pressures, there are some known inherent trade-offs to cryptobenthic life such as trophic and habitat use specializations. These seem to compensate and ensure coexistence among cryptobenthic fishes and non-cryptobenthic species. Habitat loss/degradation via urbanization, invasive species and climate-change-driven sea-level rise can reduce the suitability of habitat and increase competition on cryptobenthic species, especially in shallow reefs and intertidal shores
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider
Measurements of multi-particle azimuthal correlations (cumulants) for charged
particles in p-Pb and Pb-Pb collisions are presented. They help address the
question of whether there is evidence for global, flow-like, azimuthal
correlations in the p-Pb system. Comparisons are made to measurements from the
larger Pb-Pb system, where such evidence is established. In particular, the
second harmonic two-particle cumulants are found to decrease with multiplicity,
characteristic of a dominance of few-particle correlations in p-Pb collisions.
However, when a gap is placed to suppress such correlations,
the two-particle cumulants begin to rise at high-multiplicity, indicating the
presence of global azimuthal correlations. The Pb-Pb values are higher than the
p-Pb values at similar multiplicities. In both systems, the second harmonic
four-particle cumulants exhibit a transition from positive to negative values
when the multiplicity increases. The negative values allow for a measurement of
to be made, which is found to be higher in Pb-Pb collisions at
similar multiplicities. The second harmonic six-particle cumulants are also
found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find
which is indicative of a Bessel-Gaussian
function for the distribution. For very high-multiplicity Pb-Pb
collisions, we observe that the four- and six-particle cumulants become
consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and
Pb-Pb are measured. These are found to be similar for overlapping
multiplicities, when a gap is placed.Comment: 25 pages, 11 captioned figures, 3 tables, authors from page 20,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/87
Trichoptera Kirby (Insecta) immature fauna from Rio das Almas Basin and Rio ParanĂŁ, GoiĂĄs State, Brazil, with new records for some genera
K0S and Î production in Pb-Pb collisions at sNNâââââ=2.76ââTeV
The ALICE measurement of K0S and Î production at midrapidity in Pb-Pb collisions at sNNââââ=2.76ââTeV is presented. The transverse momentum (pT) spectra are shown for several collision centrality intervals and in the pT range from 0.4ââGeV/c (0.6ââGeV/c for Î) to 12ââGeV/c. The pT dependence of the Î/K0S ratios exhibits maxima in the vicinity of 3ââGeV/c, and the positions of the maxima shift towards higher pT with increasing collision centrality. The magnitude of these maxima increases by almost a factor of three between most peripheral and most central Pb-Pb collisions. This baryon excess at intermediate pT is not observed in pp interactions at sâ=0.9ââTeV and at sâ=7ââTeV. Qualitatively, the baryon enhancement in heavy-ion collisions is expected from radial flow. However, the measured pT spectra above 2ââGeV/c progressively decouple from hydrodynamical-model calculations. For higher values of pT, models that incorporate the influence of the medium on the fragmentation and hadronization processes describe qualitatively the pT dependence of the Î/K0S ratio
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