Robust ecological pattern formation induced by demographic noise

We demonstrate that demographic noise can induce persistent spatial pattern formation and temporal oscillations in the Levin-Segel predator-prey model for plankton-herbivore population dynamics. Although the model exhibits a Turing instability in mean field theory, demographic noise greatly enlarges the region of parameter space where pattern formation occurs. To distinguish between patterns generated by fluctuations and those present at the mean field level in real ecosystems, we calculate the power spectrum in the noise-driven case and predict the presence of fat tails not present in the mean field case. These results may account for the prevalence of large-scale ecological patterns, beyond that expected from traditional non-stochastic approaches.Comment: Revised version. Supporting simulation at: http://guava.physics.uiuc.edu/~tom/Netlogo

Quelônios aquáticos da Amazônia: um recurso ameaçado

Turtles have long served man as an important food resource in Amazonia. During the colonial period, Portuguese traders disturbed nesting beaches on a large scale in search of eggs which were converted into oil for cooking and lighting. Exploitation was increasingly intense by the end of the 19th century and turtle populations had declined drastically. Although legislation has been passed to protect them, enforcement is lax and turtles face increasing pressure from man not only for food but as a result of habitat disturbance.Os quelônios aquáticos têm servido o homem, há muito tempo, como um importante recurso alimentar. Durante o período colonial, comerciantes portugueses perturbaram praias de desova em grande escala à procura de ovos, os quais eram utilizados como óleo para cozinhar e iluminar. Isto foi aumentando intensamente e, pelo fim do século 19, populações de tartarugas declinaram drasticamente. Apesar de a legislação ter passado a protegê-las, a fiscalização não é suficiente e as tartarugas estão sofrendo crescente pressão do homem, não apenas para comida, mas também pela modificação de seu ambiente

Utilization of game along Brazil's transamazon highway

The hunting methods and game yield from rain forest and second growth along the Transamazon highway are described and the importance of wild meat in the diet of setlers is assessed. The implications of game take with respect to the human carrying capacity of interfluvial forest in Amazonia is also explored.Os métodos de caça e o rendimento na mata e na capoeira, ao longo da Transamazônica, são descritos e a importância de proteína de caça na dieta dos colonos é avaliada. As implicações do rendimento de caça sobre a capacidade da mata de terra firme para suportar populações humanas são também investigadas

Influências culturais e ecológicas na produtividade agrícola ao longo da Transamazônica ()

The paper reviews the government-directed attempt to siphon surplus populations from other regions of Brazil and to settle them along the upland transect of the Transamazon by focusing on problems of agricultural productivity encountered by colonists in a pioneer rain forest environment. Particular attention is paid to cash cropping systems, since one of the objectives of the settlement scheme was to provide opportunities for landless peasants and flagelados to become entrepreneurial farmers. The cultural and ecological problems associated with farming are examined for the period 1970-1975.O trabalho revê a tentativa dirigida pelo INCRA para escoar os excedentes populacionais de outras regiões do Brasil e instalá-los ao longo do trajeto em terra firme da Transamazônica, concentrando-se nos problemas de produtividade agrícola encontrados num meio pioneiro na mata. Particular atenção é conferida a sistemas rentáveis de produção agrícola, uma vez que um dos objetivos do plano de colonização era fornecer oportunidades a lavradores sem terras e flagelados para se tornarem fazendeiros. Os problemas culturais e ecológicos associados com a exploração agrícola são examinados no período 1970-1975

O bico-de-lacre (Estrilda astrild): um passarinho africano na avifauna de Manaus

The African finch Estrilda astrild is the only exotic bird other than the pigeon to have successfully colonized central Amazonia. The species distribution in Brasil is reviewed. E. astrild has gained a foothold in Amazonia by exploiting grasses native to its original home in Africa. The species potential for agricultural damage is small unless it adapts to feeding on rice. It appears unlikely that E. astrild will displace any native birds

A single oral glucose load decreases arterial plasma [K+] during exercise and recovery

AIM: We investigated whether acute carbohydrate ingestion reduced arterial potassium concentration ([K(+)]) during and after intense exercise and delayed fatigue. METHODS: In a randomized, double‐blind crossover design, eight males ingested 300 ml water containing 75 g glucose (CHO) or placebo (CON); rested for 60 min, then performed high‐intensity intermittent cycling (HIIC) at 130% [Formula: see text] , comprising three 45‐s exercise bouts (EB), then a fourth EB until fatigue. Radial arterial (a) and antecubital venous (v) blood was sampled at rest, before, during and after HIIC and analyzed for plasma ions and metabolites, with forearm arteriovenous differences (a‐v diff) calculated to assess inactive forearm muscle effects. RESULTS: Glucose ingestion elevated [glucose](a) and [insulin](a) above CON (p = .001), being, respectively, ~2‐ and ~5‐fold higher during CHO at 60 min after ingestion (p = .001). Plasma [K(+)](a) rose during and declined following each exercise bout in HIIC (p = .001), falling below baseline at 5 min post‐exercise (p = .007). Both [K(+)](a) and [K(+)](v) were lower during CHO (p = .036, p = .001, respectively, treatment main effect). The [K(+)](a‐v diff) across the forearm widened during exercise (p = .001), returned to baseline during recovery, and was greater in CHO than CON during EB1, EB2 (p = .001) and EB3 (p = .005). Time to fatigue did not differ between trials. CONCLUSION: Acute oral glucose ingestion, as used in a glucose tolerance test, induced a small, systemic K(+)‐lowering effect before, during, and after HIIC, that was detectable in both arterial and venous plasma. This likely reflects insulin‐mediated, increased Na(+),K(+)‐ATPase induced K(+) uptake into non‐contracting muscles. However, glucose ingestion did not delay fatigue

Diffusion tensor imaging of Parkinson's disease, multiple system atrophy and progressive supranuclear palsy: a tract-based spatial statistics study

Although often clinically indistinguishable in the early stages, Parkinson's disease (PD), Multiple System Atrophy (MSA) and Progressive Supranuclear Palsy (PSP) have distinct neuropathological changes. The aim of the current study was to identify white matter tract neurodegeneration characteristic of each of the three syndromes. Tract-based spatial statistics (TBSS) was used to perform a whole-brain automated analysis of diffusion tensor imaging (DTI) data to compare differences in fractional anisotropy (FA) and mean diffusivity (MD) between the three clinical groups and healthy control subjects. Further analyses were conducted to assess the relationship between these putative indices of white matter microstructure and clinical measures of disease severity and symptoms. In PSP, relative to controls, changes in DTI indices consistent with white matter tract degeneration were identified in the corpus callosum, corona radiata, corticospinal tract, superior longitudinal fasciculus, anterior thalamic radiation, superior cerebellar peduncle, medial lemniscus, retrolenticular and anterior limb of the internal capsule, cerebral peduncle and external capsule bilaterally, as well as the left posterior limb of the internal capsule and the right posterior thalamic radiation. MSA patients also displayed differences in the body of the corpus callosum corticospinal tract, cerebellar peduncle, medial lemniscus, anterior and superior corona radiata, posterior limb of the internal capsule external capsule and cerebral peduncle bilaterally, as well as the left anterior limb of the internal capsule and the left anterior thalamic radiation. No significant white matter abnormalities were observed in the PD group. Across groups, MD correlated positively with disease severity in all major white matter tracts. These results show widespread changes in white matter tracts in both PSP and MSA patients, even at a mid-point in the disease process, which are not found in patients with PD

Effects of habitat and livestock on nest productivity of the Asian houbara Chlamydotis macqueenii in Bukhara Province, Uzbekistan

To inform population support measures for the unsustainably hunted Asian houbara Chlamydotis macqueenii (IUCN Vulnerable) we examined potential habitat and land-use effects on nest productivity in the Kyzylkum Desert, Uzbekistan. We monitored 177 nests across different semi-arid shrub assemblages (clay-sand and salinity gradients) and a range of livestock densities (0–80 km-2). Nest success (mean 51.4%, 95% CI 42.4–60.4%) was similar across four years; predation caused 85% of those failures for which the cause was known, and only three nests were trampled by livestock. Nesting begins within a few weeks of arrival when food appears scarce, but later nests were more likely to fail owing to the emergence of a key predator, suggesting foraging conditions on wintering and passage sites may be important for nest productivity. Nest success was similar across three shrub assemblages and was unrelated to landscape rugosity, shrub frequency or livestock density, but was greater with taller mean shrub height (range 13–67 cm) within 50 m. Clutch size (mean = 3.2 eggs) and per-egg hatchability in successful nests (87.5%) did not differ with laying date, shrub assemblage or livestock density. We therefore found no evidence that livestock density reduced nest productivity across the range examined, while differing shrub assemblages appeared to offer similar habitat quality. Asian houbara appear well-adapted to a range of semi-desert habitats and tolerate moderate disturbance by pastoralism. No obvious in situ mitigation measures arise from these findings, leaving regulation and control as the key requirement to render hunting sustainable

The conserved C-terminus of the PcrA/UvrD helicase interacts directly with RNA polymerase

Copyright: © 2013 Gwynn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by a Wellcome Trust project grant to MD (Reference: 077368), an ERC starting grant to MD (Acronym: SM-DNA-REPAIR) and a BBSRC project grant to PM, NS and MD (Reference: BB/I003142/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD