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The regeneration niche defines the specific environmental requirements of the early phases of a plant's life cycle. It is critical for the long-term persistence of plant populations, particularly for obligate seeders that are highly vulnerable to stochastic events in fire-prone ecosystems. Here, we assessed germination characteristics and the relationship between population structure, soil seed bank density and fire response in Stachystemon vinosus (Euphorbiaceae), a rare endemic shrub from Western Australia, from burnt and long unburnt habitats. Many plants in long unburnt habitat were similar in size to those in recently burnt habitat. Soil seed bank density was related to plant abundance and fire history with density lower in burnt than unburnt sites. Thus, inter-fire recruitment may play a critical role in the requirements of the study species. To assess the dormancy status and germination requirements we used a ‘move-along’ experiment with temperatures from six seasonal phases of the year. Seeds were incubated under light and dark conditions, with and without smoked water, and with and without dry after-ripening. Germination was most effective when seeds were treated with smoked water and incubated in the dark at temperatures resembling autumn/winter conditions. After-ripening increased germination in light and dark incubated seeds in the absence of smoked water but was unnecessary for optimal germination in smoked water treated seeds. Irrespective of treatment, seeds showed a requirement for cooler temperatures for germination. These results suggest that rising temperatures and changes in fire regime associated with global warming may alter future germination responses of Stachystemon vinosus.
Harvest weed seed control (HWSC) techniques have been implemented in Australian cropping systems to target and reduce the number of weed seeds entering the seedbank and thereby reduce the number of problematic weeds emerging in subsequent years to infest subsequent crops. However, the influence of HWSC on ameliorating herbicide-resistance (HR) evolution has not been investigated. This research used integrated spatial modeling to examine how the frequency and efficacy of HWSC affected the evolution of resistance to initially effective herbicides. Herbicides were, in all cases, better protected from future resistance evolution when their use was combined with annual HWSC. Outbreaks of multiple HR were very unlikely to occur and were nearly always eliminated by adding annual, efficient HWSC. The efficacy of the HWSC was important, with greater reductions in the number of resistance genes achieved with higher-efficacy HWSC. Annual HWSC was necessary to protect sequences of lower-efficacy herbicides, but HWSC could still protect herbicides if it was used less often than once per year, when the HWSC and the herbicides were highly effective. Our results highlight the potential benefits of combining HWSC with effective herbicides for controlling weed populations and reducing the future evolution of HR.
Impacted third molars (I3Ms) are blocked from fully erupting; many I3Ms are asymptomatic, however there could be pain and pathological changes. Historically, I3Ms were removed prophylactically. Current options in the United Kingdom include either retention with standard care (watchful waiting), or removal due to pathological changes. We conducted a systematic review of the prophylactic removal of asymptomatic impacted mandibular third molars (IM3Ms) compared with standard care.
We searched five electronic databases from 1999 onwards. Inclusion criteria: randomized and non-randomized trials, observational studies, and systematic reviews (SRs) comparing the prophylactic removal of IM3Ms with standard care or studies assessing the outcomes of either approach; outcomes included pathology associated with retention, postoperative complications, adverse effects of treatment and health-related quality of life. Two reviewers independently screened all titles and/or abstracts, applied inclusion criteria to potentially relevant publications, and quality assessed and data extracted the included studies. No meta-analysis or network meta-analyses were undertaken.
Following screening of 11,373 references, 13 studies (four cohort studies and nine SRs) were included. One cohort study investigated the prophylactic removal of asymptomatic IM3Ms in comparison with standard care and retention, two investigated the prophylactic removal of asymptomatic IM3Ms, and one studied the retention and standard care of asymptomatic IM3Ms. Two studies reporting surgical complications found no serious complications; however, one study reported intense pain and postoperative infection. Pathological changes due to retention of asymptomatic IM3Ms were reported by three studies. Nine SRs of the management of third molars were included in this review, however none focused solely on IM3Ms.
Consistent with previous systematic reviews, we found no RCT data to support or refute the prophylactic removal of asymptomatic IM3Ms, despite extensive searching of the literature. The review however did identify evidence from two longitudinal studies demonstrating the outcomes when asymptomatic IM3Ms are left in situ.
Maternal stress during pregnancy has pervasive effects on stress responsivity in children. This study is the first to test the hypothesis that maternal prenatal depression, as observed in South India, may be associated with how foetuses respond to a potentially stressful stimulus. We employed measures of foetal heart rate at baseline, during exposure to a vibroacoustic stimulus, and post-stimulation, to study patterns of response and recovery in 133 third trimester foetuses of depressed and non-depressed mothers. We show that the association between maternal depression and foetal stress responsivity is U-shaped with foetuses of mothers with high and low depression scores demonstrating elevated responses, and poorer recovery, than foetuses of mothers with moderate levels. The right amount of intra-uterine stimulation is important in conditioning foetuses towards optimal regulation of their stress response. Our results imply that, in certain environmental contexts, exposure to moderate amounts of intra-uterine stress may facilitate this process.
As climates change, some plant species will need to migrate across landscapes fragmented by unsuitable environments and human activities to colonize new areas with suitable climates as previously habited areas become uninhabitable. Previous modelling of plant's migration potential has generally assumed that climate changes at a constant rate, but this ignores many potentially important aspects of real climate variability. In this study, a spatially explicit simulation model was used to investigate how interannual climate variability, the occurrence of extreme events and step changes in climate might interact with gradual long-term climate change to affect plant species’ capacity to migrate across fragmented landscapes and persist. The considered types of climate variability generally exacerbated the negative effects of long-term climate change, with a few poignant exceptions where persistence of long-lived trees improved. Strategic habitat restoration ameliorated negative effects of climate variability. Plant functional characteristics strongly influenced most results. Any modelling of how climate change may affect species persistence, and how actions such as restoration may help species adapt, should account for both short-term climate variability and long-term change.
A wild population of a plant species, especially a cross-pollinated species,
can display considerable genetic variation. Genetic variability is evident
in differential susceptibility to an herbicide because the population can
show continuous phenotypic variation. Recent, recurrent selection studies
have revealed that phenotypic variation in response to low herbicide rates
is heritable and can result in rapid evolution of herbicide resistance in
genetically variable cross-pollinated rigid ryegrass. In this study, the
heritable genetic variation in an herbicide-susceptible rigid ryegrass
population was exploited to shift the population toward greater herbicide
susceptibility by recurrent selection. To enhance herbicide susceptibility,
herbicide-susceptible rigid ryegrass plants were divided into two identical
clones, and one series of cloned plants was treated with a low rate of
herbicide (diclofop). The nontreated clones of individuals that did not
survive the herbicide treatment were selected and bulk-crossed to obtain the
susceptible progeny. After two cycles of selection, the overall
susceptibility to diclofop was doubled. The results indicate that minor
genes for resistance are present in an herbicide-susceptible rigid ryegrass
population, and their exclusion can increase susceptibility to diclofop.
The present paper compares standard and novel methods for analysing aggregated patterns of plant death in designed field experiments; these methods include binomial (BN), beta-binomial (BBN), logistic-normal-binomial (LNB), BN models with random blocks, BN models with smooth-scale spatial components and principal coordinates of neighbour matrices (PCNM). PCNM is a relatively new technique used in ecology to determine how much observed variability can be explained by spatial and environmental variables, and has not yet been applied to agricultural studies. The survival data of two pasture species, collected from a designed field experiment that was replicated at multiple locations, were used. First, the occurrence of overdispersion was tested using the BN and BBN distributions. Goodness-of-fit tests proved that the BBN model provided a better description (better fit) of the observed data in some cases than did the BN distribution, indicating overdispersion was present. When overdispersion was not present, the BN distribution was adequate to describe the data, and the use of the BBN distribution was superfluous. It is then shown that the PCNM approach, the BN model with smooth-scale spatial components and the LNB model were able to account for some of the variation as spatial variability, thus reducing the species effect compared with that explained under the standard BN model. The amount of variation among species according to the BN model and the BN model with random blocks was similar. Therefore, it is argued that the novel PCNM approach warrants further testing when exploring the spatial variability in designed experiments in agriculture and using LNB, PCNM and BN with smooth-scale spatial components may provide better predictions of species effects than do other, more conventional, approaches.
Herbicide rate cutting is an example of poor use of agrochemicals that can have potential adverse implications due to rapid herbicide resistance evolution. Recent laboratory-level studies have revealed that herbicides at lower-than-recommended rates can result in rapid herbicide resistance evolution in rigid ryegrass populations. However, crop-field-level studies have until now been lacking. In this study, we examined the impact of low rates of diclofop on the evolution of herbicide resistance in a herbicide-susceptible rigid ryegrass population grown either in a field wheat crop or in potted plants maintained in the field. Subsequent dose–response profiles indicated rapid evolution of diclofop resistance in the selected rigid ryegrass lines from both the crop-field and field pot studies. In addition, there was moderate level of resistance in the selected lines against other tested herbicides to which the population has never been exposed. This resistance evolution was possible because low rates of diclofop allowed substantial rigid ryegrass survivors due to the potential in this cross-pollinated species to accumulate all minor herbicide resistance traits present in the population. The practical lesson from this research is that herbicides should be used at the recommended rates that ensure high weed mortality to minimize the likelihood of minor herbicide resistance traits leading to rapid herbicide resistance evolution.
The yellow-headed parrot Amazona oratrix is categorized as Endangered on the IUCN Red List but little is known about its distribution, particularly along the Pacific coast of Mexico. We used ecological niche models, with presence records from museum collections and historical sightings, overlain on vegetation maps, to predict the historical range of the yellow-headed parrot along the Pacific coast of Mexico. We compared this with the current range of the species, estimated with ecological niche models using presence–absence data from surveys during 2003–2008. We estimate that the range of the yellow-headed parrot along Mexico’s Pacific coast has contracted by 79%. The current range may now cover only 18,957 km2, in three main areas. At one of these, a small isolated area on the coast of Jalisco, the species may be vulnerable to extirpation or genetic endogamy. There is a lack of conserved tropical semi-deciduous forest, which provides optimal habitat for reproduction of this parrot, within the current range of the species. Only the south, along the coast of Oaxaca, has extensive areas of this habitat. There are only three, small, protected areas within the species’ current range. Conservation strategies need to be implemented to restore connectivity between the three main areas of the current range of the yellow-headed parrot on the Pacific coast of Mexico.
Parrots represent a large biomass of canopy granivores in tropical forests, and may be effective pre-dispersal seed predators. We evaluated the importance of the lilac-crowned parrot (Amazona finschi) as a pre-dispersal seed predator of Astronium graveolens (Anacardiaceae) in tropical dry forest. Seeds were collected in fruit-traps beneath 22 trees to compare pre-dispersal seed predation by parrots and insects, and determine whether intensity of seed predation was related to fruit-crop size or the aggregation of fruiting conspecifics around focal trees. Ground-level exclosures were established to compare post-dispersal seed predation by vertebrates and insects. The lilac-crowned parrot predated 43% of seeds pre-dispersal, while insects predated only 1.3%. Intensity of pre-dispersal seed predation by parrots was significantly greater in high-fruiting 0.79-ha resource patches, and was not related to fruit abundance of the focal tree. Foraging parrots also discarded immature fruits below the tree, causing a total 56% pre-dispersal loss of seed production, which was greater than post-dispersal removal by vertebrates, mainly rodents (51%) or insects (36%). Our results show that parrots play an important role as pre-dispersal seed predators in tropical dry forests. The reduction of parrot populations in tropical forests may have consequences for seed predation, affecting recruitment patterns of canopy trees.
One hundred and three known sexual-contact pairs of patients with culture-proven gonorrhoea who attended St Mary's Hospital, London between May 1989 and February 1991 were identified. All isolates from these patients were serotyped and auxotyped and compared for type concordance within sexual-contact pairs. Serotype was concordant in 80 (78%) of 103 sexual-contact pairs, auxotype in 88 (85%) and auxotype/serovar (A/S) class in 66 (64%) on the first screening. All pairs of isolates showed concordance in both serotype and auxotype when typing was repeated using a single set of serotyping reagents and of auxotyping media. Seventeen serovars. 9 auxotypes and 36 A/S classes were found in this population. Our results suggest that both serotyping and auxotyping may be used as markers to allow tracing of sexual-contact pairs, but that a single set of reagents should be used to ensure maximum reliability.
Current methods to establish the duration of toxoplasma infection in pregnant women and for the diagnosis of toxoplasmosis in the neonate or HIV infected patient have significant limitations. We assessed the precision of a commercial ELISA for the detection of toxoplasma specific IgG and adapted the assay to measure avidity using an elution agent washing step. The sensitivity and specificity of the ELISA were 100 and 75 % respectively and optimal measurement of avidity was achieved using 6 M urea as the elution agent.
Toxoplasma lymphadenopathy of less than 3 months duration was associated with low avidity specific IgG but some discordant findings were recorded. Serial measurement of IgG avidity assisted the distinction between actively produced antibody in infants with congenital toxoplasmosis and passively acquired antibody of maternal origin in uninfected babies. There was no significant difference between avidity levels in HIV infected patients with or without cerebral toxoplasmosis.
During the last two years of the Great War the British government undertook a global propaganda campaign to generate support for the military advance into the Near East, British post-war domination of the region, and the war effort in general. The objective was to transform how the West and the peoples of the Ottoman empire perceived the Orient, its future, and the British empire. To fit with the international demand that the war should be fought for the cause of national self-determination, the Orient was re-defined as the Middle East: a region of oppressed nations that required liberation and tutelage by Britain and the entente. Great Britain was portrayed as the pre-eminent champion of the principle of nationality, which was behind its move into the Middle East. It is argued in this article that these narratives constituted a significant change in Western representations of the Orient and the British empire.
The objective of this paper is to provide glycaemic index (GI) and glycaemic load (GL) values for a variety of foods that are commercially available in the UK and to compare these with previously published values. Fasted subjects were given isoglucidic (50 or 25 g carbohydrate) servings of a glucose reference at least two to three times, and test foods once, on separate occasions. For each test food, tests were repeated in at least eight subjects. Capillary blood glucose was measured via finger-prick samples in fasting subjects (0 min) and at 15, 30, 45, 60, 90 and 120 min after the consumption of each test food. The GI of each test food was calculated geometrically by expressing the incremental area under the blood glucose response curve (IAUC) of each test food as a percentage of each subject's average IAUC for the reference food. GL was calculated as the product of the test food's GI and the amount of available carbohydrate in a reference serving size. The majority of GI values of foods tested in the current study compare well with previously published values. More importantly, our data set provides GI values of several foods previously untested and presents values for foods produced commercially in the UK.
Sporadic outbreaks of cyclosporiasis, a common cause of protracted diarrhoea in underdeveloped countries, are often undetected and undiagnosed in industrial countries. In May 2001, an outbreak of Cyclospora cayetanensis gastroenteritis was identified in British Columbia, Canada, with 17 reported cases. We conducted a case-control study involving 12 out of the 17 reported and confirmed case patients. Eleven (92%) of the patients had consumed Thai basil, an essential ingredient in Vietnamese cuisine, compared to 3 out of 16 (19%) of the control patients (P=0·003). Trace-back investigations implicated Thai basil imported via the United States as the vehicle for this outbreak. This is the first documented sporadic outbreak of cyclosporiasis linked to Thai basil in Canada, and the first outbreak of cyclosporiasis identified in an ethnic immigrant population. This outbreak provides the opportunity to increase our understanding of this emerging pathogen and improve on our prevention and control for future outbreaks.
It is unclear why intensive case management (ICM) failed to reduce hospitalisation in the UK700 trial.
To investigate outcome generation in the UK700 trial.
A qualitative investigation was undertaken in one UK700 centre.
Both intensive and standard case management practised individual casework, employed assertive outreach with comparable frequency, and performed similarly in the out-patient management of emergencies and inpatient discharge. However, ICM was advantaged in managing some noncompliance and undertaking casework that prevented psychiatric emergencies. Absence of team-based management and bureaucratised access to social care limited the impact of these differences on outcomes and the effective practice of assertive outreach, although this was relevant to only a sub-population of patients.
The impact of ICM was undermined by organisational factors. Sensitive anticipatory casework, which prevents psychiatric emergencies, may make ICM more effective than an exclusive focus on assertive outreach. Our findings demonstrate the value of qualitative research in evaluating complex interventions.