bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linking landscape patterns of resource distribution with models of aggregation in ovipositing stream insects
Authors: Lancaster Jill , Downes Barbara J. , Reich Paul 
Published: December 2004

Summary

Many species rely on resources that are discrete patches distributed across the landscape. Models of the coexistence of such taxa often require intraspecific aggregation of individuals on some patches, brought about by choices made during dispersal and patch location. Few studies have employed spatially explicit measures of dispersion to detect whether and how any aggregation of individuals is influenced by the dispersion of resource patches in natural landscapes.
For two species of caddisfly (Hydrobiosidae) in two stream stretches, we mapped the spatial distribution of potential and exploited patches (emergent rocks as oviposition sites) and enumerated egg masses on each rock. Point pattern analysis, based on Ripley's K‐function, was used to describe the spatial pattern of potential and exploited oviposition sites, and to test hypotheses about how site selection behaviour of females influences dispersion.
Emergent rocks were clumped and equally abundant in both stretches. As documented previously, egg masses of Ulmerochorema and Apsilochorema were aggregated within oviposition sites. Both species showed velocity‐specific preferences for oviposition sites: oviposition of Ulmerochorema occurred most often on rocks in fast flowing water (>0·30 m s−1); oviposition of Apsilochorema on rocks in slow water (<0·30 m s−1).
Our perception of how caddisflies deposit eggs into the stream landscape varied with the neutral landscape model. The most informative neutral landscape compared the spatial pattern of oviposition sites with the underlying pattern of emergent rocks, while constraining the random selection of rocks to reflect species’ velocity preferences. Oviposition sites of Ulmerochorema were clumped, over and above the background pattern of emergent rocks. Oviposition sites of Apsilochorema were over‐dispersed.
Hydrobiosid caddisflies appear to make decisions about egg‐laying at different scales. We propose a mechanistic explanation, based on what we know about the oviposition behaviour of these species, to explain how the observed patterns might arise. Our results emphasize the importance of quantifying resource patch use in natural (rather than artificial) landscapes.
Experimental manipulation of habitat structure: a retrogression of the small mammal succession
Authors: Fox Barry J. , Taylor Jennifer E. , Thompson Peter T. 
Published: December 2004

Summary

The habitat accommodation model for animal succession proposed that animal species enter a succession when changes in the vegetation succession reach a threshold of habitat suitable to that species. As the vegetation succession moves on, the habitat becomes less suited to that species and it is competitively excluded by species better suited to the habitat.
The main species in the mammalian succession following fire for wet heath in eastern Australia are rodents, with Pseudomys gracilicaudatus (eastern chestnut mouse) being followed by Rattus lutreolus (swamp rat) which becomes dominant with increasing time since fire. The abundance of both species has been shown to correlate with vegetation density, but in markedly different ways, and asymmetric interspecific competition has been demonstrated using controlled, replicated removal experiments in the field.
We used this system to examine if vegetation density is causal, manipulating the habitat by clipping to remove 60–70% of the vegetative cover from the 10 m × 10 m area surrounding each of six trapping stations on each grid. There were four experimental plots clipped, each with two abutting grids, one clipped and one unclipped, and a further four control plots each with two abutting grids that remained undisturbed.
We monitored the effects on each species with three censuses in January 1993 (summer) before clipping in early February, and on five further censuses, three in February (late summer) to assess immediate, short‐term effects, one in August (winter) and one in December 1993 (early summer).
The abundance of Rattus lutreolus was significantly reduced by clipping the vegetation, while the abundance of Pseudomys gracilicaudatus remained relatively unchanged by the clipping.
Two species that are abundant on early succession stages in dry heath succession, but occurred at very low abundance on these wet heath habitats before clipping, P. novaehollandiae (New Holland mouse) and Mus domesticus (house mouse), showed marked increases in abundance on clipped and control plots soon after clipping.
An abundance index based on the standardized difference between clipped and control plots, was used to assess responses to habitat manipulation. Rattus lutreolus demonstrated significant negative index values, Pseudomys gracilicaudatus had index values close to zero until the winter census, P. novaehollandiae and Mus domesticus showed positive abundance indices soon after clipping. The order of significant responses to the habitat manipulation was revealed as: Mus domesticus→Pseudomys novaehollandiae→ P. gracilicaudatus→ Rattus lutreolus.
The impact of a habitat manipulation experiment on these four species of rodents produced a retrogression of the small‐mammal succession. This demonstrated a causal role for vegetation density, which provided insight into the mechanisms that operate during the succession following fire, and supported the habitat accommodation model for animal succession.
Trophic facilitation by introduced top predators: grey wolf subsidies to scavengers in Yellowstone National Park
Authors: Wilmers Christopher C. , Crabtree Robert L. , Smith Douglas W. , Murphy Kerry M. , Getz Wayne M. 
Published: December 2004

Summary

The reintroduction of grey wolves Canis lupus (L.) to Yellowstone National Park provides a natural experiment in which to study the effects of a keystone predator on ecosystem function.
Grey wolves often provision scavengers with carrion by partially consuming their prey.
In order to examine how grey wolf foraging behaviour influences the availability of carrion to scavengers, we observed consumption of 57 wolf‐killed elk Cervus elaphus (L.) and determined the percentage of edible biomass eaten by wolves from each carcass.
We found that the percentage of a carcass consumed by wolves increases as snow depth decreases and the ratio of wolf pack size to prey size and distance to the road increases. In addition, wolf packs of intermediate size provide the most carrion to scavengers.
Applying linear regression models to the years prior to reintroduction, we calculate carrion biomass availability had wolves been present, and contrast this to a previously published index of carrion availability. Our results demonstrate that wolves increase the time period over which carrion is available, and change the variability in scavenge from a late winter pulse dependent primarily on abiotic environmental conditions to one that is relatively constant across the winter and primarily dependent on wolf demographics. Wolves also decrease the year‐to‐year and month‐to‐month variation in carrion availability.
By transferring the availability of carrion from the highly productive late winter, to the less productive early winter and from highly productive years to less productive ones, wolves provide a temporal subsidy to scavengers.
Declining survival rates in a reintroduced population of the Mauritius kestrel: evidence for non‐linear density dependence and environmental stochasticity
Authors: Nicoll M. A. C. , Jones Carl. G. , Norris Ken 
Published: December 2004

Summary

We studied a reintroduced population of the formerly critically endangered Mauritius kestrel Falco punctatus Temmink from its inception in 1987 until 2002, by which time the population had attained carrying capacity for the study area. Post‐1994 the population received minimal management other than the provision of nestboxes.
We analysed data collected on survival (1987–2002) using program MARK to explore the influence of density‐dependent and independent processes on survival over the course of the population's development.
We found evidence for non‐linear, threshold density dependence in juvenile survival rates. Juvenile survival was also strongly influenced by climate, with the temporal distribution of rainfall during the cyclone season being the most influential climatic variable. Adult survival remained constant throughout.
Our most parsimonious capture–mark–recapture statistical model, which was constrained by density and climate, explained 75·4% of the temporal variation exhibited in juvenile survival rates over the course of the population's development.
This study is an example of how data collected as part of a threatened species recovery programme can be used to explore the role and functional form of natural population regulatory processes. With the improvements in conservation management techniques and the resulting success stories, formerly threatened species offer unique opportunities to further our understanding of the fundamental principles of population ecology.
Strong context‐dependent virulence in a host–parasite system: reconciling genetic evidence with theory
Authors: Brown Mark J. F. , Schmid‐Hempel Regula , Schmid‐Hempel Paul 
Published: December 2004

Summary

Parasites can have dramatic effects on the ecology of their hosts. Such strong host–parasite interactions are the result of either parasites with generally high virulence, or generally benign parasites that nevertheless express context‐dependent virulence. Theoretically, one indication that an apparently benign parasite nevertheless has a large impact on its host should be the existence of strong genotypic interactions between host and parasite.
Crithidia bombi (Trypanosomatidae) is a highly prevalent but generally benign gut parasite of the bumble‐bee Bombus terrestris. The demonstration of strong genotypic interactions between C. bombi and B. terrestris, however, suggests that context‐dependent virulence may have a large impact on the host population. We thus investigated the effects of C. bombi across the entire life cycle of its host, including the stressful times of hibernation and colony‐founding. Owing to the high prevalence and rates of transmission of the parasite in field populations, we used a large‐scale laboratory experiment.
Under stressful hibernation, infected queens lost more mass. Infection also significantly reduced colony‐founding success, colony size, male production and overall fitness, by up to 40%. These findings show that strong genotypic host–parasite interactions may indeed be a reliable indicator that apparently benign and highly prevalent parasites are nevertheless exerting a dramatic impact on their host populations.
Estimating natal dispersal movement rates of female European ducks with multistate modelling
Authors: Blums Peter , Nichols James D. , Hines James E. , Lindberg Mark S. , Mednis Aivars 
Published: December 2004

Summary

We used up to 34 years of capture–recapture data from about 22 100 new releases of day‐old female ducklings and multistate modelling to test predictions about the influence of environmental, habitat and management factors on natal dispersal probability of three species of ducks within the Engure Marsh, Latvia.
The mean natal dispersal distances were very similar (c. 0·6–0·7 km) for all three species and were on average 2·7 times greater than breeding dispersal distances recorded within the same study system.
We were unable to confirm the kinship hypothesis and found no evidence that young first‐nesting females nested closer to their relatives (either mother or sister) than to the natal nest.
Young female northern shovelers, like adults, moved from small islands to the large island when water level was high and vice versa when water level was low before the construction of elevated small islands. Movement probabilities between the two strata were much higher for young shovelers than adults, suggesting that young birds had not yet developed strong fidelity to the natal site. Movements of young female tufted ducks, unlike those of shovelers, were not dependent on water level fluctuations and reflected substantial flexibility in choice of first nesting sites.
Data for young birds supported our earlier conclusion that common pochard nesting habitats in black‐headed gull colonies were saturated during the entire study period. Young females, like the two adult age groups, moved into and out of colonies with similar probability. Fidelity probability of female pochards to each stratum increased with age, being the lowest (0·62) for young (DK) females, intermediate (0·78) for yearlings (SY) and the highest (0·84) for adult (ASY) females.
Young female tufted ducks, like adults, showed higher probabilities of moving from islands to emergent marshes when water levels were higher both before and after habitat management. The relationship between the spring water levels and movement was much weaker for young females than for adults.
Young female diving ducks exhibited much stronger (compared to adults) asymmetric movement with respect to proximity to water, with higher movement probabilities to near‐water locations than away from these locations.
Local survival of day‐old ducklings during the first year of life was time‐specific and very low (means for different strata/states 0·01–0·08) because of high rates of emigration and prefledging mortality.
The population dynamical implications of covert infections in host–microparasite interactions
Authors: Boots Michael , Greenman Jon , Ross David , Norman Rachel , Hails Rosie , Sait Steven 
Published: December 2004

SummaryThe persistence of parasites that are only seen in intermittent outbreaks has intrigued ecologists. Long the subject of speculation, there is now evidence that viral insect diseases can cause covert as well as overt infections.Typically, infection leads to overtly diseased individuals that are infectious and die as a result of the disease, but it can also produce other individuals that show a covert, non‐infectious pathology, which is typically asymptomatic. Covertly infected individuals do not die as a result of infection, although they may be affected sublethally such that their reproductive output falls, they may transmit the covert infection vertically and, crucially, they may convert at some rate to overt infectious individuals. In this way the parasites are able to persist in host populations and can be detected only by the use of molecular techniques.Here, we apply novel analytical techniques to a general host–parasite modelling framework and examine the population dynamical consequences of such covert infections.The interplay between various stabilizing and destabilizing forces leads to a highly complex pattern of host dynamics, including a theoretically intriguing pinch point. Covert infections may be stabilizing or destabilizing depending on the specific characteristics of the interaction, particularly in relation to the rate of conversion from covert to overt infection.In general terms, intermediate rates of conversion are stabilizing, while high and low rates may each destabilize the host population. In contrast, there is no consistent pattern for the role of vertical transmission because, in some cases, high levels are stabilizing while in others they are destabilizing.Thus, our results demonstrate that relatively subtle pathogen effects such as covert infections can have important and novel dynamical impacts on the host–pathogen interaction. It also suggests that the effects of covert infection are likely to be system‐specific and information may be required on a system‐by‐system basis in order to make predictions.
Caddisfly diapause aggregations facilitate benthic invertebrate colonization
Authors: McCabe Declan J. , Gotelli Nicholas J. 
Published: December 2004

Summary

We used natural and manipulative field experiments to examine the effects of caddisfly (Trichoptera) diapause aggregations on benthic macroinvertebrates communities in a Vermont river.
Natural substrates with aggregations of Neophylax and Brachycentrus (Trichoptera: Uenoidae and Brachycentridae) had higher species richness than did substrates lacking aggregations. Aggregations of caddisfly cases added to artificial substrates (bricks) also accumulated greater abundance, species density (number of species per unit area), and species richness (number of species per standard number of individuals) than did control bricks.
Low‐density, uniformly spaced, Brachycentrus cases accumulated higher species density and species richness than did an equivalent density of clumped cases. Similarly, empty Neophylax cases accumulated higher diversity than did cases still occupied by Neophylax pupae.
Although natural substrates had higher species richness than artificial substrates, substrate type did not change qualitatively the effect of caddisfly aggregations on species richness.
We subsampled individuals randomly from aggregations and control surfaces to provide an estimate of species richness unbiased by abundance. Expected species richness was higher in aggregations than on control surfaces. These results suggest that caddisfly aggregations increase species density by altering the shape of the species–abundance distribution as well as by accumulating individuals and species passively.
We conclude that caddisfly diapause aggregations increase habitat complexity and facilitate colonization of other benthic species.
Literacy, readability and cultural barriers: critical factors to consider when educating older African Americans about anticoagulation therapy
Authors: Wilson Feleta L. , Racine Eric , Tekieli Virginia , Williams Barbara 
Published: December 2004

Summary • The number of patients on anticoagulation therapy has increased dramatically over the past two decades. Yet, few studies have examined the psychosocial barriers of low literacy, culture and inappropriate patient education materials used to teach older African Americans about their anticoagulation therapy. • The aims of this study were to investigate literacy levels among older patients, and evaluate the readability and determine the cultural sensitivity of written information used in an anticoagulation management clinic. • A descriptive, correlational design was used. Patients' (n = 62) knowledge levels and the readability and cultural sensitivity of written materials were examined. The Rapid Estimate of Adult Literacy in Medicine (REALM) was used to measure reading skills of patients, while the SMOG formula (a formula for assessing readability) was used to test the readability of written educational materials used in an Anticoagulation Management Clinic. A Knowledge Information Profile, developed for this study by one of the authors (Wilson), was used to measure patient knowledge about warfarin, medication side‐effects and food sources of vitamin K. A modified, culturally sensitive and easy‐to‐read pamphlet was used as an alternative teaching tool in the study. • The results of the study revealed the average self‐reported for highest grade completed in school was twelfth grade; however, the actual mean reading skills were between seventh and eighth grade. The readability of the written information was three to four grades higher than patients' reading abilities. None of the patient education materials were culturally sensitive. • This study underscores the importance of having information that is understandable and culturally relevant to prevent the outcome of internal bleeding. Nurses have a vital role in educating patients and ensuring that teaching materials are appropriate for the target population.
Implementing aromatherapy in nursing and midwifery practice
Authors: Rawlings Fran , Meerabeau Liz 
Published: December 2004

Summary• This paper reports the results of a small qualitative study of nurses and midwives who had undertaken a course in aromatherapy, one of the most popular complementary therapies in the UK. In particular, it examines barriers to putting their knowledge into practice.• Participants had completed the aromatherapy course between 9 months and 2 years previously, and worked in a variety of settings. All were approached via their employing NHS trust.• The interviews which took place in the clinical area were tape recorded and generally lasted for about 40 minutes.• Data were analysed using the procedure outlined by Colaizzi (1978) Significant statements were clustered into themes, guided by whether they had a ‘look alike/feel alike’ quality, and were subsequently validated with the informants.• The main themes discussed in this paper are the personal and professional benefits that respondents reported from undertaking the course, organizational issues and the frustrations they experienced because of delays in implementing changes in practice.
Having a child with asthma – quality of life for Swedish parents
Authors: Dalheim‐Englund Ann‐Charlotte , Rydström Ingela , Rasmussen Birgit Holritz , Möller Christian , Sandman Per‐Olof 
Published: December 2004

Background.  Asthma is the most common chronic childhood disease. Childhood asthma contributes significantly to morbidity among children and has a significant impact on the quality of life (QoL) and daily routines of both the children and their parents.Aim and objective.  The purpose of this study was to investigate how Swedish parents of children with asthma experience their QoL, and to investigate whether there were differences concerning QoL between parents within the same family. The purpose was also to investigate possible connections between their QoL and background variables.Method.  A total of 371 parents of children with asthma (57% mothers and 43% fathers) participated in the study. The Paediatric Asthma Caregiver's Quality Of Life Questionnaire (PACQLQ) was used to measure the parents’ QoL, i.e. how the child's asthma interferes with the parents’ normal activities and how it has made them feel.Results.  The findings show that most parents of children with asthma evaluated their QoL as close to the positive end of the scale, and there was close agreement in the scoring between parents within the same family. Significant associations were found between parents’ lower QoL outcome and living in the North of Sweden. There were also significant associations between fathers’ lower QoL outcome and having a child younger than 13 years of age and mothers’ lower QoL outcome and having a child with severe asthma. Although the result shows that a child's asthma did not influence the parents’ QoL to a greater degree, it is still important for healthcare workers to help these parents to sustain and improve their well‐being.Conclusions.  The fact that they just evaluated their QoL during the preceding week only, and did so at the time when their children were being treated with asthma medication, might have influenced the results in a positive direction.