bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting invasions: alternative models of human‐mediated dispersal and interactions between dispersal network structure and Allee effects
Authors: Chivers Corey , Leung Brian 
Published: October 2012

Summary
Human‐mediated dispersal has been shown to be the most important vector for the spread of invasive species, yet there has been little evaluation of alternative models of dispersal in terms of differences in their predictions of invasion patterns. Moreover, no analyses have been attempted to elucidate the potential interaction between alternative models of human‐mediated dispersal and population dynamical characteristics, such as Allee effects, which are central to the probability of an invasion.
Two prominent models in the literature which have previously been employed to predict human movement patterns are explored: (i) gravity models, which use the attractiveness of and distance to a location to predict travel patterns, and (ii) random utility models, which assume that individuals decide where to travel by maximizing the benefits that they receive according to some partially observable function of individual and site characteristics.
While distinction is often drawn between them in the literature, we demonstrate that these two approaches can be reduced to alternative functional forms describing the trip‐taking decisions of individuals.
Each model was empirically parameterized using a survey of recreational boaters in Ontario, Canada. Within each model, both boater‐ and site‐specific characteristics were important and the functional form provided by the gravity model was significantly better at capturing the behaviour of recreational boaters
Synthesis and applications. The dispersal and establishment of species into novel habitats are central components of the invasion process and of quantitative risk assessments. However, predictions are dependent on the estimated spatial structure of the dispersal network and its potential interactions with species characteristics. This study demonstrates that Allee effects can interact with dispersal network structure to significantly alter predicted spread rates and that the consequences of these interactions manifest differently at the system and site levels. This modelling framework can be used to inform management interventions aimed at modifying human‐mediated dispersal to reduce the spread of invasive species.
Role of domestic shipping in the introduction or secondary spread of nonindigenous species: biological invasions within the Laurentian Great Lakes
Authors: Briski Elizabeta , Wiley Chris J. , Bailey Sarah A. 
Published: October 2012

Summary
The most effective way to manage invasive species is to prevent their introduction via vector regulation. While progress has been made in the management of transoceanic ballast water, domestic vessels operating within smaller geographic regions such as the Laurentian Great Lakes, Mediterranean Sea, North Sea or Baltic Sea are often exempt from regulations.
We randomly surveyed unmanaged ballast water moved by domestic vessels within the Laurentian Great Lakes and compared the results with that of exchanged ballast water from transoceanic vessels to assess invasion risk of zooplankton transported by these two types of vessels.
Total abundance and species richness were significantly different between the two vessel types with mean abundance being two magnitudes greater, and species richness being threefold higher in domestic vessels compared with transoceanic vessels. Abundance of restricted taxa – cumulatively the Great Lakes' indigenous and nonindigenous species (NIS) which do not occur in all five lakes – was also significantly higher in domestic vessels (mean densities were 24 170 and 3421 individuals per m3 for domestic and transoceanic vessels, respectively), whereas the abundance of NIS did not differ between vessels (median densities of 2015 and 850 individuals per m3, respectively).
We documented 89 species transported by domestic vessels of which 31 had restricted distribution and eight were NIS. While most NIS were already established in all five lakes, Cercopagis pengoi, a NIS of global concern, and Nitokra hibernica have not been identified from Lake Superior, and both were sampled from ballast water destined for discharge in Lake Superior. Beside the risk of spread of NIS between lakes, domestic shipping can act as a vector for homogenization of indigenous taxa, with at least 21 native species (99 events) being moved outside their historical distribution.
Synthesis and applications. Our study indicates that management of invasive species should consider ecological, not geographical or political boundaries. Domestic vessels operating within a limited geographic region have high potential to introduce or spread species with restricted distribution, demonstrating importance of intraregional ballast water management. Results presented here should interest policy makers and environmental managers who seek to reduce invasion risk.
Rigorous gharial population estimation in theChambal: implications for conservation and management of a globally threatened crocodilian
Authors: Nair Tarun , Thorbjarnarson John B. , Aust Patrick , Krishnaswamy Jagdish 
Published: October 2012

SummaryIndia'sChambalRiver hosts the largest population of the critically endangered gharial. Boat‐based daylight surveys to date only provide indices of relative abundance, without measures of survey bias or error. No attempt to quantify detection probabilities in these surveys has yet been made, and thus, absolute density estimates of this population remain unknown.We surveyed 75 km of theRiverChambal and photographed individual gharials for capture–recapture analysis. The total sampling effort yielded 400 captures. Population closure was supported (z = −1·48,P = 0·069), and closed‐population models were used to estimate abundances.Models were selected using theAkaikeInformationCriterion (AIC) index of model fit. The best model estimated 231 ± 32 adult, 83 ± 23 subadult and 89 ± 19 juvenile gharials (Mean ± SE), respectively, while the model‐averaged estimate was 220 ± 28 adult, 76 ± 16 subadults and 93 ± 16 juvenile gharials, respectively.The best model estimated absolute densities of 3·08 ± 0·43, 1·11 ± 0·3 and 1·19 ± 0·25 adult, subadult and juvenile gharials km−1, respectively, while the model‐averaged estimate was 2·93 ± 0·37, 1·01 ± 0·21 and 1·24 ± 0·21 adult, subadult and juvenile gharials km−1, respectively, compared with relative densities of 0·94, 0·45 and 0·30 adult, subadult and juvenile gharials km−1, respectively, from boat‐based daylight surveys. On the basis of our best model, we suggest a detection probability based correction factor of 3·27, 2·47 and 3·97 to boat‐based daylight survey estimates of adult, subadult and juvenile gharials, respectively.Synthesis and applications. Used within the framework of capture–recapture analysis, photoidentification provides a reliable and noninvasive method of estimating population size and structure in crocodilians. We also opine that without determining the current status of gharials, highly intensive strategies, such as the egg‐collection and rear‐and‐release programmes being implemented currently, initiated on the basis of underestimates of population sizes, are unwarranted and divert valuable conservation resources away from field‐based protection measures, which are essential in the face of threats like hydrologic diversions, sand mining, fishing and bankside cultivation.
Using water residency time to enhance spatio‐temporal connectivity for conservation planning in seasonally dynamic freshwater ecosystems
Authors: Hermoso Virgilio , Ward Doug P. , Kennard Mark J. 
Published: October 2012

SummaryAddressing spatial connectivity in conservation planning is important to ensure the maintenance of patterns and processes needed to support the persistence of biodiversity. In freshwater ecosystems, spatial connectivity is constrained by the presence of water, which exhibits marked temporal changes in regions with wet–dry seasonal climates. Previous studies have focused on spatial connectivity and overlooked the temporal component, which is required for the functionality of spatial connections (because of temporal changes in water availability).We identify priority areas for the conservation of freshwater fish, waterbirds and turtles in theMitchellRiver catchment in the wet–dry tropics of northernAustralia. We demonstrate how adequacy of freshwater conservation can be enhanced by integrating an estimate of water residency time (WRT) into the prioritization process.WRTreflects refugial potential and connectivity in freshwater ecosystems and was quantified usingModerateResolutionImagingSpectroradiometer (MODIS) flood and post‐floodLandsat satellite imagery. We compare the spatial allocation of priority areas and the spatial and temporal connectivity under two alternative scenarios: (i) accounting only for spatial connectivity and (ii) integrating spatial and temporal connectivity.Priority areas identified under the spatial and temporal connectivity scenario showed a 40% increase inWRTvalues with respect to the traditional spatial connectivity scenario. This was achieved at no additional cost in terms of total protected area and maintaining the same spatial connectivity.Despite priority areas identified under the two alternative scenarios showing intermediate spatial overlap (64%), the selection process was more efficiently biased towards planning units with highWRTvalues.WRTin planning units that were only selected under the temporal connectivity scenario was 2·5 times higher than in planning units that only appeared in the traditional connectivity scenario. This reveals the importance of accounting forWRTwhen identifying freshwater priority areas in wet–dry seasonal environments.Synthesis and applications: Considering the temporal connectivity in conservation prioritization as we propose here helps to assess periods of longest spatial connections, thereby maximizing the refugial role of freshwater priority areas during dry periods. Using publicly available satellite imagery data and software, our approach allows improved management of aquatic resources and biodiversity during periods of water scarcity, which may increase in incidence and duration with climate change.
Combining multi‐scale socio‐ecological approaches to understand the susceptibility of subsistence farmers to elephant crop raiding on the edge of a protected area
Authors: Guerbois Chloé , Chapanda Eunice , Fritz Hervé 
Published: October 2012

Summary

Coexistence between subsistence farmers and elephants leads to problems for conservation and food security, especially on the edge of protected areas. Crop‐raiding patterns have been investigated for decades, but understanding both social and ecological determinants remains a key challenge to defining realistic management options in a context of increasing human and elephant densities.
Hwange National Park, Zimbabwe, and its periphery, hosts one of the highest densities of free‐ranging elephants. As scale is a critical element of ecological systems, we analysed the determinants of crop raiding at three spatial scales: the study area (217 households in 200 km²), the village (30 fields in 14 km²) and the edge of the refuge area (30 fields in less than 3 km²). We combined foraging ecology with sociological approaches, including a participatory experiment, to understand the processes behind the susceptibility of subsistence farmers to crop raiding.
Distance to refuge area was the most influential determinant in decreasing crop‐raiding risk, with no damage occurring further than 4·4 km. We obtained consistent models between the three scales with high explanatory power for field damage at village and edge scales (94% and 68% respectively). Household density acted as an obstacle to elephants. Millet patches seemed to provide refuges, and thus promoted damage.
The participatory experiment allowed rigorous testing of the efficiency of traditional guarding practices. The presence of people was crucial for guarding efficiency. More innovatively, we demonstrated the role of neighbours and the importance of cohesive guarding as a promising strategy of reducing crop loss at the edge, primarily in areas with a high density of elephant paths.
Synthesis and applications. This paper provides evidence that multi‐scale multidisciplinary approaches can unravel endogenous processes shaping human–elephant coexistence on the edge of protected areas. We believe that manipulating perceived risks for elephants, through mitigation methods based on the ‘ecology of fear’, and spatial organization of households, could create a ‘soft fence’ which, when combined with adequate incentives to farmers, promotes a better integration of the protected area in its territory.
Carry‐over effects of spring hunt and climate on recruitment to the natal colony in a migratory species
Authors: Juillet Cédric , Choquet Rémi , Gauthier Gilles , Lefebvre Josée , Pradel Roger 
Published: October 2012

Summary

In long‐lived species, temporal variation in recruitment, defined as the entry of new individuals into the breeding population, can have a large effect on population growth rate. While hunting, as a management tool, is generally expected to control population size via increased mortality, it may also act by affecting recruitment. Although the impact of hunting on survival is well studied, less attention has been paid to the non‐lethal impacts of hunting on recruitment.
To control the population size of the greater snow goose Chen caerulescens atlantica, an overabundant arctic‐nesting species, a spring hunting season was implemented from 1999 onwards in addition to the traditional autumn and winter hunting seasons. We investigated the potential carry‐over effect of spring hunting on recruitment of females to their natal colony on Bylot Island, Nunavut, Canada from 1992 to 2005 while accounting for other potential confounding factors, primarily climatic effects.
We applied a multistate capture‐Mark‐Recapture recruitment model to a dataset of known‐age individuals (n = 12 100), combining live recaptures at the breeding colony with dead recoveries from hunters.
Annual variation in recruitment probability was best explained by spring hunt and a synthetic variable combining the climatic conditions experienced during migration (extreme values of the North Atlantic Oscillation index) with conditions upon arrival at the breeding grounds (snow cover). This model accounted for 58% of the temporal variation in recruitment, while the harvest rate or the climatic index taken alone accounted for 38% each. In the year with the highest spring hunting pressure (adult harvest rate ≈6%), recruitment was reduced by up to 50% compared to years with no hunt and similar average climatic conditions.
Synthesis and applications. We conclude that there was a negative impact of the spring hunt not only on survival but also on recruitment in greater snow geese. These non‐lethal effects of hunting must be considered in management decisions aimed at controlling overabundant populations where recruitment is an important driver of population growth, as occurs in geese. Our study is also relevant to other situations such as in threatened species still exposed to hunting, as consideration of non‐lethal effects of hunting may be critical for their conservation.
Epiphytic bryophytes near forest edges and on retention trees: reduced growth and reproduction especially in old‐growth‐forest indicator species
Authors: Löbel Swantje , Snäll Tord , Rydin Håkan 
Published: October 2012

Summary

Epiphytes are an important component in many forest ecosystems. The proportion of threatened epiphyte species is high, and the impact of clearcuts on key demographic processes via edge‐influence is still poorly understood. There are few studies on epiphyte growth, and even less is known about how reproduction is affected by proximity to forest edges. For retention trees, demographic studies are even scarcer.
Based on the results from a 6‐month transplant experiment and a 3‐year study of natural colonies, we modelled growth and reproduction of epiphytic bryophytes used as indicators of old‐growth forests and widespread epiphytes in relation to distance from the forest edge. We also modelled growth and reproduction on retention trees within the clearcut. Species responses were linked to variation in canopy openness.
Unlike the widespread species, the old‐growth‐forest indicators grew exponentially with distance from the edge, and this response was more pronounced at the south‐east than north‐west forest edge. In one red‐listed species, reproduction was thoroughly inhibited near the edge, whereas the reproductive rate of the widespread species tended to increase. However, the widespread species also showed reduced shoot lengths on the retention trees.
Reduced growth and inhibited reproduction of sensitive epiphytes near edges decrease the number of dispersing diaspores and may, in combination with lower local connectivity and increased tree fall rates close to edges, increase the risk of metapopulation extinction.
Synthesis and applications. Two general management implications for boreal forests are drawn. First, retention trees may not have the capacity to act as a ‘lifeboat’ for epiphytic bryophytes and support their populations during the regeneration phase. Second, the creation of buffer zones is a useful conservation strategy for bryophytes. The exact width of zones depends on the forest structure and should be orientated in relation to the requirements of the most sensitive species. For the rather dense experimental forest, a width of at least 30 m was required for the south‐facing buffer, whereas for the north‐facing buffer 10 m was sufficient.
The role of dispersal levels, Allee effects and community resistance as zooplankton communities respond to environmental change
Authors: Gray Derek K. , Arnott Shelley E. 
Published: October 2012

Summary

Worldwide, freshwater zooplankton communities have been subjected to multiple environmental stressors including acidification, invasive species introductions, habitat alteration and climate change. Understanding the factors that affect zooplankton community responses in the face of environmental change is an important goal if ecologists expect to make predictions regarding the impact of current and future stressors. The acidification and recovery of lakes provides a well‐studied example of the impacts of environmental change.

For this study, we conducted a field enclosure experiment using zooplankton communities that are recovering from the effects of acidification to determine whether dispersal levels, Allee effects and biotic interactions could influence comˋmunity responses as pH levels increase. The experiment involved the introduction of four acid‐sensitive colonist species (Daphnia retrocurva, Skistodiaptomus oregonensis, Epischura lacustris and Tropocyclops extensus) into enclosures stocked with recipient communities. The experiment was a factorial design with colonists introduced at three starting densities (low, medium and high) and enclosures being stocked with either diverse communities typical of neutral lakes or relatively depauperate communities dominated by the acid‐tolerant copepod Leptodiaptomus minutus. Per capita growth rates (r) for colonist species were measured by sampling communities in enclosures over a 10‐week period. Factorial anovas were conducted to determine whether r differed according to starting densities, recipient community type or their interaction.

Our results indicated that r for the copepods E. lacustris and S. oregonensis were greater when introduced at high initial densities, suggesting an Allee effect based on mate limitation. In addition, r for S. oregonensis was lower when introduced to acid communities, suggesting biotic interactions with the resident community were important for this species. Per capita growth rates for T. extensus and D. retrocurva did not differ among treatments.

Synthesis and applications. These results suggest that community response to environmental change can be influenced by dispersal, Allee effects and community interactions. Studies evaluating the ongoing recovery of zooplankton communities from acidification, or their response to other stressors, should take these factors into account. If rapid community responses are desired, dispersal rates for sexual zooplankton species (copepods) may need to be artificially increased.
Supporting deployed operations: are military nurses gaining the relevant experience from MDHUs to be competent in deployed operations?
Authors: Beaumont Steven P , Allan Helen T 
Published: October 2012

Aims and objectivesTo explore how peacetime employment of military nurses in the UK National Health Service Medical Defence Hospital Units prepares them to be competent to practise in their role on deployment.BackgroundMilitary secondary care nurses are employed within UK National Health Service Trusts to gain clinical experience that will be relevant to their military nursing role.DesignA two‐stage grounded theory study using mixed methods: postal questionnaire survey and in‐depth interviews.MethodsIn stage one a postal questionnaire was distributed to all serving military nurses. Stage two involved 12 semi‐structured interviews. The data from both parts of the study were analysed using grounded theory.ResultsFour categories and one core category were identified, which suggested that participants did not feel fully prepared for deployment. Their feelings of preparedness increased with deployment experience and decreased when the nature of injuries seen on deployment changed. Respondents argued that even when unprepared, they did not feel incompetent. The findings suggest that the peacetime clinical experience gained in the National Health Service did not always develop the necessary competencies to carry out roles as military nurses on deployment. This study highlights the unique role of military nurses. We discuss these findings in the light of the literature on competency and expertise.ConclusionThe military nurses in this study did not feel fully prepared for deployed operations. We propose a new model for how military nurses could gain relevant experience from their National Health Service placements.Relevance to clinical practiceNational Health Service clinical placements need to be reassessed regularly to ensure that they are meeting military nurses' clinical requirements. Experiences of nurses returning from deployment could be shared and used as a basis for reflection and learning within National Health Service Trusts and also inform decisions regarding the appropriateness of clinical placements for qualified military nurses.