bluuebunny/crossref_metadata_2025_split huggingface dataset:
A general framework for the aggregation model of coexistence
Authors: Hartley Stephen , Shorrocks Bryan 
Published: March 2003

SummaryThe aggregation model of coexistence has been used widely to explain the coexistence of competing species that utilize patchy and ephemeral resources. Over the years, it has been reformulated in many different ways, using different assumptions, indices and analyses, leading sometimes to contradictory conclusions. We present a general framework, from which many of the alternative approaches are derived as special cases.A generalized distribution, composed of the distribution of visits across patches and the distribution of eggs per visit, is used to model changes in the mean individual‐level experience of density that occur at different population‐level densities.New and more general criteria for coexistence are derived, based upon standard invasability analysis of Lotka–Volterra competition equations applied to a patchy system.An important parameter in the new coexistence criteria is the mean per capita density of individuals in a single clutch (). Until now this measure has been relatively ignored, experimentally and theoretically.We confirm earlier findings that the random distribution of clutches may be a sufficient cause of aggregated egg distributions to allow coexistence between species of unequal competitive ability, but only if the product of competition coefficients is less than one.
Foraging ranges of solitary bees
Authors: Gathmann Achim , Tscharntke Teja 
Published: March 2003

Summary

Habitat requirements of solitary bees include nesting sites, food resources and nesting material. We used translocation experiments to establish foraging distances and measured foraging trip duration to analyse how solitary bees cope with the distance between nesting sites and suitable food plants in different habitat types.
Maximum foraging distance between nesting site and food patch was 150–600 m for the 16 bee species examined. Foraging distance was correlated positively with body length. Mean foraging trip duration, measured for seven bee species, ranged from 6 to 28 min and was also correlated with body length. In a study of the polylectic species Osmia rufa
, we found a significant decrease in foraging trip duration with increasing number of plant species. Logistic regressions showed that the oligolectic
Megachile lapponica
nested in trap nests with a probability of 50% if the distance between trap nest and food patch was less than 250 m. The oligolectic
Chelostoma rapunculi utilized trap nests when the distance to the nearest food patch was less than 300 m.
These experiments showed that solitary bees have a rather small foraging range so local habitat structure appears to be of more importance than large‐scale landscape structure. All requirements for sustaining viable populations must be within this range. Therefore, it is necessary to maintain and restore a dense network of habitat patches in landscapes to ensure long‐term sustainability of wild bee diversity and their ecological function as pollinators.
Reduced applications of metaldehyde pellets for reliable control of the slug pests Arion lusitanicus and Deroceras reticulatum in oilseed rape adjacent to sown wildflower strips
Authors: FRIEDLI JÜRG , FRANK THOMAS 
Published: March 2003

Summary

Slugs have been shown to cause severe damage in oilseed rape crops adjacent to sown wildflower strips. Rape can be protected from this damage by broadcasting a recommended dose of metaldehyde over the whole field area. This paper investigates whether severe slug damage can be prevented by applications of metaldehyde just along the wildflower strips thereby reducing the input of chemical molluscicide.
In this study, untreated control plots suffered severe crop loss at 1 m from all wildflower strips studied. However, all treatments of molluscicide protected rape from severe crop loss without significant differences among the three treatments (two different concentrations of metaldehyde applied in 50‐cm wide barriers along the strips and a recommended dose of metaldehyde broadcast over the whole study area).
Arion lusitanicus and Deroceras reticulatum were by far the most abundant slug pests found in the studied rape fields. Arion lusitanicus was very abundant in the wildflower strips and up to 1 m into the field; however, it was almost entirely absent at 3 m from the strips. Since D. reticulatum was evenly distributed over the whole field area, A. lusitanicus appeared to be responsible for the majority of damage in control plots 1 m from the wildflower strips.
Application of metaldehyde in a 50‐cm wide band has been shown to be practicable and efficient in protecting rape from severe slug damage near to wildflower strips. These reduced applications of molluscicide mean savings of time and money for farmers and can be recommended for practical application.
Long‐term changes in agricultural practices and wildfowling in an internationally important wetland, and their effects on the guild of wintering ducks
Authors: Duncan P. , Hewison A. J. M. , Houte S. , Rosoux R. , Tournebize T. , Dubs F. , Burel F. , Bretagnolle V. 
Published: March 2003

1. The Marais Poitevin, one of the principal wintering and passage sites for ducks and waders in the East Atlantic flyway, underwent agricultural intensification in the 1980s. The numbers of ducks declined in the period 1979–96 in the main roost, Baie de l’Aiguillon; this was a site‐specific phenomenon for which local factors were responsible. We describe here long‐term changes in some key characteristics of the wetlands, paying particular attention to the principal factors affecting the quality of waterbird habitat: the area of semi‐natural grasslands, water management and wildfowling. 2. The area of grasslands declined by 50% between 1970 and 1995, principally as a result of conversion to arable farmland. The pattern was observed over the whole area and was slightly more marked close to the day‐roost of the ducks. The rate of change was greatest in the 1980s. Water levels, and therefore the flooded area, were reduced over the study period during the months of May to November. The numbers of wildfowlers declined from the 1970s, but the number of artificial wildfowling ponds increased, especially after 1980. The number of birds killed did not decline and may have increased. The quality of the ducks’ habitat therefore declined by all three measures. 3. Four species, mallard, shoveler, teal and gadwall, showed an increase in other sites in north and west France either over the whole period or over the last part (1984–96), while declining (shoveler and mallard) or remaining stable in the Baie de l’Aiguillon. Pintail remained stable in the other sites, while showing a long‐term decline (over 30 years) in the Baie. Wigeon did not use the Baie in large numbers in the 1996 cold spell as they did until the 1980s. 4. The uncoupling of the trends for these species in the Baie from their trends in the other sites may reflect the loss of grassland feeding habitat in the Marais Poitevin. However, for mallard, pintail and shoveler the declines in the Baie were much stronger than the 50% loss of grasslands so other factors, such as the reduction in autumn flooding and/or shooting, are likely to have played a part. 5. Since the three measures of long‐term trends in duck habitat co‐varied it was not possible to separate their effects statistically. The hypotheses arising from this study need to be tested: this should be done using comparative and experimental approaches. Suggestions are made for the management of water levels and shooting in the feeding habitat close to the Baie de l’Aiguillon.
Prediction of weed density: the increase of error with prediction interval, and the use of long‐term prediction for weed management
Authors: Wallinga J. , Grasman J. , Groeneveld R. M. W. , Kropff M. J. , Lotz L. A. P. 
Published: March 2003

1. This paper addresses the errors that are associated with the long‐term prediction of weed densities, and the effect of these errors on the performance of weed management decisions based on those long‐term predictions. 2. A model of weed population dynamics was constructed and its parameters were estimated from experimental observations of population dynamics of the weed species Stellaria media in a crop rotation. 3. The observations showed that estimates of weed population growth rate differed between two locations. 4. The model was used to analyse error propagation for predicted weed densities in an enlarged prediction interval. It is concluded that errors due to an uncertain population growth rate increase linearly with the length of the prediction interval, and thus pose an upper limit to the horizon for long‐term predictions. 5. It is shown that a limited ability to predict weed densities does not necessarily impair the practical use of weed population dynamic models in planning for long‐term weed control programmes.
Recent rise to dominance of Molinia caerulea in environmentally sensitive areas: new perspectives from palaeoecological data
Authors: Chambers F.M. , Mauquoy Dmitri , Todd Pamela A. 
Published: March 2003

Summary 1. A characteristic of some heath and moorland areas in maritime north‐west Europe is the widespread dominance of Molinia caerulea (purple moor grass). The overwhelming local supremacy of this species concerns farmers, owing to its relatively low palatability for grazing stock, and conservationists, owing to the monotonous, species‐poor landscapes that often result under Molinietum. 2. In some environmentally sensitive areas (ESAs) in England and Wales, Molinietum is believed to have ousted Callunetum in recent decades; experiments sponsored to control the species have predicated its infiltration and replacement of heather‐dominated stands. 3. Experimental control of Molinia in ESAs on Exmoor, England, was paralleled by palaeoecological studies to verify its recent rise, assess its status in moorland, and test the utility of the techniques for such research. 4. Peat profiles from two localities on Exmoor were sampled and subjected to recently developed techniques of plant macrofossil counting and to conventional pollen analysis. One locality was ‘white moor’, clearly dominated by Molinia; the other was ‘grey moor’ (an admixture of ericaceous shrubs) that had become invaded (allegedly recently) by Molinia. 5. Dating of profiles employed a range of methods, including conventional radiocarbon dating, Accelerator Mass Spectrometry (AMS) dating and the counting of spheroidal carbonaceous particles, to attempt to delimit horizons of recent peat growth. 6. The pollen and macrofossil data confirmed the recent ousting of Calluna and rise to dominance of Molinia in the grey moor, but also provided evidence of an earlier unsuspected (pre‐Callunetum) presence of Molinia. The overwhelming dominance of Molinia in the white moor was also a recent phenomenon, but was only partly at the expense of Calluna. The palaeoecological data indicated a greater antiquity and former abundance of Molinia than is often appreciated and suggested that, over the past millennium, vegetation dominance has alternated between Callunetum and grass moor containing at least some Molinia, while the former Calluna‐dominated grey moor itself developed originally from grass moor. 7. These findings have implications for conservation management and for restoration targets in ‘degraded’ moorland. Similar palaeoecological studies have since been adopted in Wales, directly to inform conservation and management policy.
Factors associated with wolverine Gulo gulo predation on domestic sheep
Authors: Landa A. , Gudvangen K. , Swenson J.E. , Røskaft E. 
Published: March 2003

Summary 1. Following a long history of eradication campaigns against predators, wolverine Gulo gulo distribution and numbers became critically low in Norway in the 1960s. Consequently, wolverines were protected by law during the 1970s and 1980s. This led to an increase in wolverine numbers and re‐establishment in some formerly occupied habitats, resulting in increased depredation on domestic reindeer Rangifer tarandus and sheep Ovis aries. Wolverine control and licensed hunting have been used increasingly as tools to reduce the depredation since protection was introduced. However, the factors influencing the level of this depredation have not been studied. We therefore examined losses of domestic sheep grazing unattended on upland summer ranges in the Snøhetta plateau of south central Norway during 1979–94, in relation to wolverine population numbers, reproduction and control measures. This area was recently re‐occupied by wolverines and reproduction has been recorded regularly from the beginning of the study period. 2. The number of ewes and lambs recorded in organized grazing areas increased more than fivefold during the period, and losses increased proportionally with sheep numbers. The differences in losses among municipalities and grazing co‐operatives were probably related to sheep breeds and local variation in wolverine density. 3. The heavy Dala sheep breed was most at risk, whereas losses from the lighter Norwegian short‐tailed and Norwegian fur‐bearing breeds were lower than expected. 4. Killing of wolverines led to fewer lambs being lost in the same year that the wolverine killing took place, but the effect quickly declined, implying a rapid re‐establishment of wolverines in the local area. 5. Lambs were more vulnerable to wolverine predation than ewes, and losses were higher in wolverine cub‐rearing areas than in the area as a whole. 6. We conclude that: (i) control programmes for wolverines, as practised today, will have little long‐term effect in reducing sheep losses, unless wolverines are eradicated or severely reduced in numbers; (ii) the introduction of more agile sheep breeds will probably reduce losses; (iii) in areas where wolverine control to protect sheep is a threat towards wolverine conservation, the present sheep husbandry system of grazing unguarded sheep in the mountains should be replaced by alternative forms that provide the sheep with more protection. This is particularly important in wolverine denning areas.
Colobus monkeys and coconuts: a study of perceived human–wildlife conflicts
Authors: Siex Kirstin S. , Struhsaker Thomas T. 
Published: March 2003

Summary 1. Approximately half of the remaining Zanzibar red colobus Procolobus kirkii, one of Africa's most endangered primates, reside permanently outside protected areas, many within agricultural areas. Consequently, conservation of this endangered species is strongly dependent on the development of effective management plans that address the potential human–wildlife conflicts in these agricultural areas. 2. There are a growing number of complaints about red colobus consumption of coconuts in the agricultural areas and requests by local farmers for compensation and/or removal of the colobus. Prior to taking actions that would hinder the conservation of this highly endangered species, it is necessary to quantify and compare the actual impact of the colobus on coconut harvest with that perceived by the farmers. 3. In this study we monitored five experimental and two control plots to quantify the potential impact of red colobus on coconut crops and to assess the ecological variables that may influence this impact. 4. We found that red colobus consumption of coconuts was highest in areas of high red colobus density and low availability of alternative red colobus food resources. Despite these correlations, red colobus feeding on immature coconuts did not appear to limit coconut harvest. On the contrary, red colobus consumption of coconuts was found to be positively correlated with harvest. This correlation is probably due to a pruning effect. 5. Based upon our findings that red colobus are having no significant negative impact on coconut harvest and are actually a source of tourist revenue to the region, we recommend no action be taken to remove colobus from the agricultural areas. 6. This study illustrates the importance of scientific documentation of perceived human–wildlife conflicts.
Assessing the completeness of bat biodiversity inventories using species accumulation curves
Authors: Moreno Claudia E. , Halffter Gonzalo 
Published: March 2003

Summary 1. In this study we used species accumulation models to solve one of the most serious problems encountered when comparing species richness between different communities. The problem is how to compare data among inventories in which different methodologies or measures of sampling effort have been employed. The methods used here for bats may be applied to any other biological group. We fit two asymptotic models to species accumulation curves for bat inventories to evaluate local or within‐community diversity (alpha) and landscape diversity (gamma) in central Veracruz, Mexico. 2. Species accumulation models allow us to: (i) measure within‐inventory efficacy and completeness; (ii) obtain an estimate of species richness that is based on a standardized measure of sampling effort, which makes valid comparisons between inventories possible; and (iii) estimate the minimum sampling effort required to reach a satisfactory level of completeness. 3. The applied models fit well in all cases (r2 >  0·95). The linear dependence model predicted lower asymptotes and the Clench model predicted higher asymptotes than the observed species richness. These models are useful as predictors representing the lower and upper limits between which the true species richness value should lie. 4. Alpha diversity for bats in all vegetation communities (11–18 species) was lower than the gamma diversity (20 species), suggesting that species richness and the sampling effort required are related to environmental heterogeneity. 5. We propose that 90% of the total fauna predicted by either of the models is an acceptable standardized value for comparing species richness between communities. 6. We assessed the within‐inventory completeness as the proportion of the models’ asymptote, where 90% is the desired minimum level of completeness. Except in palm stands, all bat inventories had an acceptable level of completeness, at least for the linear dependence model. 7. For conditions similar to those of our study area, the minimum effort required to obtain a satisfactory level of completeness is 5–18 nights for plant communities and 18 nights for more heterogeneous landscapes. 8. We make recommendations for improving the efficacy and completeness of bat surveys based on the application of species accumulation models.
Abundance–occupancy relationships
Authors: Gaston Kevin J. , Blackburn Tim M. , Greenwood Jeremy J.D. , Gregory Richard D. , Quinn Rachel M. , Lawton John H. 
Published: March 2003

1. The abundance and distribution of species tend to be linked, such that species declining in abundance often tend also to show declines in the number of sites they occupy, while species increasing in abundance tend also to be increasing in occupancy. Therefore, intraspecific abundance–occupancy relationships are commonly positive.2. The intraspecific pattern is mirrored by more general positive interspecific abundance–occupancy relationships: widespread species tend to be abundant, and narrowly distributed species rare.3. Here, we review recent research on these patterns based on the flora and fauna of the British Isles. We assess their generality, describe what is currently known about their structure, and summarize the results of tests of the several hypotheses proposed to explain their existence.4. The positive form generally exhibited by abundance–occupancy relationships, intraspecific or interspecific, has consequences for several areas of applied ecology, including conservation, harvesting, biological invasions and biodiversity inventorying. These implications are discussed briefly.
Lamb predation and fox control in south‐eastern Australia
Authors: Greentree Carolyn , Saunders Glen , Mcleod Lynette , Hone Jim 
Published: March 2003

Summary 1.  Wild predators sometimes kill livestock. In Australia the red fox kills lambs, but there are limited experimental data to demonstrate the effects of controlling foxes on the predation level. 2.  Using a balanced experimental design over 2 years, we investigated the effects of three levels of fox control, using poisoning with sodium monofluoroacetate (compound 1080), on lamb production, lamb predation and fox abundance in south‐eastern Australia. 3.
There was no effect of fox control on lamb production. Fox predation was the probable cause of lamb death for a minimum of 0·8% and a maximum of 5·3% of 1321 lamb carcasses. Fox control significantly (P < 0·05) reduced the minimum percentage of lamb carcasses classified as killed by foxes from 1·50% (no fox control) to 0·90% (fox control once per year) or 0·25% (fox control three times per year). Fox control also significantly (P < 0·005) reduced the maximum percentage of lamb carcasses classified as killed by foxes from 10·25% (no fox control) to 6·50% (fox control once per year) or 3·75% (fox control three times per year). Poisoning did not affect fox abundance in spring. 4.  We estimated the number of treatment replicates needed to detect an effect of predator control on the number of lambs successfully reared to lamb marking (10 weeks old). The estimated numbers were high if predation effects were small. It is recommended that the effects of fox control should be evaluated carefully to determine if the present results are widespread, as some fox control may be wasted. 5.  The general effects of predator control on livestock predation requires more experimental investigation and economic evaluation. However, field experiments of sufficient power to detect effects will present considerable challenge.