bluuebunny/crossref_metadata_2025_split huggingface dataset:
The benefits of extensive agriculture to birds: the case of the little bustard
Authors: Wolff Axel , Paul Jean‐Philippe , Martin Jean‐Louis , Bretagnolle Vincent 
Published: March 2003

Summary

The little bustard Tetrax tetrax is among many birds thought to be declining because of agricultural intensification in western Europe. In contrast with the situation elsewhere, bustard numbers have greatly increased during the last 50 years in the Crau, southern France, as agriculture has been developing. We wished to ascertain which features of agricultural development might have supported this population increase.
Using data on habitat‐specific densities obtained by surveys of the Crau in 1998 and 1999, we assessed how breeding male little bustards used habitats representing various levels of agricultural intensification. We also documented historical changes in bustard numbers and agricultural trends in the Crau, comparing them with present patterns of habitat use, to determine how changes in farmed landscapes may have driven population trends.
Male bustards used natural steppe and extensive agricultural habitats (fallow, grazed crops, legume crops), whereas more intensive agricultural habitats (hay‐meadows, grain crops) were little used. Mean densities on extensive agricultural habitats were always high, but densities on steppe varied with landscape composition: densities were low where steppe was dominant in the landscape, but high where steppe and extensive agriculture were mixed.
Available literature showed that little bustards settled in the Crau around 1950, after 40% of the original steppe had been converted into arable land. We estimate a current population of 473–539 breeding males. Only 17% of the original steppe remains, but extensive agricultural habitats still represent 30% of arable land.
Both historical data and present habitat use suggest that little bustard population trends in the Crau are driven by the development of extensive agriculture. Extensive agricultural habitats may provide little bustards with resources unavailable or scarce in natural steppe. Severe declines in little bustard numbers observed elsewhere could be reversed within a few decades by restoring extensive agricultural habitats. The potential impact of current European agricultural policies is discussed, with special reference to agri‐environmental measures and set‐aside policy.
This work provides an example of an avian species that benefits from cultivated landscapes, providing that they are extensive rather than intensive. We propose a simple conceptual model to illustrate how little bustards, and possibly grassland birds in general, might respond where natural habitats are modified along orthogonal axes representing cultivation and agricultural intensification.
Dispersal and survival of juvenile feral ferrets Mustela furo in New Zealand
Authors: Byrom Andrea E. 
Published: March 2003

Summary

Introduced feral ferrets Mustela furo are a significant pest of both conservation and economic importance in New Zealand. Ferrets prey on indigenous wildlife and they also carry bovine tuberculosis (TB), a disease which may threaten New Zealand's international beef, dairy and venison markets.
Very little is known about the role of dispersal and survival of juvenile ferrets in the recovery of ferret populations after control operations, and how these parameters might affect ferret impacts on native wildlife and their role in the spread of TB.
Fifty‐two juvenile ferrets were radio‐collared at emergence from their natal dens on six study sites during 2 years, 1997–98 and 1998–99. On three sites, most introduced mammalian predators (including ferrets) had been removed by kill‐trapping from October to January to protect critical bird nesting areas. Three sites were left as non‐removal sites. Dispersal and survival of juvenile ferrets was therefore measured at low and normal ferret densities.
Survival of juvenile ferrets showed a strong density‐dependent response to predator removal. In year 1, survival of juvenile ferrets from emergence to the end of the dispersal period (about 4 months) was 86% (95% confidence limits 63–100%) on removal sites, whereas survival on non‐removal sites was 19% (0–38%). In year 2, survival was 100% on removal sites compared with 71% (45–97%) on non‐removal sites. Dispersal of juvenile ferrets was not related to population density at source.
A frequency distribution of dispersal distances of juvenile ferrets showed a typical negative‐exponential pattern. The median dispersal distance of juvenile ferrets was 5·0 km (range 0·5–45·0 km). There was no apparent sex bias in survival, dispersal distances or timing of dispersal in either season.
Density‐dependent survival of juvenile ferrets should be a key parameter of interest in determining frequency and seasonal timing of ferret control. Ferret control to conserve native wildlife and minimize TB spread should be carried out in late autumn after dispersal, to provide a longer lag time before juveniles reinvade an area.
This study fills a critical gap in the understanding of introduced mustelids in island systems such as New Zealand. It has direct implications for management of this important introduced predator, and it augments literature on dispersal and survival of mammalian carnivores.
Modelling disease spread in a novel host: rabies in the European badger Meles meles
Authors: Smith G. C. , Wilkinson D. 
Published: March 2003

Summary

Although the red fox Vulpes vulpes is the main reservoir of rabies in Europe, badger Meles meles populations are known to be drastically affected. Models of badger population dynamics are combined with a fox/rabies model to examine the possibility of rabies spread in high‐density badger populations, such as those found in the United Kingdom (UK).
Although some data exist on rabies epizootiology in the badger, there are no data on badger‐to‐badger contact rates (either healthy or diseased animals). As a starting point consensus expert opinion was used to devise contact probabilities, and the model was found to be insensitive to reasonable variation in these rates for the density of badgers at which these estimates were made.
Density‐dependent (but not density‐independent) contact probabilities simulated short chains of infections that may occur in continental Europe at low badger densities, and simulated true epizootics at higher densities.
Another possible reason for these short chains of infections in continental Europe is a very high level of fragmentation between social groups.
Given the high level of territorial contiguity and possible contact rates found in some parts of the UK, the model suggests that rabies is capable of spreading within the UK badger population, and a provisional map showing the likelihood of an epizootic is presented.
Nicotine‐like effects of cotinine on protein kinase C activity and noradrenaline release in bovine adrenal chromaffin cells
Authors: Vainio P. J. , Viluksela M. , Tuominen R. K. 
Published: March 2003

1 We studied the effect of cotinine, a slowly eliminated metabolite of nicotine, on protein kinase C (PKC) distribution and noradrenaline release in primary cultured bovine adrenal chromaffin cells. Changes in PKC activity were detected by [3H]‐phorbol‐12,13‐dibutyrate binding, histone phosphorylation assay and by Western blot. 2 Cotinine (10–32 mm) increased phorbol binding to chromaffin cells in response to 10 min but not to 24 h exposure. The increased binding was reversed by a nicotinic antagonist hexamethonium (10 μm). 3 Cotinine (10 mm, 30 min) also increased membrane‐associated PKC activity and membrane‐associated PKC α and ε immunoreactivity. 4 Cotinine (0.1–32 mm for 10 s to 20 min) dose‐ and time‐dependently increased the release of preloaded [3H]‐noradrenaline from the cultured cells. The release increased with increasing duration of the contact period. In treatments lasting 1 min or longer, a peak effect was followed by a reduced response at higher concentrations. 5 We confirm the earlier findings that cotinine is biologically active, and conclude that its effects are at least partly mediated via nicotinic cholinergic receptors and through PKC.
Effect of early stage of experimental diabetes on vascular functions in isolated perfused kidneys
Authors: García V. M. C. , Ochoa J. E. , Elías M. M. 
Published: March 2003

1 The present study investigates the renal vascular responsiveness to vasoactive agents in diabetic rats which present an early stage of renal failure. 2 Adult male Wistar rats were administered alloxan (150 mg kg–1, s.c.). Seven days later the right kidneys were isolated and perfused. Renal perfusion pressure was measured continuously. Concentration‐response curves were plotted for noradrenaline (NA), sodium nitroprusside (SNP) and carbachol. 3 In basal conditions, kidneys from diabetic rats presented a decreased vascular resistance compared with those from control rats. 4 The vasoconstrictor response to NA showed decreased EC50 values in preparations from diabetic rats compared with control ones (EC50 nmols, control: 2.03 ± 0.44, n = 8; diabetic: 0.84 ± 0.18, n = 6, P < 0.05). This enhanced sensitivity to NA could be in line with the decreased glomerular filtration rate and cortical renal plasma flow previously described in vivo in our laboratory (
Garcia et al. 1998
) . Vasoconstrictor responses to phenylephrine were not however, different between diabetic and control rat kidneys. This suggests that the increased sensitivity to NA was due to impaired neuronal uptake since phenylephrine is not a substrate for neuronal uptake. 5 After precontraction with phenylephrine, both endothelium‐dependent (carbachol) and endothelium independent (SNP) vasodilator agents caused similar response in the preparations taken from the two groups of animals. So, the enhanced sensitivity to NA is not associated with a deficient dilator responsiveness of the renal vasculature. 6 The vasodilator response to carbachol was the same in absence or presence of
l‐arginine in the perfusate, suggesting no alteration in its availability at this stage of diabetes. 7 Diabetic animals showed increased plasma level of fructosamine and glycosylated haemoglobin (Hb A1c), indicating the presence of early glycated products at this stage of diabetes, which could be involved in a possible structural alteration of the vessels.
Effects of propranolol and L‐NAME on β‐adrenoceptor‐mediated relaxation in rat carotid artery
Authors: MacDonald A. , McLean M. , MacAulay L. , Shaw A. M. 
Published: March 2003

1 The properties of β‐adrenoceptors mediating vascular relaxation in rat isolated carotid artery were investigated. Ring segments of arteries were preconstricted with the thromboxane A2 receptor agonist U‐46619 and relaxation to β‐adrenoceptor agonists determined. 2 Isoprenaline produced a concentration‐dependent relaxation of U‐44619‐constricted arteries. The concentration‐response curve (CRC) to isoprenaline was shifted to the right by propranolol (1 μm) although the shift was less (105 fold; pA2, 8.02) than would be expected for an effect of isoprenaline at classical β‐adrenoceptors (300–1000 fold; pA2, 8.5–9). L‐NAME (100 μm) significantly reduced responses to isoprenaline, lowering the slope of the CRC and reducing the maximum response. 3 The selective β3‐adrenoceptor agonists, BRL 37344 and ZD2079, also produced concentration‐dependent relaxation of the arteries. L‐NAME (100 μm) shifted the BRL 37344 CRC to the right 15 fold with no reduction in the slope or maximum response. L‐NAME (100 μm) had no significant effect on the ZD2079 CRC. 4 In conclusion, relaxation to isoprenaline in rat carotid artery is inhibited by propranolol in a manner suggesting a mixed population of classical (β1‐/β2‐) and atypical (β3‐) adrenoceptors. The presence of β3‐adrenoceptors was confirmed by the relaxant effects of the selective β3‐adrenoceptor agonists BRL 37344 and ZD2079. L‐NAME attenuated responses to both isoprenaline and the β3‐adrenoceptor agonist BRL 37344, suggesting a role for endothelial release of nitric oxide in β‐adrenoceptor mediated relaxation. However, the relaxant effect of BRL 37344 was attenuated by L‐NAME to a lesser extent than that of isoprenaline. In addition, L‐NAME had no effect on relaxation induced by ZD2079. These results suggest that there may be a differential contribution of endothelium to classical β‐and β3‐adrenoceptor‐mediated effects, with endothelium contributing less to β3‐adrenoceptor‐mediated relaxation.
Wall tension and contraction of the aorta in 6‐month‐old spontaneously hypertensive rats
Authors: Nunes J. P. L. , Guimarães Serafim 
Published: March 2003

1 The present study aimed at comparing the influence of passive tension on the effect exerted by noradrenaline on the thoracic aorta of 6‐month‐old Wistar and spontaneously hypertensive rats (SHR). 2 Concentration–response curves to noradrenaline were obtained in aorta rings, at two levels of passive tension: 3 and 0.5 g. 3 The maximal responses (in percentage of the maximal response to noradrenaline obtained in the beginning of the experiment at a tension of 2 g) were significantly larger (P < 0.05) at 3 g than at 0.5 g in both kinds of rats: 171 versus 69%, respectively, for SHR; 139 versus 76%, respectively, for Wistar rats. 4 When expressed as mg of active tension per mg of tissue, the maximal contraction at both 3 and 0.5 g was smaller in SHR than in Wistar rats (at 3 g: 64.6 ± 6.7, n=6 versus 122.3 ± 19.1, n=8, respectively, P < 0.05; at 0.5 g: 24.0 ± 1.0, n=6 versus 49.0 ± 5.9, n=8, respectively, P < 0.05). 5 Maximal responses to noradrenaline were markedly decreased by cytochalasin B (50 μM) (to 15.2 ± 6.0%, n=6, at 3 g and 2.8 ± 1.9%, n=6, at 0.5 g in SHR; to 11.8 ± 2.3%, n=4, at 3 g and 4.3 ± 1.3%, n=4, at 0.5 g in Wistar rats). Cytochalasin B at a lower concentration (4 μM) produced a less marked decrease in responses to noradrenaline in both strains of rats. The presence of cardiovascular structural changes in SHR was confirmed by the fact that the heart weight (mg):body weight (g) was higher in SHR (3.37 ± 0.06, n=10) than in Wistar rats (2.40 ± 0.12, n=11) (P < 0.05). 6 It is concluded that in 6‐month‐old SHR the contractile capacity of the aortic tissue is reduced. However, the differential sensitivity of aortic smooth muscle at the two different levels of tension remains present. This difference may depend on filament interaction. Contractions to noradrenaline in the rat aorta are highly dependent on actin polymerization.
Stand structure of the emergent conifer Agathis ovata in forest and maquis, Province Sud, New Caledonia
Authors: Enright N. J. , Goldblum D. 
Published: March 2003

Abstract. The size structure of the endemic New Caledonian conifer Agathis ovata is reported for sample stands in forest and maquis from three areas on ultramafic substrates in the south of the main island (Grand Terre). In closed forest Agathis ovata is typically represented by a low density of emergent adult trees with only limited evidence of seedling recruitment. In maquis, Agathis ovata is represented by individuals of all sizes, with seedlings and saplings abundant in most sample stands. Preliminary evidence from tree‐ring studies indicates that rings may be annual. Estimated diameter growth rate is about 2 mm y−1 for trees ≥ 10 cm d.b.h., and ring counts suggest tree ages of up to 400 years in maquis and 500 years in forest.Agathis ovata, and three other members of the Araucariaceae found in New Caledonia (Araucaria laubenfelsii, A. montana and A. rulei), are the only tree species which regularly occur scattered in maquis in this way, creating an unusual structural assemblage. No angiosperm tree species show this behaviour. The circumstances under which the Agathis ovata– maquis stands arise and are maintained are the subject of further investigation. Preliminary evidence for tree ages indicates that these stands predate European arrival in New Caledonia and so are not the result of recent increases in the frequency and intensity of human disturbances. The presence of fire scars on many individuals, and location of most stands on slopes and spurs with outcropping laterite (cuirasse), suggests that this assemblage may owe its existence to the interplay of fire regime, topography and rockiness, and a resistance to fire in Agathis ovata which increases with plant size and age.
Biodiversity on oceanic islands:a palaeoecological assessment
Authors: Sadler Jon P. 
Published: March 2003

SummaryIslands are bounded ecosystems and serve as excellent laboratories for assessing changes in Biodiversity. Some oceanic islands, such as Madagascar, Bermuda and notably the islands in the Pacific (e.g. Hawaii), are home to unique forms of endemic plants and animals that have evolved in isolation over millions of years. The palaeoecological record indicates that such islands are characterized by waves of extinctions concomitant with colonization by humans. By way of contrast, the biota of the islands of the north Atlantic (Greenland, Iceland and Faroe) do not follow the expected pattern and the few extinctions recorded are very localized. This is not a result of the scale of human impact, which is as great as on other islands, but relates to the virtual lack of endemics. The dearth of endemic forms and the disharmonic nature of these island communities indicates a youthful biota and the operation of severe filters and sweepstakes during colonisation over the last 10,000 years. This paper draws upon an extensive invertebrate fossil record to contrast and examine these spatial and temporal patterns in island Biodiversity.
Do local abundances of British birds change with proximity to range edge?
Authors: Blackburn Tim M. , Gaston Kevin. J. , Quinn Rachel M. , Gregory Richard D. 
Published: March 2003

Summary Aim Species generally vary in the density they attain at different sites, prompting the question of whether this variation is systematic across their range. We investigate this question using data on the abundance and distribution of thirty‐two species of passerine birds across Britain derived from censuses organized by the British Trust for Ornithology. Methods Analysis is complicated by the issue of quantifying the distance of any particular census location from the edge of the range of a species when the study area encompasses only part of its entire distribution. No measure of this quantity is a priori the correct one, and so we use a variety of different measures which make differing assumptions about how abundances might be structured across species ranges. Results None of the measures used reveal any consistent relationships between the density attained by species at census sites and the spatial positions of those sites. Only thirteen species show significant relationships with any of the measures, and no more than seven species with any single measure. Main conclusion In summary, there is no convincing evidence that passerine bird densities are usually lower towards range edges in Britain. We discuss possible reasons for these findings.
Molecular genetic evidence for the post‐Pleistocene divergence of populations of the arctic‐alpine ground beetle Amara alpina (Paykull) (Coleoptera: Carabidae)
Authors: Reiss Rebecca A. , Ashworth Allan C. , Schwert Donald P. 
Published: March 2003

Summary Aim This study examines the hypothesis that the biogeographic history of a species is reflected in the distribution of molecular genetic diversity and the phylogenies of extant populations. Location Populations of arctic‐alpine ground beetle Amara alpina were analysed from Beringia (Alaska and northernmost British Columbia), the Hudson Bay region, the northern Appalachian Mountains, and the central Rocky Mountains of North America. Methods Mitochondrial restriction site variation of specimens from twenty‐two populations were assayed by using radioactively labelled mtDNA to probe Southern membranes containing restriction enzyme digested total DNA. Restriction sites were mapped and genetic distances were calculated by pairwise comparison of presence and absence of restriction sites. Genetic distances were used in a molecular analysis of variance and to construct a minimal spanning tree. Parsimony methods were used to investigate the phylogenetic relationships between the haplotypes. These results were compared to an existing model for postglacial dispersal based on fossil and modern occurrences of arctic‐alpine beetles. Results Among the twenty‐two populations, fifteen haplotypes were detected. Genetic variation within each of the four regions corresponded to that expected from the palaeontologically based model. Beringian populations were the most genetically diverse. In contrast, no restriction site variation was observed in populations from the Hudson Bay region. Intermediate amounts of variation were observed in alpine populations of the Rocky and Appalachian Mountains. Maximum parsimony and cluster analysis provide evidence that at least two ancestral haplotypes existed in the Southern refugium from which the Rocky and the Appalachian Mountains populations were founded. Main conclusions The genetic results are generally consistent with the palaeontologically based model. The diversity of Beringian populations is consistent with this region having been continuously inhabited by Amara alpina throughout the Pleistocene. The Hudson Bay region was not deglaciated until about 6000 years, and its populations have no restriction site variation. The molecular genetic data support the interpretation that the Hudson Bay region was colonized from Beringia based on the occurrence of the same haplotype in both regions.
Urban plant ecology patterns and processes: a case study of the flora of the City of Plymouth, Devon, U. K.
Authors: Kent M. , Stevens R. A. , Zhang L. 
Published: March 2003

Summary AimUsing a large database that has been created over the past 5 years with the RECORDER package, presence/absence data for 829 species of vascular plants in the 103 1‐km2 squares that cover the city of Plymouth (pop. 243,373) have been analysed by two‐way indicator species analysis (TWINSPAN) and canonical correspondence analysis (CCA) to establish the major species assemblages and to examine their spatial distribution across the city in relation to variation in land use. LocationThe City of Plymouth. MethodsNine groupings of squares emerged and their distribution was mapped across the city. Interpretation of those groups and their variation in relation to the land use ordination axes showed that TWINSPAN groups lying along the first axis of variation correlated floristic variation with the process of urban development and the historical evolution of urban structure. The second axis appeared to be related to particular remnant semi‐natural habitats within the city that could be regarded as ‘hot‐spots’ for survival of many plant species. Species were categorized into four types on the basis of their recency and mode of arrival in the city and by using the historical flora of Plymouth produced by T. R. Archer‐Briggs in 1880. Variations in the sources of species in relation to the TWINSPAN classification groups were then examined. A second ordination was also computed; this time with geological, altitudinal and distance variables. TWINSPAN groups were then superimposed on the ordinations using polygons to assist with biogeographical interpretation. Results and conclusions The results of both the multivariate analyses and distribution of species by source are then discussed in the context of previous research into urban plant ecology, particularly in Central Europe. The problems of inferring process from pattern in this meso‐scale study are reviewed and suggestions are made for further research into urban ecology and biogeography in the city.