bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships between livestock management and the ecological condition of riparian habitats along an Australian floodplain river
Authors: Amy Jansen , Robertson Alistar I.
Published: March 2003

Grazing by introduced ungulate livestock is a major form of land use over large parts of Australia. Due to the tendency of stock to concentrate around water, riparian zones and wetlands are heavily impacted by grazing. However, little is known about how effects on riparian habitats vary spatially and with management regimes. We investigated how livestock affected riparian habitats on the Murrumbidgee River in south‐eastern Australia.

A rapid appraisal index of the ecological condition of floodplain riparian habitats was developed. This measured habitat continuity and extent, vegetation cover, bank stability, soil structure, quantity of fallen debris, dominance of natives vs. exotics, and the presence of indicative species. The method could be readily adapted for use on other floodplain rivers with extensive riparian habitats.

Riparian condition was scored at 138 sites along 620 km of the Murrumbidgee River on private properties (n = 77), in State Forests (n = 27) and on Crown Land (n = 34). Riparian condition declined significantly with increasing grazing intensity and also with distance upstream in the upper half of the floodplain.

Stocking rate, distance upstream, relative periods of paddock rest and grazing, proportion of bank accessible to stock, and the presence of off‐river water in the paddock, accounted for 76% of the variance in riparian condition.

Most riparian habitats on the Murrumbidgee River and other rivers in the Murray‐Darling Basin are privately owned. Thus exclusion of the grazing industry from the riparian zone is not practical. However, lowered stocking rates, particularly in the upper parts of the catchment, resting of paddocks to allow recovery from grazing, and the provision of off‐river watering points could all be used to improve riparian habitats.

Exotic plants are ubiquitous, occurring even where grazing has been excluded for many years. Thus restoration of riparian habitats will require weed removal even in areas not used by livestock.
Identifying rice fields at risk from damage by the greater flamingo
Authors: Tourenq Christophe , Aulagnier Stéphane , Durieux Laurent , Lek Sovan , Mesléard François , Johnson Alan , Martin Jean‐Louis
Published: March 2003

Since the early 1980s, greater flamingos Phoenicopterus ruber roseus have been reported to cause damage to the rice fields of the Camargue, south‐eastern France.

 We tested whether some rice fields had landscape features that were more attractive to flamingos than others, using data from the period 1993–97 and from 1978 different paddies. Discriminant function analysis (DFA), logistic regression (LR) and artificial neural networks (ANN) were used to identify the environmental variables best explaining flamingo incursions.

 The most accurate models (LR) gave 75% prediction success and used as predictors the surface area of rice fields, the presence of contiguous damaged fields, the presence of wooded margins and the distance to natural marshes.

 Our study suggests that it is possible to identify accurately fields at risk from damage in order to concentrate scaring methods. We also suggest that planting hedges should be promoted, and wood cutting discouraged, in high‐risk areas. Following our study a programme of planting of hedges by the Natural Regional Park of the Camargue started at the beginning of 2000.

 Our work reveals how presence–absence modelling can have clear applications in managing important species that sometimes cause negative impacts locally.
Refuge habitats modify impact of insecticide disturbance on carabid beetle communities
Authors: Lee Jana C. , Menalled Fabián D. , Landis Douglas A.
Published: March 2003

Carabid beetles are polyphagous predators that can act as biological control agents of insect pests and weeds. While current agricultural practices often create a harsh environment, habitat management such as the establishment of within‐field refuges has been proposed to enhance carabid beetle abundance and impact. We examined the joint effects of refuge habitats and insecticide application on carabid activity density (parameter of population density and relative activity) and species composition in a cornfield.

Our 2‐year study comprised four treatments: (i) −refuge/−insecticide; (ii) +refuge/−insecticide; (iii) −refuge/+insecticide; (iv) +refuge/+insecticide. Refuge strips consisted of grasses, legumes and perennial flowering plants. ‘−Refuge’ strips were planted with corn and not treated with insecticide.

Before planting and insecticide application, carabid activity density in the crop areas was similar across all treatments. Insecticide application immediately reduced carabid activity density and altered community composition in the crop area.

Refuge strips had significantly higher activity density of beetles than −refuge strips before planting and during the summer.

During summer, as new carabids emerged and insecticide toxicity declined, the presence of refuge strips influenced carabids in the adjacent crop area. Carabid activity density within crop areas previously treated with insecticide was significantly higher when adjacent to refuge strips. Also, carabid communities within insecticide‐treated crop areas were affected by the presence or absence of a refuge strip.

The presence of refuge strips did not consistently augment carabid numbers in crop areas where insecticide was not applied. One explanation may be that insecticides decreased the quality of crop habitat to carabids by depletion of prey and direct mortality. However, subsequent rebounds in prey density and the absence of competing predators may make these areas relatively more attractive than unperturbed crop habitats to carabid colonization from refuges.

This study demonstrates that refuges may buffer the negative consequences of insecticide application on carabids in adjacent fields. Diversifying agro‐ecosystems with refuge habitats may be a viable strategy for maintaining carabid populations in disturbed agricultural landscapes to keep pests below outbreak levels.
Validation of a spatial simulation model of a spreading alien plant population
Authors: Higgins Steven I. , Richardson David M. , Cowling Richard M.
Published: March 2003

Process‐based models, and spatially explicit models in particular, will play an important role in predicting the impacts of future environmental change. Enthusiasm for the rich potential of these models, however, is tempered by the realization that their parameterization is often challenging and time consuming. Moreover, these models are seldom validated; this makes their predictive value in applied contexts uncertain.

In this paper we describe the process of parameterizing and validating a spatial demographic model of a spreading alien plant population. The model, a spatially explicit individual‐based simulation, has modest data requirements (for a spatial simulation model) in that it concentrates on simulating recruitment, dispersal, mortality and disturbance and ignores the environmental and biotic heterogeneity of the receiving environment.

We tested the model using the invasion ofAcacia cyclopsandPinus pinasterinto fynbos, the mediterranean shrublands of South Africa, as a case study. Dispersal, recruitment and mortality data were collected for each species at six different sites. Aerial photographs from six independent sites (two sites forA. cyclopsand four sites forP. pinaster)were used to reconstruct the invasion histories of the two species between 1938 and 1989. Demographic data were used to parameterize the model, and the 1938 distribution of alien plants, derived from aerial photography, was used to initialize the model.

The empirically estimated indices of rate and pattern of invasion fell within the range of model predictions made at all six sites studied. The indices of rate and pattern of invasion predicted by the model did not differ significantly from the empirically estimated indices for 76% of the model data comparisons made. These analyses suggested that the model predictions are good, given the variance in parameter estimates.

The proportion of grid locations where the model correctly predicted alien plant distribution was typically above 0·75 and always above 0·5 for both species. A permutation test showed that locations of invasive plants predicted by the model were significantly better than random forP. pinaster, but not always forA. cyclops;this may be becauseA. cyclopsis bird dispersed, and its dispersal may be biased towards perch sites, whereasP. pinasteris wind dispersed.

We conclude that, although spatial simulation models are often more difficult to parameterize and validate than statistical or analytical models, there are situations where such effort is warranted. In this case the validation process provides confidence to use the model as a tool for planning the control of invasive plants. In a more general sense we believe that the approach outlined here could be used for model parameterization and validation in situations where spatial simulation models seem appropriate.
Effects of ultraviolet‐B radiation and pH on early development of the moor frogRana arvalis
Authors: Pahkala Maarit , Laurila Anssi , Björn Lars Olof , Merilä Juha
Published: March 2003

Although the potential negative effects of increased ultraviolet‐B (UV‐B) radiation on early life stages of aquatic organisms are widely recognized, possible synergistic effects with other stressors have seldom been studied outside the laboratory. We investigated the effects of UV‐B radiation and pH on hatchability and early development of moor frogRana arvaliseggs in the field and in laboratory experiments conducted during April 1998 and April 2000 in central Sweden.

 In the field experiments, no evidence was found for reduced hatchability or increased frequency of developmental anomalies of embryos exposed to ambient levels of UV‐B compared with embryos shielded from UV‐B radiation.

 Hatchlings shielded from ambient UV‐B radiation did not grow larger than their exposed full‐sibs, giving no support to the hypotheses that (i) the repair of cellular UV‐B damage might be energetically costly nor (ii) that UV‐B‐induced photoproducts directly reduce growth.

 Although low pH (5·0) reduced hatchability, increased frequency of developmental anomalies and reduced early embryonic growth inR. arvalis, there was no evidence for synergistic effects of pH and UV‐B on any of these traits.

 The lack of UV‐B radiation effects on the development ofR. arvalisembryos cannot be ascribed to relatively low effective daily doses of radiation (c. 0·43 kJ m−2) during the field experiments, as in the laboratory even higher doses at UV‐B 1·25 kJ m−2and 1·58 kJ m−2(all DNA weighed) had no negative effects.

 These results suggest that current levels of UV‐B radiation in northern Europe are not likely to reduce fitness in natural populations of the moor frog, even in areas already stressed by acidity.
Predicting shorebird mortality and population size under different regimes of shellfishery management
Authors: Stillman R. A. , Goss‐Custard J. D. , West A. D. , Durell S. E. A. Le V. Dit , McGrorty S. , Caldow R. W. G. , Norris K. J. , Johnstone I. G. , Ens B. J. , Van Der Meer J. , Triplet P.
Published: March 2003

Human interests often conflict with those of wildlife. In the coastal zone humans often exploit shellfish populations that would otherwise provide food for populations of shorebirds (Charadrii). There has been considerable debate on the consequences of shellfishing for the survival of shorebirds, and conversely the effects of shorebird predation on the shellfish stocks remaining for human exploitation. Until now, it has been difficult to determine the impact of current shellfishery practices on birds or to investigate how possible alternative policies would affect their survival and numbers.

 One long‐running contentious issue has been how to manage musselMytilus edulisand cockleCerastoderma eduleshellfisheries in a way that has least effect on a co‐dependent shorebird, the oystercatcherHaematopus ostralegus, which also consumes these shellfish. This study used a behaviour‐based model to explore the effects that the present‐day management regimes of a mussel (Exe estuary, UK) and a cockle (Burry inlet, UK) fishery have on the survival and numbers of overwintering oystercatchers. It also explored how alternative regimes might affect the birds.

 The model includes depletion and disturbance as two possibly detrimental effects of shellfishing and some of the longer‐term effects on shellfish stocks. Importantly, model birds respond to shellfishing in the same ways as real birds. They increase the time spent feeding at low tide and feed in fields and upshore areas at other times. When shellfishing removes the larger prey, birds eat more smaller prey.

 The results suggest that, currently, neither shellfishery causes oystercatcher mortality to be higher than it would otherwise be in the absence of shellfishing; at present intensities, shellfishing does not significantly affect the birds. However, they also show that changes in management practices, such as increasing fishing effort, reducing the minimum size of shellfish collected or increasing the daily quota, can greatly affect oystercatcher mortality and population size, and that the detrimental effect of shellfishing can be greatly increased by periods of cold weather or when prey are unusually scarce. By providing quantitative predictions of bird survival and numbers of a range of alternative shellfishery management regimes, the model can guide management policy in these and other estuaries.
Pollen removal and deposition by honeybee and bumblebee visitors to apple and almond flowers
Authors: Thomson James D. , Goodell Karen
Published: March 2003

To help evaluate the worth of alternative pollinators in agriculture, we present a theoretical framework for comparing the effectiveness of two or more pollinators by measuring pollen removal and deposition.

We report pollen removal and deposition data by Apis mellifera and Bombus spp. during single visits to four cultivars of apples (Golden Delicious, Starkrimson Delicious, Empire/MacIntosh and Rome) and Mission almond.

Apis and Bombus removed similar amounts of pollen from apple flowers but Bombus deposited more pollen on stigmas. Pollen‐collecting bees removed more pollen from apple anthers than nectar‐collecting bees. Apis that approached nectaries laterally deposited substantially less pollen than other visitors.

Apis and Bombus removed and deposited similar amounts of pollen on almond flowers. Apis tended to remove more during pollen‐collecting visits than nectar‐collecting visits. The type of resource sought did not significantly influence deposition.

Based on removal and deposition data, additions of Bombus may increase pollen delivery in apple orchards but reduce pollen delivery in almond orchards if Apis already serve as primary pollinators. Additional data on inter‐tree and inter‐row flights would be necessary to know how much these changes in pollen transfer might affect fertilization.

Measures of pollen‐transfer effectiveness do not provide a complete assessment of pollination value, but can serve as a general, inexpensive tool for pre‐screening possible alternative pollinators.
Are urban bird communities influenced by the bird diversity of adjacent landscapes?
Authors: Clergeau Philippe , Jokimäki Jukka , Savard Jean‐Pierre L.
Published: March 2003

The species diversity of adjacent landscapes influences the conservation or restoration of several animal groups in urban areas, but the effect on birds is unclear. To address this question, we compared bird species richness (BSR) and community composition between periurban (area surrounding the town) and urban (suburban and centre areas) landscapes across three spatial scales.

At a large biogeographical scale (temperate and boreal climatic zone), relationships between the BSR of urban areas and their surrounding landscapes were examined in a meta‐analysis of 18 published studies. In general, BSR was negatively correlated with latitude and urbanization. The BSR of suburban and centre landscapes correlated positively with the BSR of periurban landscapes. However, latitudinal effects were also involved, as BSR in urban and periurban landscapes declined as town latitude increased. Similarity indices were low (50%) between periurban and centre bird communities.

At a regional scale, we assessed winter bird data from several towns within three regions of temperate and boreal countries (western France, northern Finland and eastern Canada). The type of periurban landscape, number of inhabitants and town diameter did not affect BSR. BSR was similar between the cities of a given biogeographical area. Bird communities were more similar between similar habitat types of different cities than between different habitats of the same city.

At a local scale, we tested the influence of proximity to the periurban landscape on BSR in parks of western French towns of different size. Neither BSR nor community similarity changed in relation to the distance of the park from the periurban landscape.

Guild composition according to diet and feeding habitat did not vary between urban and periurban locations at regional or local scales.

We conclude that, at regional and local scales, urban bird communities are independent of the bird diversity of adjacent landscapes, and that local features are more important than surrounding landscapes in determining BSR. Whatever the biodiversity quality of the periurban landscape, site‐specific actions such as shrub and tree planting, water restoration and increasing vegetation diversity can change bird diversity in towns and improve the quality of human–wildlife contacts.
The verification and application of bioindicators: a case study of dung beetles in a savanna ecosystem
Authors: McGeoch Melodie A. , Van Rensburg Berndt J. , Botes Antoinette
Published: March 2003

Bioindicators of habitat quality and environmental change must be identified quantitatively and tested independently to confirm their usefulness. We used the indicator value (IndVal) method, which combines measures of habitat fidelity and specificity, to assess the indicator responses of dung beetles (Coleoptera: Scarabaeidae) in Tembe Elephant Park, South Africa. The indicator responses were verified by sampling in different areas of the Park, 2 years after the responses were originally quantified.

We postulated that terrestrial insect indicators with different combinations of habitat specificity and fidelity might fulfil different indicator roles. Indicator species with strong habitat specificity (characteristic species) are unlikely to provide information on the direction of ecological change despite high vulnerability. Rather, detector species that span a range of ecological states are likely to be better in this role. We used IndVal for selecting such detector species that indicate the direction of ecological change.

Sets of species were found to be robust bioindicators, i.e. reliably characteristic across the habitat of which they were indicative. The suite of indicators was refined by discarding those with IndVals that varied significantly across years, thus improving the confidence in the final suite of species selected. By clearly responding to a change in habitat between two ecological states, detector species provided information complementary to that provided by characteristic species.

The IndVal method enabled both the identification and testing of indicator (characteristic and detector) species. Because of its resilience to changes in abundance, IndVal is a particularly effective tool for ecological bioindication.

We conclude that both characteristic and detector species are useful bioindicators of habitat quality and conversion. We propose that bioindicators that are categorized and verified in this way will have valuable application in the monitoring of habitat integrity.
Can niche use in red and grey squirrels offer clues for their apparent coexistence?
Authors: Bryce Jenny , Johnson Paul J. , Macdonald David W.
Published: March 2003

Introduced species are, world‐wide, one of the most serious threats to biodiversity. Grey squirrels Sciurus carolinensis are one of many introduced species to have threatened a native congener; they are thought to have replaced red squirrels Sciurus vulgaris throughout much of the UK as a result of competition. The rate of competitive replacement may be influenced by habitat composition, with some red squirrel populations persisting for prolonged periods in the presence of greys in predominantly coniferous forest.

Here the similarity of red and grey squirrels’ pattern of habitat use was investigated in Craigvinean forest in Scotland, UK, a site that has experienced apparent coexistence for up to 30 years. Overlap was examined in several dimensions: spatial overlap of home ranges, dynamic association and niche overlap. Habitat selection was examined at three levels: selection of core home range areas, selection of tree species within the home range, and the characteristics of patches used intensively by each squirrel species in comparison with random locations within their home range.

Although there was overlap between red and grey squirrel ranges, there were clear differences in the macrohabitats utilized, with red squirrels selecting areas of Norway spruce Picea abies and grey squirrels selecting riparian corridors of mixed woodland for their home ranges. Within their home ranges, habitat selection by individual red and grey squirrels was similar, but again with reds selecting Norway spruce and greys selecting patches of mixed conifers and broad‐leaved trees. As no habitat variables consistently affected the microdistribution of red and grey squirrels within blocks or ‘stands’ of trees, stands that were used were thought to constitute good and relatively homogeneous habitats for squirrels of either species.

There was no evidence to suggest that red and grey squirrels avoided using the same areas at the same time, and potential niche overlap was considerable (0·77). However, partitioning of habitats may have reduced competition between red and grey squirrels and hence have contributed to red squirrel persistence at this site.

This work (i) reinforces earlier proposals that forest management offers a promising tool to assist the conservation of red squirrels; (ii) raises the issue of determining the spatial scale at which coexistence operates; and (iii) offers an illustration of how the management of invasive species can be mediated through the manipulation of niche availability.
Diversity of Burkholderia isolates from woodland rhizosphere environments
Authors: Richardson J. , Stead D.E. , Elphinstone J.G. , Coutts R.H.A.
Published: March 2003

Aims: Determination of genetic diversity among UK Burkholderia cepacia isolates from various environmental niches, principally woodland tree rhizospheres and onions. Methods and Results: Genus determination was made using polymerase chain reaction (PCR) amplification and fatty acid methyl ester profiling. Genetic diversity was investigated by repetitive sequence genetic PCR fingerprinting. Several onion isolates were similar to clinical isolates but others were diverse. Some environmental isolates were possibly synonymous with B. cepacia and B. gladioli but most from woodland rhizospheres were distinct and clustered together. The 16S rRNA genes of representatives from these clusters were PCR amplified, sequenced and phylogenetically compared with all known Burkholderia and related species. This revealed that the rhizospheric isolates had closest affinity with Burkholderia spp. with known bioremediative and biocontrol capabilities and were unrelated to taxa comprising plant or human pathogenic strains. Conclusions: All of the analyses investigated revealed that environmental and onion isolates of B. cepacia complex bacteria are genetically diverse but that woodland rhizospheric isolates are related to each other and unrelated to plant or human pathogenic strains. Significance and Impact of the Study: Woodland rhizospheric isolates of B. cepacia are potentially good candidates for use in bioremediation and biocontrol, as they appear distinct from plant or human pathogenic strains.
Culture conditions influencing phytase production ofMitsuokella jalaludinii, a new bacterial species from the rumen of cattle
Authors: Lan G.Q. , Abdullah N. , Jalaludin S. , Ho Y.W.
Published: March 2003

Aims: The effects of pH, temperature, phytate, glucose, phosphate and surfactants on the phytase production of Mitsuokella jalaludinii, a new bacterial species from the rumen of cattle, were evaluated. Method and Results: By using batch fermentation, it was found that phytase production of M. jalaludinii was induced by sodium phytate. Inclusion of glucose into rice bran–soybean milk (RB-SM) medium inhibited the phytase production. Supplementation of 0·05–0·5% of phosphate to RB-SM medium neither inhibited nor stimulated the phytase production. The optimum pH and temperature for the phytase production of M. jalaludinii were 7·02 and 39°C, respectively. Surfactants such as Tween-80 (0·5% and 1·0%) and Triton X-100 (1·0%) did not affect the phytase production. Conclusions, Significance and Impact of the Study: The study has provided important data on the culture conditions affecting phytase production of M. jalaludinii, which will facilitate future research on the optimization of fermentation processes for production of high phytase activity by M. jalaludinii.
Effect of venlafaxine hydrochloride in different preparations of isolated guinea‐pig and rat organ tissues
Authors: Velasco A. , Arruza A. , Maroto M. , Carvajal A. , Del Busto E. Fernández ,   &, Del Pozo J. García
Published: March 2003

1 A study was undertaken to know better the effects of venlafaxine hydrochloride on the responses of isolated rat vas deferens to noradrenaline and dopamine, those of isolated rat uterus to serotonin and histamine, and those of isolated guinea‐pig ileum to acetylcholine and histamine.

2 Venlafaxine hydrochloride increased the response of rat vas deferens to noradrenaline but not to dopamine. Venlafaxine did not alter the response of rat isolated uterus to serotonin. In rat uterus, venlafaxine did not modify the response to histamine but was able to increase it in guinea‐pig ileum. An anticholinergic effect was observed with the lowest concentration tested.

3 Although venlafaxine is a selective serotonine reuptake inhibitor in the central nervous system, serotonin uptake was not seen in the rat uterus. The anticholinergic effects observed in the present study might be consistent with some of the side‐effects associated with venlafaxine.
Autoregulation of neurotransmitter release at autonomic nerve terminals: a questionable theory
Authors: Kalsner S.
Published: March 2003

1 The evidence for feedback regulation of neurotransmitter release by means of autoreceptors is questioned.

2 Autoreceptor function must meet the expectations for feedback loops. However, this concordance has not been observed in most neuroeffector systems.

3 The characteristics of per pulse transmitter release with changes in the parameters of stimulation in several autonomic systems do not support the ongoing operation of negative feedback loop mediated by locally released transmitter. Also, the effects of antagonists and agonists often do not comply with feedback expectations.

4 Evidence is provided that agonists and antagonists act at different loci to achieve their inhibiting and potentiating effects on transmitter release.

5 Future efforts should be directed to exploring the mechanism(s) of antagonist action and to a system‐by‐system analysis of the evidence for and against autoreceptor operation.
Comparison of IY81149 with omeprazole in rat reflux oesophagitis
Authors: Kil B. J. , Kim I. W. , Shin C. Y. , Jeong J. H. , Jun C. H. , Lee S. M. , Kim D. Y. , Huh I. H. , Sohn U. D.
Published: March 2003

1 This study was aimed at evaluating the effects of IY81149{2‐[[(4methoxy‐3‐methyl)‐2‐pyridinyl]methylsulfinyl]‐5‐(1H‐pyrrol‐1‐yl)‐1H‐benzimidazole}, a new proton pump inhibitor, on the development of the surgically induced reflux oesophagitis, on gastric secretion and on lipid peroxidation which is a marker of oxidative stress. Omeprazole was used as a reference drug. We furthermore investigated the influence of quercetin and desferrioxamine (DFO) on the development of the surgically induced reflux oesophagitis in rats on gastric secretion and on lipid peroxidation.

2 IY81149 and omeprazole significantly prevented the development of reflux oesophagitis and gastric secretion in a dose‐dependent manner. The ED50 values of IY81149 for inhibition of oesophagitis and volume of gastric secretion were lower than of omeprazole (5.7 vs. 14.2 μmol, 15.3 vs. 24.0 μmol, respectively). IY81149 was also more potent in the acid output inhibition with an ED50 of 6.8 μmol compared with 20.8 μmol of omeprazole.

3 Malonyldialdehyde (MDA) content, the end product of lipid peroxidation, increased significantly in the oesophageal mucosa after the induction of reflux oesophagitis. IY81149 and omeprazole significantly and dose‐dependently prevented lipid peroxidation. Quercetin (200 mg kg−1, p.o.) and DFO (800 mg kg−1, i.d.) significantly prevented the development of reflux oesophagitis and inhibited the lipid peroxidation independent of their actions on gastric secretion.

4 This result suggests that IY81149 is comparable with omeprazole in the treatment of reflux oesophagitis.
Acute renal failure in 2K2C Goldblatt hypertensive rats during antihypertensive therapy: comparison of an angiotensin AT1 receptor antagonist and clonidine analogues
Authors: Sattar M. A. , Yusof A. P. M. , Gan E. K. , Sam T. W. , Johns E. J.
Published: March 2003

1 This study compared the effect of a non‐peptide angiotensin II receptor antagonist and a series of clonidine analogues on blood pressure and renal function in a two‐kidney two‐clip Goldblatt rat model of hypertension subjected to 2 weeks of dietary sodium deprivation.

2 Animals received either vehicle, the angiotensin II antagonist, ZD7155 or structural analogues derived from clonidine (AL‐11, AL‐12 and CN‐10) at 10 mg kg−1 day−1 for 4 days.

3 All groups of rats had systolic blood pressure in the hypertensive range (160–180 mmHg). ZD7155 caused a 33‐mmHg fall in blood pressure (P < 0.05) and raised plasma urea and creatinine four‐ to six‐fold.

4 AL‐12 decreased blood pressure by 30 mmHg (P < 0.05), but had no effect on water intake, urine flow or plasma urea and creatinine. AL‐11 and CN‐10 had minimal effects on blood pressure and water intake and while CN‐10 decreased urine flow on the third treatment day, AL‐11 markedly reduced urine flow by some 70%.

5 These data show that in this sodium deficient renovascular model of hypertension, blockade of angiotensin II receptors normalizes blood pressure but causes renal failure, whereas the vasodepressor action of the clonidine analogue AL‐12 occurs without detriment to renal function. These findings imply that angiotensin II receptor antagonists could lead to renal failure if used as antihypertensive agents in renovascular hypertension whereas this would be avoided with the use of clonidine‐like analogues.
The influences of extremely low frequency magnetic fields on clonidine‐induced sleep in 2‐day‐old chicks
Authors: Min Y. S. , Jeong J. H. , Choi Y. M. , Lee B. C. , Huh I. H. , Lee S.‐Y. , Sohn U. D.
Published: March 2003

1 It has been shown that magnetic fields (MFs) affect a variety of biological effects in animal brains. There have been few experiments on the effects of MFs on sleep. Therefore, we investigated whether extremely low frequency (ELF) MFs affect the sleep induced by clonidine, a central α2‐adrenoceptor agonist. Clonidine produced dose‐related increase of the sleeping time and dose‐related decrease of the onset time in 2‐day‐old chicks.

2 Exposure of chicks to MFs (5, 10, 20 G; for 3, 6, 9, 12 h) significantly increased the clonidine‐induced sleep time as a direct function of intensity and duration of MF application. Clonidine reduced noradrenaline or tyrosine in the brain, an effect which was not further changed in animals exposed to MF.

3 To determine whether the gamma amino butyric acid A (GABAA)/benzodiazepine (BZD) receptor system is involved in the decrease in clonidine‐induced sleep caused by activation of central α2‐adrenergic systems, we examined exposure of chicks to the effects of the BZD receptor antagonist flumazenil (0.5 mg kg−1, i.p.) and GABAA antagonist bicuculline (0.1 mg kg−1, i.p.) on clonidine‐induced sleep. Bicuculline and flumazenil inhibited the increase of clonidine‐induced sleep time by MFs. Clonidine or MFs did not change GABA levels in the brain.

4 These results suggest that MFs can increase clonidine‐induced sleep via a change of GABAA and BZD receptor system irrespective of the concentration of GABA or noradrenaline in the brain of 2‐day‐old chicks.
A predictive model to locate ancient forests in the Cross Timbers of Osage County, Oklahoma
Authors: Therrell Matthew , Stahle David
Published: March 2003

The Cross Timbers are a mosaic of upland deciduous forest, savanna, and glade that typifies the broad ecotone between the eastern deciduous forest and the grasslands of the southern Great Plains. The pre‐settlement Cross Timbers may have covered some 7,909,700 ha from central Texas, across Oklahama into eastern Kansas, and today may represent the least disturbed forest ecosystem of comparable size still left in the eastern United States. Extensive tree‐ring research indicates that ancient forests dominated by 200 to 400 year old post‐oaks (Quercus stellata Wang) survive throughout the Cross Timbers, particularly in Oklahoma. These ancient forests persist largely because the Cross Timbers formation is non‐commercial for timber production, and has not experienced large‐scale industrial logging. Because ancient forest relics are often found on stressful non‐commercial sites in the Cross Timbers and elsewhere, it is possible to design predictive models to locate the specific terrain where undisturbed forests are likely to survive. A predictive model for southern Osage County, Oklahoma, was developed based on the steep, infertile soils of the Niotaze‐Darnell complex. We tested the model with field inspection and tree‐ring analysis of fifty randomly selected belt transects, and 74% of the sampled terrain is still old‐growth Cross Timbers woodland. This translates into 8200 ha of ancient Cross Timbers on this single site type in southern Osage County. The abundance of ancient forest in the Cross Timbers is not widely appreciated. However, large contiguous tracts of ancient Cross Timbers up to 700 ha were identified with this predictive model, strongly supporting inferences concerning the relatively undisturbed nature of this ecosystem.
Contrasting patterns of elevational zonation for birds and mammals in the Andes of southeastern Peru
Authors: Patterson Bruce D. , Stotz Douglas F. , Solari Sergio , Fitzpatrick John W. , Pacheco Victor
Published: March 2003

Abstract. To determine the generality of avian diversity patterns, we investigated patterns of elevational zonation shown by birds and mammals along the eastern slope of the Andes Mountains in southeastern Peru. The strong environmental gradient sampled, entirely within Peru's Manu National Park and Biosphere Reserve, supports highly diverse faunas. Elevational distributions of 901 bird species, 129 bat species, and twenty‐eight species of native mice exhibit contrasting patterns in species richness, species composition, and species turnover. Birds and bats showed smooth declines of species richness with elevation, whereas the richness of mouse assemblages was unrelated to elevation. For all three groups, the greatest differences were between lowland and highland faunas, although cutoff points for this contrast varied among groups (≈ 500 m for birds, 750 m for bats, and 1000 m for mice). Differences in composition also separated bird and bat faunas on either side of c. 1400 m (the boundary between montance forest and cloud forest); for mice, this faunal transition may take place nearer to 2000 m. Bird and bat faunas lacked the more discrete zonations suggested for mouse assemblages, as indicated by elevational range profiles and nested subset analyses. Distinct highland assemblages are apparent in two‐dimensional histograms of range limits of birds and mice, but not for bats. Highland bat species occupy broader elevational ranges than lowland bat species, but for both birds and mice, species at intermediate elevations had the broadest amplitudes. Finally, clumping of range maxima and minima along the gradient identified zones of pronounced species turnover in each group, but these were generally not strongly associated with the locations of ecotones.

Differences in zonation of these groups appear to reflect their different biological attributes and phylogenetic histories. Such differences obviously complicate discussions of ‘general’ diversity patterns, and limit the usefulness of birds to forecast or predict diversity patterns in other more poorly known groups—other groups may show elevated diversity and endemism in areas where avian diversity patterns appear unremarkable. The pronounced contrasts between bats and mice, and the generally intermediate character of avian patterns, suggest that future analyses might profitably partition birds into finer, more homogeneous groups of historically and/or ecologically similar species. Group differences in zonation may ultimately prove explicable with information on both species‐abundance patterns and resource distributions.
Island biogeography of the Japanese terrestrial mammal assemblages: an example of a relict fauna
Authors: Millien‐Parra Virginie , Jaeger Jean‐Jacques
Published: March 2003

AimThe aim of this paper is to provide a review of the biogeography of the terrestrial mammalian fauna from the Japanese islands.

LocationThe Japanese archipelago is located off the eastern coast of Asia. It extends over a distance of approximately 2000 km in length, from north to south, and comprises more than 3900 islands of widely differing areas.

MethodsThe list of the living and Quaternary mammalian fauna of Japan and its geographical distribution was compiled from various published works. Introduced species, marine mammals and bats were not considered in this study. Simpson and Jaccard indices were used to quantify the similarities between the fauna from twelve selected islands from the Japanese archipelago. Regression lines and Pearson correlation coefficients were used to describe the relations between species richness and various geographical factors of the islands, such as area or descriptors of isolation. Lastly, we used the method proposed by
Atmar & Patterson (1993) to measure the degree of nestedness of the Japanese terrestrial mammalian fauna.

ResultsSpecies richness on islands is highly correlated with island size. However, this study reveals the importance of non‐equilibrium effects. At a large scale, the current distribution of mammals in Japan seems to be due to selective post‐glacial extinction processes. A large proportion of the Japanese mammals are endemic forms, and extinctions were not balanced by the colonization of species from the Asiatic mainland. In addition, we show the major role played by inter‐island dispersal processes, in particular from larger islands towards smaller ones, that are mainly effected by the presence of deep marine channels between islands.

Main conclusionsThe present distribution of the terrestrial mammalian fauna from Japan is thus mainly the result of post‐glacial extinctions that were not compensated for by colonization of new species from the faunal Asiatic mainland source pool. However, this study emphasizes the importance of inter‐island dispersal processes.
Long distance migration of insects to a subantarctic island
Authors: Greenslade Penelope , Farrow Roger A , Smith Jeremy M. B.
Published: March 2003

Transoceanic migration of four species of macrolepidoptera to subantarctic Macquarie Island has been detected in 7 out of 33 years during the period 1962–96 and is restricted to spring and autumn. Analyses of synoptic charts during the migration period show that autumn immigrants originated from New Zealand and comprised a single species of noctuid moth,Agrotis ipsilon (Walker). Spring immigrants originated from Australia and comprised two noctuids, Dasypodia selenophora Guenée and Persectania ewingii Westwood and a butterfly, Vanessa kershawi (McCoy). Autumn migrations were associated with depressions in the southern Tasman Sea. Spring migrations were associated with the eastward passage of prefrontal airflows ahead of cold fronts which extended from southern Australia to the west of Macquarie Island. In an analysis of one of these events, winds exceeded 30 ms−1 at 300 m altitude and could have transported migrants from Tasmania to Macquarie Island overnight in less than 10 h. Flight activity was assisted by the presence of a nocturnal temperature inversion that maintained upper air temperatures above 5 °C. The effect of potential global warming on the migration and colonization of Macquarie Island by insects is discussed.
Relationship between vegetation and environmental conditions in the northern Pantanal of Mato Grosso, Brazil
Authors: Zeilhofer Peter , Schessl Michael
Published: March 2003

This paper analyses the relationship between the distribution of tropical floodplain vegetation and environmental factors such as the soil types, their physical‐chemical properties and inundation dynamics in the northern Pantanal of Mato Grosso, Brazil. Fifty‐four soil profiles of the four principal geomorphologic units of the lowland were classified into twenty‐one units of the FAO‐UNESCO system and related to eight vegetation formations. Under the deciduous and semideciduous woodland and forest formations on flood free riverbanks and relict dunes Arenosols, Solonetz and Alisols dominate. Inundation forests grow on a large variety of soil groupings such as Alisols, Solonetz, Fluvisols, Gleysols and Cambisols, mainly on fluvial deposits. Under the grassland formations of periodically flooded spreadings and depressions Planosols, Acrisols, Alisols, Fluvisols, Arenosols and Cambisols were cored, while Gleysols are common on swamps bearing Thalia geniculata or Cyperus giganteus. Canonical Correspondence Analysis was applied to study the influence of monitored environmental factors on spatial distribution of vegetation formations. Water regime and soil texture were found to define the grassland‐forest boundaries as well as the transition between different grassland formations and between seasonal as well as evergreen forests.
How isolated are Pleistocene refugia? Results from a study on a relict woodrat population from the Mojave Desert, California
Authors: Smith Felisa A. , Matocq Marjorie D. , Melendez Karla F. , Ditto Amy M. , Kelly Patrick A.
Published: March 2003

Pleistocene vicariance is often invoked to explain the disjunct populations of animals in habitat refugia throughout the southwestern United States. The combined effects of small population size and isolation from the rest of the contiguous range are thought to result in genetic differentiation of relict organisms.

Here, we describe a relict population of dusky‐footed woodrats (Neotoma fuscipesBaird) found in a pinyon‐juniper‐oak community in a small mountain range within the Mojave Desert. We compare morphological and genetic data for these individuals with two populations within the contiguous range, and with another species of woodrat (Neotoma lepida). We also examine the distributional overlap between contemporary oak species and dusky‐footed woodrats, and estimate the potential oak woodland habitat available during the late Quaternary.

As expected, both the morphological and genetic analysis confirm that the relict population isN. fuscipes. Within the limitations of our data, we detect no evidence of differentiation. Instead, the relict population forms a paraphyletic group with the nearest population within the contiguous range. This may be explained by the combined influences of a shorter period of isolation and a greater effective population size than was originally expected.

The linkage between contemporary oak and dusky‐footed woodrat distributions is very tight, reinforcing the idea of an obligate relationship between the two.

We estimate that at ~8000 ybp, pinyon‐juniper‐oak woodlands may have covered ~53% of the central Mojave, forming large contiguous areas of habitat. Although considerably more fragmented, at present ~12% of the area consists of relict woodlands.

Our results suggest that there may be numerous other woodrat refugia, with a relatively high degree of connectiveness between the larger ones. Animals within them may effectively function as a single metapopulation, buffering against occasional stochastic extinction events.
Cladistic biogeography of the Mexican transition zone
Authors: Marshall C. J. , Liebherr J. K.
Published: March 2003

Biogeographic relationships among nine montane areas of endemism across the transition zone between North and South America are analysed cladistically based on phylogenetic hypotheses of thirty‐three resident monophyletic taxa of insects, fish, reptiles, and plants.

Areas of endemism include the Arizona mountains (AZ), Sonoran Desert (SD), Sierra Madre Occidental (OCC), southern Sierra Madre Occidental (SOC), Sierra Madre Oriental (ORI), Sierra Transvolcanica (TRAN), Sierra Madre del Sur (SUR), Chiapan‐Guatemalan Highlands (CGH), and Talamancan Cordillera (TC).

Area relationships are summarized using Brooks Parsimony Analysis and Assumption 0, with the former resulting in more defensible biogeographic hypotheses.

Areas of endemism are dividable into two monophyletic groups; a northern group including AZ, SD, OCC, and ORI, and a southern group consisting of TC, CGH, TRAN, SUR, and the isolated southern regions of the Sierra Madre Occidental (SOC).

The northern set of areas are characterized by recent, probably Pleistocene, isolation and prevalent widespread species, whereas the southerly areas probably diverged after Pliocene closure of the Panamanian isthmus.

The southern areas are redundantly represented on many of the taxon‐area cladograms by endemic species, indicative of much higher levels of endemism in the Sierra Transvolcanica and further south.

Use of a general area cladogram in such a transition zone permits explicit exploration of biogeographic patterns and establishes a predictive framework for taxonomy and conservation prioritization.