bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of cardiovascular responses to adenosine A1 receptor stimulation in the posterior hypothalamus of anaesthetized rats by cAMP and by GABAB receptor blockade
Authors: Lee H. H. , Koh H. C. , Chae S. L. , Kang J. S. , Lee C. H. , Paik D. J. , Shin I. C. 
Published: March 2003

Summary 1 Injection of N6‐cyclohexyladenosine (CHA; 1, 5 and 10 nmol), an adenosine A1 receptor agonist, into the posterior hypothalamus of rats produced a dose‐dependent decrease in blood pressure (BP) and heart rate (HR). 2 Pretreatment with 8‐cyclopentyl‐1,3‐dimethylxanthine (CPDX; 50 nmol), an adenosine A1 receptor antagonist, blocked the depressor and bradycardic effects of CHA (10 nmol). 3 Pretreatment with 8‐bromo‐cyclic adenosine monophosphate (AMP) (10 nmol), a cAMP analogue, attenuated the depressor and bradycardic effect of CHA (10 nmol); 8‐bromo‐cyclic guanosine monophosphate (GMP) (10 nmol), a cGMP analogue, did not modify those effects of CHA. 4 In addition, pretreatment with 5‐aminovaleric acid (25 nmol), a γ‐aminobutyric acid (GABA)B receptor antagonist, attenuated the depressor and bradycardic effects of CHA (10 nmol). 5 These results suggest that adenosine A1 receptors in the posterior hypothalamus have an inhibitory role in the central cardiovascular regulation and that these vasodepressive and bradycardic actions are modified by raised cAMP and by GABAB receptor inhibition.
Soil properties and seedling establishment in soils from monodominant and high‐diversity stands of the tropical deciduous forests of México
Authors: Martijena Nora E. 
Published: March 2003

Abstract. The hypothesis that soils from mature monodominant forests are unfavourable for establishment of tree species other than the dominant was tested for a lowland tropical deciduous forest with stands dominated by Celaenodendron mexicanum Standl. (CS). This species of Euphorbiaceae occurs almost exclusively in monodominant stands in which recruitment of other species appears to be poor. Soil properties were examined and experiments were conducted on germination and establishment of Celaenodendron mexicanum and three other species common in adjacent high‐diversity mixed stands (MS): Recchia mexicana Moc. & Sessé, Caesalpinia eriostachys Benth., and Cordia alliodora (Ruiz & Pav.) Oken. Soil moisture regimes are affected by topographic position in the study area, but Celaenodendron mexicanum was found occupying hillsides as well as flatlands, and slope gradients of its stands were typical of the region. The microsites occupied in relation to soil moisture and light availability also appear to be undistinctive. There were no significant differences between stand types in any soil property (pH, O.C., total N, total P, avail. P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn concentrations). A stand of intermediate dominance of Celaenodendron (ICS) did not differ from its adjacent mixed stand (MS) in soil texture or most of the nutrients tested; however, seasonally restricted differences in the contents of Fe and Mn (ICS<MS) were detected. In fact, the contents of most nutrients in all the stands changed significantly between seasons: mostly, they were lower in the wet season.Germination percentages and seedling survival to 4 months did not differ between CS and MS soils in greenhouse tests, and in field tests Caesalpinia eriostachys established in both stand types.The results suggest that the distinction between monodominance and high diversity is not maintained by some simple physiological restriction on the establishment of new seedlings.
Models of large‐scale breeding‐bird distribution as a function of macro‐climate in Ontario, Canada
Authors: Venier L. A. , McKenney D. W. , Wang Y. , McKee J. 
Published: March 2003

Summary Aim We modelled the relationship of breeding evidence for five species of forest songbirds (ruby‐crowned kinglet (Regulus calendula) Blackburnian warbler (Dendroica fusca), black‐throated blue warbler (Dendroica caerulescens), bay‐breasted warbler (Dendrioca castanea) and Connecticut warbler (Oporornis agilis)) and a variety of macro‐climate variables to examine the importance of climate as a factor determining distribution of breeding in these species and to assess the usefulness of spatial predictions generated from these models. Location Modelling was conducted over the entire province of Ontario, Canada, an area of ≈900,000 km2. Methods Data on the distribution of breeding in the province was derived from the Breeding Bird Atlas of Ontario. We used logistic regression to model the relationship between the probability of breeding (assessed in 10 km×10 km blocks) and estimates of a variety of climate variables at the same scale. Models were selected that had the least number of explanatory variables while at the same time having close to the best possible classification accuracy. Results The final models for these five species had from one to six explanatory variables and an overall concordance of 70.4% to 86.3% indicating a good classification accuracy. Results from subsampling 50% of the original data ten times indicate that (1) the classification accuracy of the model for data used to generate the model is not very sensitive to the specific observations used to generate the model (2) the classification accuracy of test data is close to the classification accuracy of the model data and (3) the classification accuracy of the test data is not dependent on the specific observations used to generate the model. We generated a spatial prediction of the probability of occurrence of each species for Ontario using the relationships defined by the logistic regression models and using 1 km gridded estimates of the necessary climate variables. These probability maps closely matched the maps of observed evidence of breeding from the Atlas. Main conclusions Although mechanisms controlling breeding distribution cannot be determined using this method, we can conclude that (1) macro‐climate is an important factor directly and/or indirectly determining distribution of breeding in these species and (2) spatial predictions of probability of breeding are accurate enough to be useful in predicting probability of breeding in unsampled areas.
Testate amoebae and the fossil record: issues in biodiversity
Authors: Charman Dan J. 
Published: March 2003

SummaryBiodiversity assessment is broadly divided into a consideration of species diversity, genetic diversity and ecosystem diversity. Individual species are readily defined for many groups of organisms and their relationship with fossil taxa found in the Late Quaternary is clear. Testate amoebae are a group of protozoa which form external tests that are preserved in peat and lake sediments. The higher taxa levels are defined by the morphology of the soft pseudopodia which are not preserved in fossil specimens but many lower taxa can be recognized by test characteristics. Two sets of problems occur in the assessment of fossil testate amoebae biodiversity, related to species definitions based on morphological criteria in living specimens, and the preservation and study of fossil tests. The biological species concept cannot be readily applied to testate amoebae and morphospecies are therefore defined on the basis of the characteristics of pseudopodia and tests. However, the accepted degree of intraspecific morphological variation appears to be variable between authorities and the number of described species is therefore poorly defined. In addition, there is likely to be no straightforward relationship between species diversity and genetic diversity. Further problems of species differentiation are encountered in fossil specimens so that the assessment of biodiversity in fossil populations is even more problematic. The variable results which can be obtained by the adoption of different sets of species definitions are illustrated with respect to fossil faunas from peat profiles in Canada and the UK. The biodiversity of living testate amoebae and other groups of lower organisms is poorly known and further consideration needs to be given to the definition and description of both living and fossil specimens if these problems are to be resolved. The assessment of complete ecosystem biodiversity is not possible without this and investigations which consider the role of diversity in ecosystem functioning cannot even begin.
Size and shape variability in relation to species differences and climatic gradients in the African rodent Oenomys
Authors: Renaud Sabrina 
Published: March 2003

Summary AimThe modern African murine rodent Oenomys is a semiarboreal genus characteristic of the rain forest zone. The size and shape geographical differentiation is studied in order to discuss the possible evolutionary patterns and constraints leading to this distribution. LocationTwo species of Oenomys have been previously recognized, corresponding to the West African forest block on the one hand and to the main forest block on the other hand. Both species have been sampled, and forty localities permit the study of the whole geographical range of Oenomys, from Guinea to Kenya. MethodsA Fourier analysis applied to the outlines of the first upper and lower molars allows a quantification of the size and shape variations across the geographical range of Oenomys. ResultsThis morphometrical analysis defines three morphological groups of Oenomys, corresponding to the West, Central, and East African forest zone. This result suggests the existence of an additional cryptic species. The Western group is characterized by broad asymmetrical molars and a small size. The Central African group has more elongated and larger molars while the Eastern African group displays extremely constricted molars and a small size. Main conclusion The shape can be considered as charactheristic of each group and its variations appear to be mostly related to phylogeny while size exhibits variations within each group related to climatic gradients. This discrepancy could be related to different genetic determinants for both characters, the shape being strongly genetically constrained while size can vary according to a wide range of environmental factors.
Insights into the processing of carbon in the South Florida Cypress Wetlands: a whole‐ecosystem approach using network analysis
Authors: Bondavalli Cristina , Ulanowicz Robert E. , Bodini Antonio 
Published: March 2003

AbstractAimThe aim of this research was to investigate the potential of the South Florida Cypress Wetlands as a carbon‐accumulating system.LocationThis ecosystem is part of the Big Cypress Natural Preserve, located in the south‐west part of Florida (USA) between the Mangrove Swamps that border the Gulf of Mexico and the Everglades.MethodsThis investigation was carried out by constructing networks of carbon exchange between the living and nonliving components that comprise this ecosystem. By means of these networks potential for carbon accumulation has been assessed by identifying and quantifying pathways for the transfer of carbon, assessing the efficiency between trophic levels, and evaluating the importance of material cycling. These analyses are commonly referred to as network analysis.ResultsResults obtained show that dependency on detritus by higher trophic levels is rather low and so is the trophic efficiency. Yet, less than 10% of the carbon that flows through the system is recycled and the magnitude of internal ascendency reaches only 40% of the total system ascendency.Main conclusionsAll these results support the hypothesis that the South Florida Cypress Wetlands are predominately flow‐through in nature and that carbon accumulation in this environment is noticeable.
Pollen‐based reconstructions of Japanese biomes at 0, 6000 and 18,000 14C  yr  bp
Authors: Takahara Hikaru , Sugita Shinya , Harrison Sandy P. , Miyoshi Norio , Morita Yoshimune , Uchiyama Takashi 
Published: March 2003

AbstractA biomization method, which objectively assigns individual pollen assemblages to biomes ( Prentice et al., 1996
), was tested using modern pollen data from Japan and applied to fossil pollen data to reconstruct palaeovegetation patterns 6000 and 18,000 14C yr bp Biomization started with the assignment of 135 pollen taxa to plant functional types (PFTs), and nine possible biomes were defined by specific combinations of PFTs.Biomes were correctly assigned to 54% of the 94 modern sites. Incorrect assignments occur near the altitudinal limits of individual biomes, where pollen transport from lower altitudes blurs the local pollen signals or continuous changes in species composition characterizes the range limits of biomes. As a result, the reconstructed changes in the altitudinal limits of biomes at 6000 and 18,000 14C yr bp are likely to be conservative estimates of the actual changes.The biome distribution at 6000 14C yr bp was rather similar to today, suggesting that changes in the bioclimate of Japan have been small since the mid‐Holocene.At 18,000 14C yr bp the Japanese lowlands were covered by taiga and cool mixed forests. The southward expansion of these forests and the absence of broadleaved evergreen/warm mixed forests reflect a pronounced year‐round cooling.
Juvenile tree growth rates and species sorting on fine‐scale soil fertility gradients in a Chilean temperate rain forest
Authors: Lusk Christopher H. , Matus Francisco 
Published: March 2003

AbstractAimWe sought to clarify the role of juvenile tree growth rates in species sorting along fine‐scale fertility gradients in the coast range forests of southern Chile.LocationIn montane forests in the coast range, the conifer Fitzroya cupressoides occupies the poorest soils, whereas dominance shifts to the evergreen angiosperms Nothofagus nitida and/or Weinmannia trichosperma on moderately infertile sites. On the most fertile sites, N. nitida is usually the sole overstorey dominant.MethodsWe examined the effects of soil depth and nitrogen availability on height growth and leaf nitrogen levels of the three common overstorey dominants. Sapling height growth rates and foliage nitrogen concentration were measured in 20 large gaps (>0.1 ha), on sites of varied soil depth and potential N‐mineralization rates.ResultsHeight growth rates of Weinmannia and Nothofagus were strongly positively correlated with both soil depth and potential N‐mineralization. Height growth of Fitzroya was strongly correlated with soil depth, but not with N‐mineralization. Nothofagus and Weinmannia enjoyed large growth‐rate advantages over Fitzroya on the more fertile soils of the study area, and this advantage was reduced or nullified (but not reversed) on poor soils. This pattern was associated with species differences in nitrogen use: on fertile soils, Nothofagus and especially Weinmannia, achieved more height growth per unit of leaf N than Fitzroya, whereas differences were minimal on poor soils.Main conclusionsResults suggest that comparative height growth rates of juvenile trees, associated with nitrogen productivity differences, play a key role in determining eventual dominance on productive sites, but that traits other than growth (possibly related to nutrient retention) are more important on low fertility sites. Disturbance regimes appear to vary in relation to site fertility, and differential species responses to this superimposed disturbance gradient are also probably influential in determining overstorey composition.
Biogeography of the southern cool‐temperate galaxioid fishes: evidence from metazoan macroparasite faunas
Authors: McDowall R. M. 
Published: March 2003

AbstractAimThis study seeks evidence for coevolution between the galaxioid fish families, Galaxiidae and Retropinnidae, and their macroparasites as a means of adding to our understanding of the biogeography of the fish families.LocationThese families are characteristic southern cool‐temperate elements in the fish faunas of Australia, New Zealand and southern South America and some southern/sub‐Antarctic islands.MethodsThe analysis is based on a review of the literature.ResultsAnalysis showed that in each area fish species have parasites that are representative of the general fish parasite faunas of that area, rather than those characteristic of, or specific to, either these galaxioid families or the genera and species that they contain. In many instances the parasites also infect exotic fish species introduced into each area.Main conclusionsThere is little evidence that parasite faunas have coevolved with the fish hosts. Parasite data therefore provide little support for a vicariance biogeography of galaxioid fishes in the southern cool‐temperate region. Also, the data do not conflict with dispersal hypotheses for that biogeography.
A relict population of Fagus grandifolia var. mexicana at the Acatlan Volcano, Mexico: structure, litterfall, phenology and dendroecology
Authors: Williams‐Linera Guadalupe , Devall Margaret S. , Alvarez‐Aquino Claudia 
Published: March 2003

AbstractAim  Fagus grandifolia var. mexicana (Martinez) Little has an extraordinarily restricted distribution in the Mexican montane cloud forests. Isolated Fagus (beech) populations have been recorded in less than 10 small areas (2–40 ha) in the eastern Sierra Madre at altitudes from 1400 to 2000 m. The objectives were to determine tree and seedling age, forest structure, phenology, litterfall patterns and the relationship between mast and climatic variables.Location  We report on three Fagus stands at the Acatlan Volcano, Veracruz, Mexico.Methods  Changes in forest cover were determined using aerial photographs. Within each stand, basal area, density and tree species composition were determined in a 0.1‐ha band transect. Additionally, litterfall production was quantified and phenophases were recorded monthly over a 3‐year period, and 60 tree cores were collected to determine age distribution and tree‐ring growth.Results  The forest was atypical in several respects. Fagus was the only dominant tree species in the crater stand, although in the rim and at the top of the volcano it was codominant with other tree species. Juveniles occurred only on the rim, but there was a seedling bank in the crater. Although forest cover in the area increased between 1968 and 1993, the Fagus stands did not change in size. Leaf production peaked in March and April, and leaf fall occurred from October through February. Litterfall production was the highest in November. During mast years, flowering started in February and between mast events there were no flowers or fruits. Minimum temperatures were highly correlated with Fagus litterfall and leaf fall. Seedlings ranged in age from 2 to 18 years and were 13–60 cm tall. Tree cores ranged from 76 to 120 years, but trees were older than the core samples.Main conclusions  Although beech is considered a gap regeneration species that reaches the canopy after alternating periods of release and suppression, the trees in the crater were released when less than 1.5 m tall and have suffered few periods of suppression since. The results indicate that the crater stand was established after a severe disturbance destroyed the existing forest. We conclude that the relict beech population should be able to maintain itself, if not severely disturbed by humans or by climatic changes related to global warming.
Species richness and endemism in the Western Australian flora
Authors: Beard J. S. , Chapman A. R. , Gioia P. 
Published: March 2003

AbstractAim  Estimates of endemic and non‐endemic native vascular plant species in each of the three Western Australian Botanical Provinces were made by East in 1912 and Beard in 1969. The present paper contains an updated assessment of species endemism in the State.Location  Western Australia comprises one third of the continental Australian land mass. It extends from 13° to 35° S and 113° to 129° W.Methods  Western Australia is recognized as having three Botanical Provinces (Northern, Eremaean and South‐West) each divided into a number of Botanical Districts. Updated statistics for number of species and species endemism in each Province are based on the Census of Western Australian Plants data base at the Western Australian Herbarium (Western Australian Herbarium, 1998 onwards).Results  The number of known species in Western Australia has risen steadily over the years but reputed endemism has declined in the Northern and Eremaean Provinces where cross‐continental floras are common. Only the isolated South‐West Province retains high rates of endemism (79%).Main conclusions  With 5710 native species, the South‐West Province contains about the same number as the California Floristic Province which has a similar area. The Italian mediterranean zone also contains about this number but in a smaller area, while the much smaller Cape Floristic Region has almost twice as many native species. The percentage of endemic species is highest at the Cape, somewhat less in south‐western Australia and less again in California. Italy, at 12.5%, has the lowest value. Apart from Italy, it is usual for endemism to reach high values in the largest plant families. In Western Australia, these mainly include woody sclerophyll shrubs and herbaceous perennials with special adaptations to environmental conditions. While those life forms are prominent in the Cape, that region differs in the great importance of herbaceous families and succulents, both of which are virtually absent from Western Australia. In California and Italy, most endemics are in families of annual, herbaceous perennial and soft shrub plants. It is suggested that the dominant factor shaping the South‐West Province flora is the extreme poverty of the area’s soils, a feature that emphasizes sclerophylly, favours habitat specialization and ensures relatively many local endemic species.