bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seedling establishment in an Australian tropical savanna: effects of seed supply, soil disturbance and fire
Authors: Setterfield S. A. 
Published: March 2003

Summary

Australia's savannas typically are burnt every 1–3 years. Although there are concerns about the effect of frequent fire on recruitment of Australian savanna species, there is a lack of information. This research aimed to determine whether seed or microsite availability limits seedling recruitment of the overstorey tree Eucalyptus miniata and the midstorey shrub Acacia oncinocarpa, whether seed or microsite availability is affected by frequent fire, and the consequent effect on seedling recruitment.
Quadrats were established in unburnt areas. Experimental manipulations were addition of seed and/or disturbance of the soil surface to increase the number of microsites suitable for germination. In a second experiment, seed was added to quadrats established in three fire regimes after the annual burning event (unburnt, burnt early in the dry season, burnt late in the dry season).
In unburnt areas, seedling regeneration was limited by both seed supply and microsite availability. Both burning regimes reduced seedling emergence, possibly because the reduced canopy cover caused unfavourable microclimate, the increased grass and forb ground cover increased competition for resources, and there was increased loss of seed to seed harvesters.
The results indicate that sexual regeneration of these common species is disadvantaged by current burning practices because both seed supply and the number of microsites are reduced. Thus, long‐term changes in savanna floristic structure seem likely unless fire managers aim to increase the fire‐free intervals. The relative abundance of species able to reproduce vegetatively may increase under frequent fire regimes. Such a change may take a long time to detect given the fire‐resistant and long‐lived nature of overstorey species, and the capacity for vegetative regeneration in many savanna species. The impacts of fire on limiting seedling regeneration will require savanna managers to consider fire‐free intervals of several years for effective recruitment of dominant woody species.
Modulation by nitric oxide of spontaneous mechanical activity in rat proximal colon
Authors: Mulè F. , D’Angelo S. , Amato A. , Contino I. , Serio R. 
Published: March 2003

Summary 1 In order to examine the role of nitric oxide (NO) in the tonic neural inhibition in rat proximal colon, the effects of Nω‐nitro‐
l‐arginine methyl ester (L‐NAME) were studied on the spontaneous contractions of circular muscle (monitored as intraluminal pressure changes) and of longitudinal muscle (detected as isometric tension changes). 2 L‐NAME (3 × 10−−6–3 × 10−−4 m) caused a concentration‐dependent increase in the amplitude of circular contractions, without affecting those of longitudinal muscle. This effect was prevented by
l‐arginine (1–5 × 10−−3 m), but not
d‐arginine. 3 In the presence of tetrodotoxin (10−−6 m), which per se induced increase of the pressure waves, L‐NAME (10−−4 m) caused no further effects on the amplitude of the spontaneous contractions. 4 The response to L‐NAME (10−−4 m) was unaffected by atropine (10−−6 m), guanethidine (10−−6 m), hexamethonium (up to 3 × 10−−4 m) or α‐chymotrypsin (up to 5 U ml−−1). 5 NK2 receptor antagonists, SR 48968 (3 × 10−−6 m) or MEN 10627 (10−−6 m), produced a reduction of the amplitude of the pressure waves but failed to affect the contractile response to L‐NAME (10−−4 m). 6 These findings suggest that tonic production of NO from inhibitory neurones influences the degree of contractions of circular muscle. An involvement of an inhibitory peptide as well as disinhibition of cholinergic or NK2‐tachykinergic excitatory neurotransmission in the mechanism of NO action can be ruled out.
Catecholamines in hyperpnoea‐induced airway constriction of guinea pigs
Authors: Lai Y.‐L. , Lee S.‐C. , Lai L.‐C. , Hu F.‐C. , Tsai T.‐L. , Tsai Y.‐F. 
Published: March 2003

1 We found previously that propranolol augments hyperpnoea‐induced bronchoconstriction (HIB). This study was performed to investigate the underlying mechanism of this aug‐ menting action of propranolol. 2 In the first series, 45 young Hartley guinea‐pigs were divided into five groups: control; propranolol; adrenalectomy; metoprolol and reserpine. Each animal underwent three periods: baseline, hyperpnoea, and recovery. For each animal 1 ml of arterial blood was sampled during the baseline and recovery periods. 3 Treatments of propranolol, metoprolol, and reserpine caused significant decreases in both dynamic respiratory compliance (Crs) and forced expiratory volume in 0.1 s (FEV0.1) during the baseline period. Hyperpnoea caused slight but not significant decreases in Crs, FEV0.1, and maximal expiratory flow at 50% total lung capacity (TLC) (V˙max50) during the recovery period in the control group. Propranolol, but not other treatments, significantly augmented these decreases (indicating HIB). Plasma noradrenaline and adrenaline levels in the reserpine group were not detectable. The above treatments or hyperpnoea did not induce any significant effect on the plasma noradrenaline level. Plasma adrenaline level of the control group was higher than that of either adrenalectomy or reserpine group during the baseline and the recovery periods. 4 In the second series, we avoided repeated blood samplings. Forty‐eight animals were evenly divided into two groups: control and propranolol. Each group was again evenly divided into three subgroups: baseline; hyperpnoea, and recovery. Five minutes into the recovery period, we demonstrated HIB in the control group. In terms of V˙max50, this HIB was significantly augmented by propranolol. Plasma noradrenaline and adrenaline levels, however, were not significantly altered by either hyperpnoea or propranolol. 5 Taken together, these data suggest that propranolol‐augmented HIB has no direct relationship with decreased catecholamine activity.
Faunal relationships and zoogeographical affinities of mammals in north‐west Africa
Authors: Dobson Mike , Wright Amanda 
Published: March 2003

AbstractThe nonmarine mammal fauna of the Maghreb region of north‐west Africa is related to that from three potential source areas: the northern Palaearctic (Europe and south‐west Asia; here referred to as the European fauna), subsaharan Africa (the African fauna) and the arid Palaearctic (Sahara Desert: the desert fauna).On the basis of geographical distribution patterns, this fauna divisible into two groups: the bats, whose affinities are most closely related to southern Europe and south‐west Asia, and nonflying species, most closely related to subsaharan Africa but with an appreciable northern Palaearctic element. These affinities are even more pronounced if desert fauna are removed from the analysis.The nonflying European fauna probably colonized via south‐west Asia and north Africa, rather than direct from western Europe.The results demonstrate that terrestrial habitat barriers are less of an impediment to dispersal, for all mammals except bats, than even narrow stretches of water.The fauna of the Maghreb may be undergoing faunal relaxation, following immigration from tropical Africa and south‐west Asia during mesic phases in the Late Pleistocene and early Holocene.
Evidence for the widespread occurrence of ancient forests on cliffs
Authors: Larson D. W. , Matthes U. , Gerrath J. A. , Larson N. W. K. , Gerrath J. M. , Nekola J. C. , Walker G. L. , Porembski S. , Charlton A. 
Published: March 2003

AbstractAimThe objective of this work was to determine if the existence of ancient forests on cliffs was specific to the Niagara Escarpment, Canada, or part of a globally widespread pattern.LocationSixty‐five cliff sites were visited in five countries in the temperate climatic zone, and trees were sampled for age and growth rate on forty‐six of these.MethodsTwo hundred and twenty‐four core samples or cross‐sections were taken from trees on cliffs that varied in height, aspect, rock‐type, and exposure. General observations were also made of regeneration of the tree species forming the mature canopy, and other habitat conditions.ResultsThe evidence shows that ancient slow‐growing forest occurs on most cliffs. Age and growth rate distributions were similar at all treed sites. Small‐staturedThuja, Juniperus, orTaxusstems with age estimates in excess of 1000 years were found in the United States, the United Kingdom and France, and smallPinus and Quercusstems nearly 400 years in Germany. There was a high rate of recurrence of plants in the generaPolypodium,Asplenium,Cystopteris,Campanula,Rosa,Prunus,Hedera, andSorbus. Most of the sites appear to be habitats of completely natural origin.ConclusionsWe conclude that ancient natural forest is a normal feature of cliffs, at least in the temperate zone.
Pollen‐based biome reconstruction for southern Europe and Africa 18,000 yr bp
Authors: Elenga H. , Peyron O. , Bonnefille R. , Jolly D. , Cheddadi R. , Guiot J. , Andrieu V. , Bottema S. , Buchet G. , De Beaulieu J.‐L. , Hamilton A. C. , Maley J. , Marchant R. , Perez‐Obiol R. , Reille M. , Riollet G. , Scott L. , Straka H. , Taylor D. , Van Campo E. , Vincens A. , Laarif F. , Jonson H. 
Published: March 2003

AbstractPollen data from 18,000 14C yr bp were compiled in order to reconstruct biome distributions at the last glacial maximum in southern Europe and Africa. Biome reconstructions were made using the objective biomization method applied to pollen counts using a complete list of dryland taxa wherever possible. Consistent and major differences from present‐day biomes are shown.Forest and xerophytic woods/scrub were replaced by steppe, both in the Mediterranean region and in southern Africa, except in south‐western Cape Province where fynbos (xerophytic scrub) persisted.Sites in the tropical highlands, characterized today by evergreen forest, were dominated by steppe and/or xerophytic vegetation (cf. today’s Ericaceous belt and Afroalpine grassland) at the last glacial maximum.Available data from the tropical lowlands are sparse but suggest that the modern tropical rain forest was largely replaced by tropical seasonal forest while the modern seasonal or dry forests were encroached on by savanna or steppe. Montane forest elements descended to lower elevations than today.
Abundance–distribution relationships on interacting trophic levels: the case of lake‐nesting waterfowl and dytiscid water beetles
Authors: Elmberg Johan , Sjöberg Kjell , Pöysä Hannu , Nummi Petri 
Published: March 2003

AbstractAimTo compare patterns in local abundance, regional distribution and body size in waterfowl and dytiscid beetles sampled from the same lakes.LocationThirty Swedish lakes, 56–63° N.MethodsBirds were censused repeatedly, at which time submerged activity traps were placed on the littoral to catch invertebrates. Avian patterns were analysed separately for four different selections of species, each motivated on functional or phylogenetical grounds. Patterns in dytiscid beetles have been described earlier in Nilsson, Elmberg & Sjöberg (1994).ResultsAlthough there were large differences between individual lakes, there was no significant latitudinal gradient at the lake level in either species richness or abundance in any of the bird groupings. Lakes which were rich in species and numbers of dytiscid beetles were also rich in species and numbers of all four waterfowl groups. Three of the four bird groups conform with the general pattern of widely distributed species being more abundant locally, as do dytiscid beetles in the same lakes. Body mass and local abundance were correlated in one of the four birds groups only, i.e. dabbling ducks, (Anas spp.).Main conclusionsWe find evidence for a similar and positive local abundance–distribution relationship in dytiscid beetles and waterfowl breeding in the same lakes, but no common general pattern in local abundance vs. body size.
What is the origin of the carabid beetle fauna of dry, anthropogenic habitats in western Europe?
Authors: Andersen Johan 
Published: March 2003

AbstractAimTo study the origin of the carabid beetle fauna of dry, open anthropogenic habitats.LocationVarious parts of Europe.MethodsCollecting by hand in habitats influenced by humans (arable land, sand pits, ruderal places, road verges, meadows) and naturally open habitats such as talus, supralittoral sand dunes, alvar as well as littoral habitats in south and central Scandinavia. Studies made in other parts of Europe were included in the discussion.Results and conclusionThe material comprises about 37,700 specimens. About 8% of the Scandinavian species occurring in anthropogenic habitats may have a littoral origin, about 10% may originate from forests whereas about 9% are euryoecious. A majority of the species (about 66%) originate from primarily open, dry habitats and many of them constitute a steppe or steppe‐like element. They invaded the bare landscape soon after the deglaciation and probably survived in naturally open habitats (supralittoral sand dunes, talus, alvar, old riverbeds) during the postglacial warm period, but some species have a recent origin in Scandinavia.
The flora of the South Sandwich Islands, with particular reference to the influence of geothermal heating
Authors: Convey P. , Lewis Smith R. I. , Hodgson D. A. , Peat H. J. 
Published: March 2003

AbstractAim  To carry out as comprehensive a survey as practicable of the flora (higher plants, mosses, liverworts, lichens, basidiomycete fungi and diatoms) of the isolated, volcanically active, South Sandwich Islands archipelago in the southern South Atlantic. To relate the components of this flora to (1) the influence of local geothermal heating and (2) wider regional floras.Location  South Sandwich Islands, southern South Atlantic Ocean, maritime Antarctic (56–60° S, 26–28° W).Methods  Ice‐free accessible sites on all 11 of the major islands in the archipelago were visited by helicopter in January 1997. During each visit, voucher specimens of each floral group were collected. The comprehensiveness of collections obtained at each site varied with the duration of each visit (a function of tight logistic constraints) and extent of site. Visit duration varied from 1 to 9 h at most sites, with longer periods spent on Bellingshausen Island (2 days) and Leskov Island (1 day). Candlemas Island was examined in greater detail over a 4‐week period in February 1997. At all sites, particular attention was given to areas influenced by geothermal heating.Results  Data obtained in 1997 are combined with updated records from the only previous survey (in 1964) to provide a baseline description of the flora of the archipelago, which currently includes 1 phanerogam, 38 mosses, 11 liverworts, 5 basidiomycete fungi, 41 lichenised fungi and 16 diatoms with, additionally, several taxa identified only to genus. Major elements of the moss and liverwort floras are composed of South American taxa (32% and 73%, respectively), with a further 45% of mosses having bipolar or cosmopolitan distributions. These two groups show low levels of Antarctic endemicity (11% and 18%, respectively). In contrast, 52% of lichens and 80% of basidiomycete fungi are endemic to the Antarctic. A further 36% of lichens are bipolar/cosmopolitan, with only 5% of South American origin.Main Conclusions  The flora of the South Sandwich Islands is clearly derived from those of other Antarctic zones. The flora of unheated ground is closely related to that of the maritime Antarctic, although with a very limited number of species represented. That of heated ground contains both maritime and sub‐Antarctic elements, confirming the importance of geothermal heating for successful colonisation of the latter group. The occurrence of several maritime Antarctic species only on heated ground confirms the extreme severity of the archipelago’s climate in comparison with well‐studied sites much further south in this biogeographical zone.
The biogeographical relations of the frogs and snakes of Sundaland
Authors: Inger Robert F. , Voris Harold K. 
Published: March 2003

AimWe seek to relate the present distributions of frogs and snakes of Sundaland and the known geological history of the region.LocationFrom the Isthmus of Kra to Java and Sulawesi.MethodsWe relate the known ecological requirements of frogs and snakes to their geographical distributions and information on geological history.ResultsMicrohabitat requirements for larvae of various groups of frogs are strong predictors of the breadth of their geographical distributions. At the species level, the frog faunas of the Malay Peninsula and Sumatra are the most similar. The Sulawesi frog fauna, mainly derived from Sundaland lineages, shows almost no similarity to the other frog faunas at the species level. The ecological zones occupied by snake species show association with the breadth of their geographical distributions There are only minor differences among similarity ratios for the Malay Peninsula–Sumatran, Malay Peninsula–Borneo, and the Borneo–Sumatra pairs. The Sulawesi snake fauna has distinctly lower similarity with the faunas of the other areas. The similarity ratios between faunas are larger for snakes than for frogs. This difference between the two groups reflects the difference between them in ability to cross salt water barriers, frogs being extremely vulnerable to saline water. Also snakes may establish founder populations more easily as a single gravid female or one carrying stored sperm may introduce a clutch into previously unoccupied territory.ConclusionsA few species of frogs and snakes probably reached their present, almost ubiquitous distributions in Sundaland within the last few millenia or even more recently. Other widely distributed species may have been able to disperse among land masses within Sundaland until 10,000–17,000 yr BP; the frogs of this category are common in environments that almost certainly characterized the exposed area of the South China Sea. The distributions of other frogs common to the Malay Peninsula, Sumatra and Borneo probably antedate the Pleistocene, as their larval development requires hilly topography which was not generally available on the Pleistocene‐exposed bed of the South China Sea. Many of the endemic species of frogs and snakes probably owe their origins to events of the Miocene or earlier. Several genera of frogs and one genus of snakes have undergone extensive speciation and display considerable sympatry and elevational stratification of species, suggesting their present distributions are the result of events as old as the Eocene. We have cast these conclusions in the form of hypotheses that can be tested mainly by the use of molecular genetics, but in some cases, by additional field sampling.
Stepping stones to Hawaii: a trans‐equatorial dispersal pathway forMetrosideros(Myrtaceae) inferred from nrDNA (ITS+ETS)
Authors: Wright Shane D. , Yong Catherine G. , Wichman Stephen R. , Dawson John W. , Gardner Richard C. 
Published: March 2003

AimThe majority of Hawaii's plants are derived from the south and west of the Pacific rim, suggesting that at least some of the founders have crossed the climatic discontinuity at the equator. However, the pathways of these dispersal events are not well understood. We sought to elucidate such a pathway for the plant genusMetrosiderosBanks ex Gaertn., which appears to have colonized Hawaii from New Zealand.LocationWe have previously analysed the internal transcribed spacer (ITS) sequence of nrDNA for thirty‐six taxa ofMetrosiderossubgenusMetrosiderosdistributed across Melanesia and Polynesia. Further we collected two taxa from the Austral and Marquesas Islands.MethodsPhylogenetic analysis was undertaken using both the ITS and external transcribed spacer (ETS) regions of nrDNA for twenty‐three taxa from Polynesia and East Melanesia.ResultsThe increased resolution achieved by combining ETS data with that of ITS allowed discrimination of two subclades in eastern Oceania. One subclade groups all the Hawaiian taxa together withM. collina(J. R. & G. Forst.) A. Gray from the Marquesas Islands.Main conclusionsFrom an origin in New Zealand, the woody angiospermMetrosiderosis likely to have crossed the equator to Hawaii using a staging point in the remote Marquesas Islands. Colonization of Hawaii by the wind‐borne seed of these plants has been achieved against the flow of the prevailing Trade winds north of the equator. A possible climatic mechanism for this dispersal is described.
Towards a hierarchical framework for modelling the spatial distribution of animals
Authors: Mackey Brendan G. , Lindenmayer David B. 
Published: March 2003

AimA hierarchical framework is presented for modelling the spatial distribution of terrestrial vertebrate animals.LocationThe location of the study is the montane ash forests of the Central Highlands of Victoria, south‐eastern Australia.MethodsThe framework is illustrated using as a case study the distribution of Leadbeater’s Possum [Gymnobelideus leadbeateri McCoy, 1867, (Marsupialia: Petauridae)], a small arboreal marsupial. The framework is based upon quantifying the environmental response of a species in terms of a five‐level environmental hierarchy defined by scales (global‐, meso‐, topo‐, micro‐ and nano‐scales) that represent natural breaks in the distribution and availability of the primary environmental resources. Animal response is examined in terms of a species’ distribution as observed in four biological units (the species in toto, meta‐population/population, group/colony, and individual organism). We define the spatial occurrence and abundance of the target species in each of these units as its ‘distributional behaviour’.ResultsPredictions of the potential spatial distribution of Leadbeater’s Possum are presented at meso‐, topo‐, micro‐ and nano‐scales. These spatial predictions utilize Geographical Information System (GIS)‐based spatial models of long term mean monthly climate and terrain‐modified surface radiation, together with vegetation cover and individual tree attributes from air‐photo interpretation and field survey.Main conclusionsIdeally, species’ responses at each level in the environmental hierarchy should be empirically derived using statistical models based on field observation of a species’ distribution and abundance. Spatial modelling of species’ responses becomes problematic at finer scales because of the lack of suitable environmental data. The key characteristics of the modelling framework are generic, but the influence of additional scales and processes will be important in other ecosystems and species.
Biogeography of Indo‐Pacific Pontoniinae (Crustacea, Decapoda): a PAE analysis
Authors: De Grave Sammy 
Published: March 2003

AimPontoniid shrimps are one of the most abundant coral reef associated taxa in the Indo‐Pacific. Although taxonomically well known, their ecology, life history and biogeography appears virtually unstudied. The object of the present contribution is to derive a basin wide biogeographical hypothesis, using a limited number of operational geographic units (OGU).LocationTwelve OGU’s were selected, spanning the entire Indo‐Pacific, from the East coast of Africa and the Red Sea to the Tropical Eastern Pacific (TEP).MethodsAnalysis was based on a species by OGU matrix, in which presences (1) and putative occurrences (?) were coded. Parsimony analysis of endemicity (PAE) was applied to the data set, using Dollo and Wagner Parsimony.ResultsA hierarchical pattern of area relationships was derived, with the TEP occupying a basal position, Hawaii and French Polynesia occupy positions higher up in the cladogram, whilst the Melanesian OGU maintains a sister‐area relationship to the crown clade. The latter consists of the Indo‐Philippine area, the Australian and all Indian Ocean OGUs.Main conclusionsPontoniinae exhibit a clear hierarchical pattern of area relationships, which is congruent with previous biogeographical studies on coral reef and other taxa. The observed pattern can be explained by a combination of dispersal and vicariant events, whilst the importance of sea level changes is recognized.