bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transgenic weed beets: possible, probable, avoidable?
Authors: Desplanque Benoît , Hautekèete Nina , Van Dijk Henk 
Published: March 2003

Summary

Weed beets pose a serious problem for sugar beet Beta vulgaris crops. Traditionally, the only efficient method of weed control has been manual removal, but the introduction of transgenic herbicide‐tolerant sugar beets may provide an alternative solution because non‐tolerant weed beets can be destroyed by herbicide. We evaluated the possibility that new, transgenic, weed beets may arise by gene flow between wild and crop plants.
In a study area in northern France, weed beets were present in variable densities in sugar beet fields of up to 80 weed beet plants m−2. Weed beets arise from a long‐lived seed bank, with seeds germinating from depths of 5 cm or less. In addition, diploid F1 crop–wild hybrids and triploid variety bolters (individuals with a low vernalization requirement) were present in low densities in virtually all sugar beet fields. We found gene flow to be possible between all forms, illustrated by both overlapping flowering periods in the field and successful controlled cross‐pollinations.
The F1 crop–wild hybrids result from pollination in the seed‐production region by wild plants possessing the dominant bolting allele B for flowering without experiencing a period of cold. In the case of a transgene for herbicide tolerance incorporated into male‐sterile seed‐bearer plants, such hybrids will contain both the herbicide‐tolerance and the bolting allele. Contamination of the fields by transgenic weed beets will be the result unless bolters are removed manually. The same will apply in the case of a cytoplasmically inherited transgene.
Incorporation of the transgene into the pollinator plants will prevent the immediate formation of transgenic weed beets. However, in sugar beet fields, variety bolters may successfully cross‐pollinate with weed beets in neighbouring fields. The use of diploid pollinator plants instead of tetraploids will considerably enhance gene flow towards wild beets, and is not, therefore, an attractive option.
In conclusion, the appearance of transgenic weed beets is possible but can best be retarded if the transgene for herbicide tolerance is incorporated into the tetraploid pollinator breeding line.
Tracks and riparian zones facilitate the use of Australian regrowth forest by insectivorous bats
Authors: Law Bradley , Chidel Mark 
Published: March 2003

Summary

Documentation of habitat use by individual bat species is a key issue when assessing impacts after forests are disturbed, for example by logging.
We used bat detectors to compare bat activity in unlogged forest and regrowth forest 15 years after logging in northern New South Wales, Australia. Sites of contrasting management history were replicated at the scale of small catchments, with detectors positioned on tracks, off tracks and in riparian zones in either unlogged or regrowth forest.
The highest bat activity was recorded on forest tracks, with no significant difference between detectors in regrowth (mean = 183 passes night−1) and unlogged forest (196 passes night−1). Activity in riparian zones was intermediate (regrowth = 55 passes night−1; unlogged = 26 passes night−1), while off‐track sites in forest regrowth had the lowest activity levels (5 passes night−1). Species richness was lowest in the off‐track samples in regrowth and highest in the on‐track samples of regrowth.
An index of clutter for different vegetation layers was recorded at each site. Bat activity decreased significantly with increasing clutter formed by the layer of regrowth eucalypts and/or understorey rain forest. This result strongly suggested that low bat activity off tracks was related to vegetation clutter.
Specific identification of calls revealed that the suite of species associated with tracks included both those predicted by ecomorphology to be clutter‐sensitive (Falsistrellus tasmaniensis, Vespadelus darlingtoni, Vespadelus pumilus and Chalinolobus morio) and clutter‐tolerant (Rhinolophus megaphyllus).
Elevation and temperature were also significant covariates of activity for a number of species.
As part of sustainable management of regrowth forests, we advocate maintaining flyways for bats in the form of tracks and riparian zones, in addition to the widely recognized need for the retention of hollow‐bearing trees as roost sites. Research on the effects of silvicultural thinning, which will reduce clutter with possible benefits to some bat species, should also be a priority in forest characterized by secondary regrowth.
Dynamics of experimental vasogenic brain oedema in the rat: changes induced by adrenergic drugs
Authors: Borges N. , Sarmento A. , Azevedo I. 
Published: March 2003

1 The effects of adrenergic drugs on the formation and resolution of cerebral oedema in a rat model of cold‐induced vasogenic brain oedema were studied. Evans blue dye extravasation, water content and ultrastructural alterations (pinocytotic vesicle formation in capillary endothelial cells and apparent water accumulation in the brain parenchyma) were evaluated in parietal cortex. 2 Previous administration of the α‐adrenoceptor antagonist phenoxybenzamine produced a reduction of Evans blue extravasation and water content, diminished vesicle formation and reduced water accumulation. Previous administration of the β2‐adrenoceptor agonist clenbuterol reduced Evans blue extravasation and water content, but did not change vesicle frequency. 3 The effects of clenbuterol on Evans blue passage to the brain were blocked by timolol (β‐adrenoceptor antagonist) but not by metoprolol (selective β1‐adrenoceptor antagonist). When given after the application of cold, clenbuterol was also able to reduce Evans blue and water content in the brain. Isoprenaline (β‐adrenoceptor agonist that does not cross the blood–brain barrier) showed a reduction in Evans blue extravasation only when given intracerebroventricularly. Vinblastine (a drug that prevents vesicle formation) produced a reduction of the amount of pinocytotic vesicles. 4 We conclude that there is an influence of the central adrenergic nervous system on the formation and/or resolution of vasogenic brain oedema and that the alterations on water movement and Evans blue transport mediated by adrenergic drugs seem to be due, at least in part, to alterations of pinocytotic activity in capillary endothelial cells.
Action of tacrine on muscarinic receptors in rat intestinal smooth muscle
Authors: Becerra M. A. , Herrera M. D. , Marhuenda E. 
Published: March 2003

1 The reversible cholinesterase inhibitor, tacrine (THA) was examined against the contractions of rat duodenum to acetylcholine and carbachol (cholinesterase resistant). 2 Tacrine (10–6 M) showed a similar behaviour to physostigmine (10–6 M), changing the characters of the concentration–response curve to Ach. The contractual responses were shifted to the left at low concentrations of ACh to reveal a bell‐shaped curve with declaring contradictions at high concentrations of ACh. 3 Antagonism by atropine (10–8 M) was reduced in the presence of tacrine (10.54, dose‐ratio) compared with the shift of the curve in the absence of tacrine (73.9, dose‐ratio). The declining phase of the concentration–response curve to ACh was also antagonized by atropine. 4 Further evidence for muscarininc receptor antagonism by tacrine was a small rightward shift of the concentration‐response curve for carbachol, an agonist immune to cholinesterase. 5 This study has shown that tacrine acts both as a cholinesterase inhibitor and muscarinic antagonist on rat intestinal smooth muscle.
Global distribution of forest soil dictyostelids
Authors: Swanson Andrew R. , Vadell Eduardo M. , Cavender James C. 
Published: March 2003

Summary AimThe goal of this project was to compile, organize, and present the known distributional data on the dictyostelid cellular slime moulds (CSMs) found in forest soils worldwide. The question of what factors influence CSM distribution patterns was also addressed. LocationCSMs have been recovered from soils of temperate deciduous forest, tropical deciduous and seasonal evergreen rainforest, boreal coniferous forest, and tundra by various investigators around the world. MethodsWithin each of these four biomes, various locations around the world have been sampled by a number of investigators. The current study attempts to synthesize the known dictyostelid distributional data and present specific patterns of distribution. ResultsWorldwide, sixty‐five species of CSM were found to occupy various forest soils. These species’ distributions fell into one of four categories: cosmopolitan, disjunct, restricted, and pantropical. Main conclusionsGlobal CSM distribution patterns are influenced by a variety of factors other than the biota (including but not restricted to climate, latitude, altitude, soil pH, and soil‐forming parent materials). The current study supports the thesis that organic inputs from specific plant associations and animal vectors have an important role as well.
Fossil wood charcoal assemblages from Elands Bay Cave, South Africa: implications for Late Quaternary vegetation and climates in the winter‐rainfall fynbos biome
Authors: Cowling R. M. , Cartwright C. R. , Parkington J. E. , Allsopp J. C. 
Published: March 2003

Summary Aim The aim of this paper is to analyse fossil charcoal deposits, largely identified to the species level and spanning a sequence from the late Holocene to < 40,000 BP, in order to reconstruct Late Quaternary vegetation and climatic patterns in the western (winter‐rainfall) fynbos biome of South Africa. Location The charcoals were excavated from the Elands Bay Cave (32°19S, 18°20E) on the semiarid (200–250 mmyr−1), winter‐rainfall coastline of the western fynbos biome. Methods Patterns in the charcoal data set over time were sought by manual sorting of the charcoal×sample matrix, as well as by subjecting the data to multivariate analysis. Palaeoclimatic reconstruction was attempted by comparing the climatic controls on contemporary vegetation communities that resembled the fossil assemblages. Charcoal diversity was modelled using sample age and number of charcoal fragments as explanatory variables. Results The fossil assemblages ranged from xeric communities (similar to those presently occurring at the site) during the Holocene, to more mesic thicket and fynbos vegetation in the terminal Pleistocene, to Afromontane forest and riverine woodland communities after about 18,000 BP. Diversity of the charcoal samples increased monotonically with increasing sample age. Main conclusions The results suggest that, unlike the eastern fynbos biome, which is under fundamentally different climatic controls, soil moisture conditions in the western part of the biome were higher in the Last Glacial than during the Holocene. This scenario may help to explain the higher regional richness and associated diversification in the western than eastern part of the biome.
Competition, coexistence, and adaptation amongst rodent invaders to Pacific and New Zealand islands
Authors: Yom‐Tov Yoram , Yom‐Tov Shlomith , Moller Henrik 
Published: March 2003

SummaryVariation in skull size was investigated for three species of rats (kiore –Rattus exulans Peale; ship rat –R. rattus L.; Norway rat –R. norvegicus Berkenhout) which were introduced by humans to various islands in New Zealand and other Pacific islands. Data from seventy‐one islands and 882 specimens are examined for evidence of the effects of latitude, island size and interspecific competition among rats and the house mouse (Mus musculus L.) on skull size, using multiple regressions. For R. exulans, skull size increases with latitude as predicted by Bergmann's rule, but no such effect occurs for the other two rats. There was a positive relationship between island size and the number of species inhabiting it, and some species combinations were more likely to occur than others. For example, R. exulans and R. norvegicus were more likely to occur together, while R. rattus and R. exulans were rarely sympatric. R. exulans and R. rattus skull size was negatively correlated with the number of other rodents on the same island. R. exulans skull size increased on smaller islands in some island groups, perhaps because increased density and consequent increased intraspecific competition on smaller islands favours increased body size. This effect is more pronounced in tropical islands (Solomon islands), than in subtropical ones (Hawaiian islands) and less so in temperate New Zealand. Collectively the data demonstrate that rapid evolution of body size in predictable directions can follow within 150 years of the introduction of species to new receiving communities.
Fleshy‐fruitedness in the New Zealand flora
Authors: Lord Janice 
Published: March 2003

Summary AimIt has been claimed that the New Zealand flora has an unusually high frequency of fleshy‐fruitedness. This paper tests whether fleshy‐fruitedness is indeed more common in New Zealand than in other temperate floras, then examines the distribution of fleshy‐fruitedness among taxa and floristic elements to determine whether the flora conforms to predictions for a continental island with a relictual floristic element. Lastly, I test the extent to which fleshy‐fruitedness has influenced colonization success and subsequent speciation within New Zealand. MethodsInformation on fruit characteristics for all indigenous seed plants was extracted from the Flora of New Zealand series and analysed with χ2 tests. ResultsContrary to previous claims fleshy‐fruitedness was not unusually common in the New Zealand flora as a whole, when compared with other temperate floras. It is only more common in alpine communities and among trees. I also found no evidence for selective immigration; fleshy‐fruited New Zealand genera were not more likely, than dry‐fruited genera, to also occur in Australia. Furthermore there is no evidence that the New Zealand environment has favoured fleshy‐fruited taxa; there has been no autochthonous evolution of fleshy‐fruitedness in New Zealand, fleshy‐fruitedness has had no significant effect on speciation within New Zealand, and endemic genera are no more likely to be fleshy‐fruited than nonendemic genera. Fleshy‐fruitedness in New Zealand is, however, strongly related to floristic elements of the flora. New Zealand is a continental island and therefore, theoretically, those elements of the flora dating from a time when the landmass was less isolated, should show a more balanced representation of dispersal modes. Contrary to this, fleshy‐fruitedness is more common among species in Gondwanan taxa or in taxa with pollen records dating to before the Miocene. Main conclusionsFleshy‐fruitedness in New Zealand conforms to neither the expectations for an isolated landmasses, namely a disharmonic range of dispersal modes, nor expectations for a continental island. I suggest that this pattern may be a product of selective survival of highly vagile taxa in the low‐lying archipelago that was New Zealand during the late Cretaceous to mid‐Cenozoic, followed by an invasion by taxa with a broader range of dispersal modes facilitated by the establishment of the circumpolar current.
Characterization of the spatio‐temporal patterns of global fire activity using satellite imagery for the period April 1992 to March 1993
Authors: Dwyer Edward , Pereira José M. C. , Grégoire Jean‐Marie , DaCamara Carlos C. 
Published: March 2003

Summary Aim This paper describes the characteristics of the spatio‐temporal distribution of vegetation fires as detected from satellite data for the 12 months April 1992 to March 1993. Location Fires are detected daily at a spatial resolution of 1 km for all land areas of the globe. Methods From the fire location information a daily gridded product at 0.5° by 0.5° has been constructed. Two methods of characterizing the spatio‐temporal pattern of vegetation fires are discussed. The first applies empirical orthogonal function analysis to the monthly series of gridded data. The second approach defines and extracts a number of spatial and temporal parameters from the gridded product. The descriptive parameters extracted are used in a cluster analysis in order to group cells with similar characteristics into a small number of classes. Results Using daily global satellite observations, it is possible to characterize the spatial and temporal variability in fire activity. Most of this variability is within the tropical belt, where the majority of fire activity is concentrated, nonetheless fire was also detected in temperate and boreal regions. The period in which fire occurred varied from region to region. Parameterization provided a very synthetic view of this variability facilitating regional intercomparison. Clustering identifies five classes of fire activity, each of which can be associated with particular climatic conditions, vegetation types and land‐use. Main conclusions Global monitoring of vegetation fire from satellite is possible. The analysis provides a coherent, consistent and synoptic view of global fire activty with one data set. The type of information extracted can be of use in global atmospheric chemistry modelling and for studying the role of fire in relation to global change issues.
Genetic and morphometric diversity in Wallacea: geographical patterning in the horse shoe bat, Rhinolophus affinis
Authors: Maharadatunkamsi  , Hisheh S. , Kitchener D. J. , Schmitt L. H. 
Published: March 2003

AbstractGenetic and morphometric variation was examined in eleven island populations of the horse‐shoe bat, Rhinolophus affinis, at the easterly end of this widespread species’ range and encompassing the Australian–Oriental biogeographic interface. Allozyme variation revealed mean heterozygosity levels within islands of 0.047, which is near the mammalian average. However, heterozygosity tended to decline from west to east as populations approached the periphery of the species’ distribution, and was lowest in those islands that were separated by the greatest sea‐crossing from source populations. There is extensive between‐island genetic differentiation (mean FST = 0.40) and relationships between islands are associated with their arrangement in geographical space; genetic distance is correlated with geographical distance and the genetic arrangement of islands is associated with longitude. The arrangement of islands as indicated by variation in body and skull metrics is also associated with their geographical positions, and the metric and genetic measures are themselves associated. While other taxa in the region have shown genetic‐geographical concordances, R. affinis is the only one that displays concordant patterns in metrical features. These patterns in biological diversity are interpreted as arising from the sequential island population structure and clines in key biogeographic gradients.
Geography of Pinus elliottii Engelm. and Pinus palustris Mill. leaf life‐spans in the southeastern U.S.A.
Authors: Holder Curtis D. 
Published: March 2003

AbstractAim Past studies have investigated differences in leaf life‐spans between deciduous and evergreen species. Environmental controls such as light, temperature, and nutrient and moisture availability explain differences in leaf life‐spans between species. This study examined intraspecific leaf life‐spans across climate and nutrient gradients within the geographical range of Pinus palustris Engelm (longleaf pine) and Pinus elliottii Mill. (slash pine).Location Five study areas in the southeastern United States were selected along the north–south geographical range of Pinus elliottii and Pinus palustris.Methods Leaf life‐span was calculated based on stand inventories and annual litterfall totals for each site, and allometric relationships between d.b.h. and foliar biomass.Results Leaf life‐span of P. elliottii ranged from 1.28 to 1.95 years between sites. Leaf life‐span of P.palustris varied by nearly a factor of 5 between the study site with the lowest and highest value (0.58–2.49 years).
anova indicated that leaf life‐spans of P. elliottii were not significantly different among sites. In contrast,
anova indicated a significant difference for P. palustris leaf life‐spans among sites (P < 0.05). The Tukey multiple comparisons tests showed that 2 study areas were the only pair of P. palustris sites with a significant difference in leaf life‐spans.Main conclusions The geographical variation in leaf life‐spans between two species illustrates the different phenotypic responses to environmental controls. The variation in leaf life‐spans by individuals of P. palustris across a geographical range illustrated in this study suggests that P. palustris may exhibit a greater phenotypic plasticity than P. elliottii.
Determinants of the northern and southern range limits of a warbler
Authors: Gross Sean J. , Price Trevor D. 
Published: March 2003

AbstractAimTo understand the determinants of range limits by studying the behaviour and ecology of a single species (the Hume’s leaf warbler, Phylloscopus humei) at both its northern and southern range limits.LocationsNorth‐west India (Himachal Pradesh) and central India (Maharashtra).MethodsWe worked at seven locations primarily in the winter of 1997–98. Five locations spanned the northern range limit of the species and two were close to the southern range limit. We censused arthropod and bird abundance (including both the Hume’s leaf warbler and other ecologically similar species) at each site. We also studied the foraging behaviour of the common warbler species.ResultsAcross the whole range of P. humei the abundance of arthropods is tightly correlated with the abundance of all warbler species. The northern range limit of P. humei coincides with the disappearance of arthropod food from its habitat (tree crowns), which is attributed to leaf loss associated with cold temperatures. Two closely related species, P. proregulus and Seicercus xanthoschistos have a northerly range limit beyond that of P. humei. They occupy the understory, which retains leaves and arthropods further north than do the tree crowns. The southern range limit of P. humei is associated with high food levels in its habitat, but also increasing numbers of a potential competitor, P. trochiloides, which is very similar in habits and also occupies the tree crowns, but is about 40% heavier. We attribute the decline of P. humei in the south to competition from P. trochiloides. Because food levels are high in the south, the mechanism of competition is likely to be interference, rather than exploitative.Main conclusionCompetition for food is likely involved in setting both the northern and southern range limits, but in very different ways. The results are discussed in the light of current theories for the way range limits are ultimately determined.