bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feedbacks between nutrient cycling and vegetation predict plant species coexistence and invasion
Authors: Miki Takeshi , Kondoh Michio 
Published: March 2003

AbstractTo investigate the role of species‐specific litter decomposability in determining plant community structure, we constructed a theoretical model of the codevelopmental dynamics of soil and vegetation. This model incorporates feedback between vegetation and soil. Vegetation changes the nutrient conditions of soil by affecting mineralization processes; soil, in turn, has an impact on plant community structure. The model shows that species‐level traits (decomposability, reproductive and competitive abilities) determine whether litter feedback effects are positive or negative. The feedback determines community‐level properties, such as species composition and community stability against invasion. The model predicts that positive feedback may generate multiple alternative steady states of the plant community, which differ in species richness or community composition. In such cases, the realized state is determined by initial abundance of co‐occurring species. Further, the model shows that the importance of species‐level traits depends on environmental conditions such as system fertility.
From parasitism to mutualism: partner control in asymmetric interactions
Authors: Johnstone Rufus A. , Bshary Redouan 
Published: March 2003

AbstractIntraspecific cooperation and interspecific mutualism often feature a marked asymmetry in the scope for exploitation. Cooperation may nevertheless persist despite one‐sided opportunities for cheating, provided that the partner vulnerable to exploitation has sufficient control over the duration of interaction. Here we develop a simple, game theoretical model of this form of partner control. We show that as a victim's ability to terminate an encounter increases, selection can favour reduced exploitation, resulting in a switch from parasitism to mutualism. For a given level of control, exploitation is likely to be less intense and the interaction to last longer when there are greater mutualistic benefits to be gained, and when the benefits of cheating are lower relative to the costs inflicted on the victim. Observations of interactions between cleaner‐fish and non‐predatory species of client are shown to match these predictions.
Island theory, matrix effects and species richness patterns in habitat fragments
Authors: Cook William M. , Lane Kurt T , Foster Bryan L. , Holt Robert D. 
Published: March 2003

AbstractIsland biogeography theory, created initially to study diversity patterns on islands, is often applied to habitat fragments. A key but largely untested assumption of this application of theory is that landscape matrix species composition is non‐overlapping with that of the islands. We tested this assumption in successional old field patches in a closely mowed matrix, and because our patches are appropriately viewed as sets of contiguous habitat units we studied patterns of species richness per unit area. Previous studies at our site did not find that diversity patterns on patch ‘islands’ conformed to predictions of island biogeography theory. Our results indicate that when matrix species are removed from the patch samples, diversity patterns conform better to theory. We suggest that classical island theory remains an appropriate tool to study diversity patterns in fragmented habitats, but that allowances should be made for spill‐over colonization of ‘islands’ from the ‘sea’.
Reductions in grassland species evenness increase dicot seedling invasion and spittle bug infestation
Authors: Wilsey Brian J. , Polley H. Wayne 
Published: March 2003

AbstractPrevious experiments that tested whether diverse plant communities have lower invasibility have all varied species richness. We experimentally varied evenness of four grassland species (three grasses and one forb) by planting a field experiment in Texas, and monitored the number of unplanted dicot and monocot species that invaded plots for two growing seasons. By varying evenness, we eliminated any sampling effect in our diversity treatment, because all plots contained the same plant species. Experimentally reducing evenness led to a greater number of dicot invaders, which emerged in plots throughout the growing season, but had less of an effect on monocot invaders, which emerged in flushes when experimental plants were semi‐dormant. Frequency of Solidago canadensis (altissima) stems with spittle bugs significantly increased with reductions in evenness during the first year, apparently because the greater number of Solidago stems in high evenness plots diluted the spittle‐bug effect. These results support the view that higher diversity plant communities are more resistant to dicot invaders and insect herbivores.
Threatened and endemic species: are they good indicators of patterns of biodiversity on a national scale?
Authors: Bonn Aletta , Rodrigues Ana S. L. , Gaston Kevin J. 
Published: March 2003

AbstractEndemic and/or threatened species are often targeted to set conservation priorities. It is tempting to assume that a reserve network focusing on these species will be an effective umbrella for overall species richness of a country. For South Africa and Lesotho we tested whether complementary networks selected for threatened and/or endemic bird species satisfactorily represent all bird species, both in terms of capturing areas where other species are present or areas where they are more abundant (and, presumably, more viable). We found that areas selected for threatened and endemic species perform considerably better than areas selected at random. However, they do not guarantee the representation of overall bird species diversity, particularly not in peak abundance locations. Although nationally threatened and endemic species are important conservation targets, our results indicate that reserve networks focusing solely on these species may not be sufficient to preserve overall species diversity in a country.
Insect perception of ambient ultraviolet‐B radiation
Authors: Mazza Carlos A. , Izaguirre Miriam M. , Zavala Jorge , Scopel Ana L. , Ballaré Carlos L. 
Published: March 2003

AbstractSolar ultraviolet‐B radiation (UV‐B, 290–315 nm) has a strong influence on the interactions between plants and animal consumers. Field studies in various ecosystems have shown that the intensity of insect herbivory increases when the UV‐B spectral band of solar radiation is experimentally attenuated using filters. This effect of UV‐B on insect herbivory has been attributed to UV‐B‐induced changes in the characteristics of plant tissues, and to direct damaging effects of UV‐B photons on the animals. We tested for effects of UV‐B radiation on insect behaviour using field experiments with the thrips Caliothrips phaseoli. When placed in a ‘choice’ tunnel under natural daylight, these insects showed a clear preference for low‐UV‐B environments, and this preference could not be accounted for by differences between environments in total irradiance. These results provide the first evidence of ambient UV‐B photoperception in an insect, challenging the idea that animals are unable to detect variations in the narrow UV‐B component of solar radiation.
Are three‐dimensional spider webs defensive adaptations?
Authors: Blackledge Todd A. , Coddington Jonathan A. , Gillespie Rosemary G. 
Published: March 2003

AbstractSpider webs result from complex behaviours that have evolved under many selective pressures. Webs have been primarily considered to be foraging adaptations, neglecting the potential role of predation risk in the evolution of web architecture. The ecological success of spiders has been attributed to key innovations in how spiders use silk to capture prey, especially the invention of chemically adhesive aerial two‐dimensional orb webs. However, araneoid sheet web weavers transformed the orb architecture into three‐dimensional webs and are the dominant group of aerial web‐building spiders world‐wide, both in numbers and described species diversity. We argue that mud‐dauber wasps are major predators of orbicularian spiders, and exert a directional selective pressure to construct three‐dimensional webs such that three‐dimensional webs are partly defensive innovations. Furthermore, patterns of diversification suggest that escape from wasp predators may have facilitated diversification of three‐dimensional web‐building spiders.
The area‐independent effects of habitat complexity on biodiversity vary between regions
Authors: Johnson Mark P. , Frost Natalie J. , Mosley Matthew W. J. , Roberts Malcolm F. , Hawkins Stephen J. 
Published: March 2003

AbstractPotential explanatory variables often co‐vary in studies of species richness. Where topography varies within a survey it is difficult to separate area and habitat‐diversity effects. Topographically complex surfaces may contain more species due to increased habitat diversity or as a result of increased area per se. Fractal geometry can be used to adjust species richness estimates to control for increases in area on complex surfaces. Application of fractal techniques to a survey of rocky shores demonstrated an unambiguous area‐independent effect of topography on species richness in the Isle of Man. In contrast, variation in species richness in south‐west England reflected surface availability alone. Multivariate tests and variation in limpet abundances also demonstrated regional variation in the area‐independent effects of topography. Community composition did not vary with increasing surface complexity in south‐west England. These results suggest large‐scale gradients in the effects of heterogeneity on community processes or demography.
Invasive California poppies (Eschscholzia californicaCham.) grow larger than native individuals under reduced competition
Authors: Leger Elizabeth A. , Rice Kevin J. 
Published: March 2003

AbstractInvasive plants can be larger and more fecund in their invasive range than in their native range, although it is unknown how often this is a result of a genetically controlled shift in traits, a plastic response to a favourable environment, or a combination thereof. Here we present data from common garden experiments that compare the size and fecundity of native and invasive California poppies,Eschscholzia californicaCham. Individuals from 20 populations, half from California (native) and half from Chile (invasive), were grown both with and without competition from other plants in a container experiment and at two field locations. There were no differences in survival between native and invasive plants at any location. We found significant increases in size and fecundity in invasive populations at two of three locations when poppies were grown without competition from other plants. Our results indicate that genetic shifts in traits have occurred in invasive populations, and that the invasive plants are better at maximizing growth and reproduction in open environments.
Could Bt transgenic crops have nutritionally favourable effects on resistant insects?
Authors: Sayyed Ali H. , Cerda Hugo , Wright Denis J. 
Published: March 2003

AbstractWe present an idea that larvae of some Bacillus thuringiensis (Bt ) resistant populations of the diamondback moth, Plutella xylostella (L.), may be able to use Cry1Ac toxin derived from Bt as a supplementary food protein. Bt transgenic crops could therefore have unanticipated nutritionally favourable effects, increasing the fitness of resistant populations. This idea is discussed in the context of the evolution of resistance to Bt transgenic crops.
Optimization of an oligonucleotide microchip for microbial identification studies: a non‐equilibrium dissociation approach
Authors: Liu Wen‐Tso , Mirzabekov Andrei D. , Stahl David A. 
Published: March 2003

SummaryThe utility of a high‐density oligonucleotide microarray (microchip) for identifying strains of five closely related bacilli (Bacillus anthracis, Bacillus cereus, Bacillus mycoides, Bacillus medusa and Bacillus subtilis) was demonstrated using an approach that compares the non‐equilibrium dissociation rates (‘melting curves’) of all probe–target duplexes simultaneously. For this study, a hierarchical set of 30 oligonucleotide probes targeting the 16S ribosomal RNA of these bacilli at multiple levels of specificity (approximate taxonomic ranks of domain, kingdom, order, genus and species) was designed and immobilized in a high‐density matrix of gel pads on a glass slide. Reproducible melting curves for probes with different levels of specificity were obtained using an optimized salt concentration. Clear discrimination between perfect match (PM) and mismatch (MM) duplexes was achieved. By normalizing the signals to an internal standard (a universal probe), a more than twofold discrimination (> 2.4×) was achieved between PM and 1‐MM duplexes at the dissociation temperature at which 50% of the probe–target duplexes remained intact. This provided excellent differentiation among representatives of different Bacillus species, both individually and in mixtures of two or three. The overall pattern of hybridization derived from this hierarchical probe set also provided a clear ‘chip fingerprint’ for each of these closely related Bacillus species.
Community shifts in a seeded 3‐chlorobenzoate degrading membrane biofilm reactor: indications for involvement of in situ horizontal transfer of the clc‐element from inoculum to contaminant bacteria
Authors: Springael Dirk , Peys Kurt , Ryngaert Annemie , Roy Sandra Van , Hooyberghs Liliane , Ravatn Roald , Heyndrickx Marc , Meer Jan‐Roelof van der , Vandecasteele Carlo , Mergeay Max , Diels Ludo 
Published: March 2003

Summary Pseudomonas putida BN210, carrying the self‐ transferable clc‐element encoding degradation of 3‐chlorobenzoate on the chromosome, was used as inoculum in different membrane biofilm reactors treating 3‐chlorobenzoate‐contaminated model wastewater. Analysis of the bacterial population in the effluent and in the biofilm showed the loss of BN210 beyond detection from the reactors and the appearance of several novel 3‐chlorobenzoate mineralizing bacteria mainly belonging to the β‐proteobacteria. In contrast, in non‐inoculated reactors, no 3‐chlorobenzoate degradation was observed and no 3‐chlorobenzoate degraders could be recovered. Southern blots hybridization of genomic DNA using clc‐element‐specific probes and FIGE analysis indicated the presence of the complete clc‐element in one or more copies in the isolates. Moreover, the isolates could transfer the clc genes to Ralstonia metallidu‐rans recipients. Two representative reactor isolates, Ralstonia sp. strains KP3 and KP9 demonstrated a higher growth rate on 3‐chlorobenzoate than strain BN210 in batch cultures. When BN210, KP3 and KP9 were simultaneously inoculated in a membrane reactor supplied with 3‐chlorobenzoate, strain KP3 outcompeted the two other strains and remained the major 3‐chlorobenzoate degrading population in the reactor. Our data suggest that in situ horizontal transfer of the clc‐element from the inoculum to contaminant bacteria in the reactors was involved in the establishment of novel 3‐chlorobenzoate degrading populations that were more competitive under the defined reactor conditions than the inoculum strain.
Persistence of Escherichia coli O157:H7 in soil and on plant roots
Authors: Gagliardi Joel V. , Karns Jeffrey S. 
Published: March 2003

SummarySoil microcosms were inoculated with Escherichia coli O157:H7 to test persistence in fallow soil, on roots of cover crops and in presence of manure. In fallow soils, E. coli O157:H7 persisted for 25–41 days, on rye roots for 47–96 days and on alfalfa roots, in a silt loam soil, for 92 days whereas on other legumes persistence ranged from 25–40 days, similar to fallow soil. Manure did not seem to affect the persistence of E. coli O157:H7 in these soils. Indigenous and manure‐applied coliform populations often decreased faster when E. coli O157:H7 was applied, indicating possible competition between microflora. Coliform populations in microcosms not inoculated with E. coli O157:H7 decreased more slowly or increased. Microbial community analyses showed little effect for E. coli O157:H7 inoculation or addition of manure. Microbial community metabolic activity was enhanced from rye roots after 14 days and by 63 days from alfalfa roots. Microbial community lactose utilization increased over time on rye roots in all soils and on alfalfa roots in a silt loam soil when E. coli O157:H7 was inoculated. Lactose utilization also increased for uninoculated rye roots, soil around rye roots and in some fallow soils. Our data suggest that clay increases persistence and activity of E. coli O157:H7 and other coliforms. In frozen soil stored for over 500 days, E. coli O157:H7 was viable in 37% of tested samples. In summary, E. coli O157:H7 persisted longer and activity was enhanced with some cover crops in these soils due to plant roots, the presence of clay and freezing.
Seasonal dynamics of particle‐associated and free‐living marine Proteobacteria in a salt marsh tidal creek as determined using fluorescence in situ hybridization
Authors: Dang Hongyue , Lovell Charles R. 
Published: March 2003

SummaryThe seasonal distributions of salt marsh free‐living and particle‐associated bacteria belonging to three subdivisions of the Proteobacteria were determined by fluorescence
in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM).
More than 66% (median = 78%) of total bacterial cells that were stainable
with the fluorescent DNA stain Yo‐Pro‐1 were also detected using the bacterial probe
EUB338. The α‐Proteobacteria, especially those from the marine
Rhodobacter group, were abundant on suspended particles and as free‐living
cells all year round. The marine Rhodobacter group constituted more than 25%
of the particle‐associated bacteria and more than 18% of the free‐living
bacteria. Probes specific for three subgroups within the marine Rhodobacter
group detected more than 49% of the total marine Rhodobacter group
cells. These subgroups displayed different seasonal dynamics. The marine Rhodobacter group is clearly a widespread, diverse and important bacterial lineage in bacterioplankton and particle‐associated assemblages in south‐eastern United States salt marshes at all times of the year.
Stratification and seasonal stability of diverse bacterial communities in a Pinus merkusii (pine) forest soil in central Java, Indonesia
Authors: Krave Agna S. , Lin Bin , Braster Martin , Laverman Anniet M. , Straalen Nico M. van , Röling Wilfred F. M. , Verseveld Henk W. van 
Published: March 2003

SummaryIn Java, Indonesia, many nutrient‐poor soils are intensively reforested with Pinus
merkusii (pine). Information on nutrient cycles and microorganisms involved in
these cycles will benefit the management of these important forests. Here, seasonal
effects on the stratification of bacterial community structure in the soil profile
of a tropical pine forest are described, and differences in bacterial communities
are related to chemical and physical soil parameters. Culture‐independent community
profiles of litter, fragmented litter and mineral soil layers were made by denaturing
gradient gel electrophoresis (DGGE) of 16S rDNA‐specific polymerase chain reaction
(PCR) fragments. The community profiles of the different soil layers clustered separately,
correlating with significant differences in organic matter content between the three
layers. The bacterial communities appeared to be stable during the wet season of
1998. The drought in 1997, caused by the El Niño climatic effect,
did not influence the bacterial communities in fragmentation and mineral soil, although
moisture content and other soil parameters were markedly lower than in the wet season.
However, communities in litter were influenced by drought. In the litter layer, the
moisture content was significantly lower than in the fragmentation and mineral layers
during the dry season. A clone library was made from a litter sample taken during
the wet season. Partial sequencing of 74 clones and linking the DGGE banding positions
of these clones to bands in the DGGE profile of the sample from which the clone library
was derived showed considerable bacterial diversity. Alpha‐proteobacteria (40.5%
of the clones, of which 57% belonged to the Rhizobium–Agrobacterium group) and high‐G+C content, Gram‐positive bacteria (36.5%) dominated the clone library.
Picobenthic cyanobacterial populations revealed by 16S rRNA‐targeted in situ hybridization
Authors: Abed Raeid M. M. , Schönhuber Wilhelm , Amann Rudolf , Garcia‐Pichel Ferran 
Published: March 2003

SummaryWe report on the morphological identification of a population of benthic cyanobacteria from microbial mats, known previously only from molecular analyses of field samples, based on the retrieval of environmental 16S rRNA sequences. We used in situ hybridization with horseradish peroxidase‐labelled oligonucleotide probes designed to target the 16S rRNA of our unidentified population. Two probes were designed and checked for target binding ability and specificity using membrane hybridization against electroblotted bands from a denaturant gradient gel electrophoresis (DGGE) fingerprint of 16S rDNA gene fragments from the original cyanobacterial community. Under in situ hybridization, these probes bound specifically to extremely small, unicellular, colony‐forming cyanobacteria, 0.75–1 μm in diameter, which were embedded in abundant mucilaginous investments. We propose the term picobenthos, by analogy with picoplankton, to describe those unicellular benthic microbes around or less than 1 μm in diameter. Although picoplanktonic cyanobacteria are abundant in ocean and freshwaters, picobenthic (<1 μm) unicellular cyanobacteria are not typically recognized as a major component of microbial mats. The small size and low levels of photopigment autofluorescence from these cells probably rendered them cryptic or indistinguishable from heterotrophic bacteria in routine microscopic observations. It is not known how widespread picobenthic cyanobacteria may be in other environments.
nifH gene diversity in the bacterial community associated with the rhizosphere of Molinia coerulea, an oligonitrophilic perennial grass
Authors: Hamelin Jérôme , Fromin Nathalie , Tarnawski Sonia , Teyssier‐Cuvelle Sylvie , Aragno Michel 
Published: March 2003

AbstractRhizosphere associative dinitrogen fixation could be a valuable source of nitrogen in many nitrogen limited natural ecosystems, such as the rhizosphere of Molinia coerulea, a hemicryptophytic perennial grass naturally occurring in contrasted oligonitrophilic soils. The diversity of the dinitrogen‐fixing bacteria associated with this environment was assessed by a cloning–sequencing approach on the nifH gene directly amplified from environmental DNA extracts. Seventy‐seven randomly picked clones were analysed. One type of NifH sequence was dominant in both roots and surrounding soil, and represented 56% of all retrieved sequences. This cluster included previously described environmental clones and did not contain any NifH sequences similar to cultivated diazotrophs. The predominance of few NifH sequence types in the roots and the rhizosphere of Molinia coerulea indicate that the plant environment mediates a favourable niche for such dinitrogen‐fixing bacteria.