bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assemblage‐level responses of phyllostomid bats to tropical forest fragmentation: land‐bridge islands as a model system
Authors: Meyer Christoph F. J. , Kalko Elisabeth K. V. 
Published: July 2008

AbstractAim  Working within a system of high structural contrast between fragments and the surrounding matrix, we assessed patterns of species loss and changes in species composition of phyllostomid bats on artificial land‐bridge islands relative to mainland assemblages, and evaluated the responses of bats to forest edges. We further examined the relative influence of local‐scale characteristics (e.g. vegetation structure, island area) versus landscape attributes (e.g. forest cover, patch density) and the importance of spatial scale in determining phyllostomid species richness and composition on islands.Location  Islands in Gatún Lake and adjacent mainland peninsulas in the Barro Colorado Nature Monument, Panama.Methods  Bats were sampled over a 2‐year period on 11 islands as well as at forest‐edge and interior sites on adjacent mainland, resulting in > 8400 captures.Results  The islands harboured a less diverse and structurally simplified phyllostomid bat fauna. Islands far from the mainland were especially species‐poor. This decline in species richness was associated with compositional shifts towards assemblages strongly dominated by frugivores with good dispersal abilities. Members of other ensembles, most importantly gleaning animalivores, were much less common or absent. Although overall species composition was not significantly altered, species richness at continuous forest‐edge sites was significantly lower compared with that at interior sites. Distance from the mainland and amount of forest cover in the landscape were the best predictors of species richness and assemblage composition. Responses were scale‐dependent. At the local scale, species richness was independent of island area but was correlated positively with distance from the mainland. In contrast, area effects became more important at larger spatial scales, suggesting that many species use multiple fragments.Main conclusions  Our results underline the conservation value of small habitat remnants, which, even when embedded in a hostile matrix, can support a relatively diverse bat fauna, provided that there is a low degree of patch isolation and spatial proximity to larger tracts of continuous forest. Although the results at the assemblage level were inconclusive, we demonstrate that certain bat species and ensembles, particularly gleaning animalivores, exhibit high edge‐sensitivity. Our results point to habitat loss rather than changes in landscape configuration as the main process after isolation underlying phyllostomid bat responses, suggesting that conservation efforts should focus on habitat preservation instead of trying to minimize fragmentation per se at the expense of habitat amount.
Biodiversity of soft‐sediment benthic communities from Italian transitional waters
Authors: Munari Cristina , Mistri Michele 
Published: July 2008

AbstractAim  For conservation purposes, it is important to understand the forces that shape biodiversity in transitional waters (TWs) and to evaluate the effects of small‐scale latitudinal changes. To this end, we analysed data on soft‐sediment macroinvertebrates from nine Italian TWs in order to (1) investigate the structure and distribution of the benthic fauna and their relationships with environmental and geographical variables, and (2) examine species richness and β‐diversity at various spatial scales.Location  European Transition Waters Ecoregion 6.Methods  Using a data set collected along a 7° latitudinal cline between 45°28′ N and 39°56′ N, we used Spearman’s rank correlation analysis to evaluate the relationships between species richness and both environmental and geographical variables, and linear regression analysis to show the relationships between α‐, β‐ and γ‐diversity. Three measures were used to assess β‐diversity: Whittaker’s βW, and two similarity indices, namely the Bray‐Curtis similarity index and Δs. Using multivariate analyses, we determined the similarity in composition of the benthic community between sites and compared the biotic ordination with abiotic (geographical and environmental) characteristics.Results  Two hundred and sixty‐eight species were recorded from 46 sites. Of these, 53.4% were restricted to one TW. Annelida was the dominant taxonomic group, followed by Crustacea and Mollusca. The α‐diversity was highly variable (5–87 species) and was correlated with latitude. The γ‐diversity, measured at the TW scale, was correlated significantly with α‐diversity. The β‐diversity increased with spatial scale and habitat heterogeneity. In the community pattern identified by multivariate analysis, TWs were segregated by latitude and biogeography, and this reflected different climatic conditions.Main conclusions  We found that α‐diversity increased when moving from higher to lower latitudes, and that it depended on both regional and local factors. In addition, we detected latitudinal variations in the extent of regional influence on local species richness. The observed distribution pattern of TW faunas depended mostly on climate type. We suggest that the distribution of annelidan species could be used as a proxy for assessing general community patterns for Italian TWs.
Distribution patterns of land snails in Ugandan rain forests support the existence of Pleistocene forest refugia
Authors: Wronski Torsten , Hausdorf Bernhard 
Published: July 2008

AbstractAim We investigated whether the biogeographical patterns expected if the East African fauna was affected by cycles of contraction to refugia and expansion of ranges, as has been previously hypothesized, can be found in the land snail fauna of rain forests in Uganda.Location The Albertine Rift region and the Lake Victoria forest belt in Uganda.Methods Snails and slugs were sampled in 60 plots in 13 rain forests, and small species were extracted from 5‐L leaf litter samples. Relative species richness was calculated by rarefaction. The influence of putative determinants of species richness was examined by bivariate correlation and multiple regression. Clustering and nestedness were tested by Monte Carlo simulations with a null model that considers the range size distribution, the species richness distribution of the forests, and the spatial autocorrelation of the occurrences of each species. Biotic elements were determined by model‐based Gaussian clustering.Results A total of 169 land snail species were recorded from 13 Ugandan rain forests. Relative species richness increases with rainfall and altitude, and decreases with evaporation and distance from the putative East Congolian refugia. Mean annual rainfall and distance from the putative East Congolian refugia were included in the best multiple regression model. The distribution areas of the Ugandan land snails are significantly clustered. Two montane, two lowland and a northern biotic element were found. The mean range extension increases with increasing distance from the putative East Congolian refugia. Moreover, the ranges of the Ugandan land snails are significantly nested. The centre of the sets of nested subsets is in the Virunga Mountains, close to the putative East Congolian refugia.Main conclusions The decrease of diversity with increasing distance from the putative East Congolian refugia, the clustering and nestedness of ranges, and the range size increase with increasing distance from the refugia indicate that the East African land snail fauna was affected by cycles of contraction to refugia and expansion of ranges. The significant clustering and nestedness cannot be explained by current environmental conditions. Given the environmental history, it can be supposed that the lowland elements expanded post‐glacially, whereas the ranges of the montane species are probably currently contracting.
Phylogeography of the pallid kangaroo mouse,Microdipodops pallidus: a sand‐obligate endemic of the Great Basin, western North America
Authors: Hafner John C. , Upham Nathan S. , Reddington Emily , Torres Candice W. 
Published: July 2008

AbstractAim Kangaroo mice, genusMicrodipodopsMerriam, are endemic to the Great Basin and include two species:M. pallidusMerriam andM. megacephalusMerriam. The pallid kangaroo mouse,M. pallidus, is a sand‐obligate desert rodent. Our principal intent is to identify its current geographical distribution and to formulate a phylogeographical hypothesis for this taxon. In addition, we test for orientation patterns in haplotype sharing for evidence of past episodes of movement and gene flow.Location The Great Basin Desert region of western North America, especially the sandy habitats of the Lahontan Trough and those in south‐central Nevada.Methods Mitochondrial DNA sequence data from portions of three genes (16S ribosomal RNA, cytochromeb, and transfer RNA for glutamic acid) were obtained from 98 individuals ofM. pallidusrepresenting 27 general localities sampled throughout its geographical range. Molecular sequence data were analysed using neighbour‐joining, maximum‐parsimony, maximum‐likelihood and Bayesian methods of phylogenetic inference. Directional analysis of phylogeographical patterns, a novel method, was used to examine angular measurements of haplotype sharing between pairs of localities to detect and quantify historical events pertaining to movement patterns and gene flow.Results Collecting activities showed thatM. pallidusis a rather rare rodent (mean trapping success was 2.88%), and its distribution has changed little from that determined three‐quarters of a century ago. Two principal phylogroups, distributed as eastern and western moieties, are evident from the phylogenetic analyses (mean sequence divergence for cytochromebisc. 8%). The western clade shows little phylogenetic structure and seems to represent a large polytomy. In the eastern clade, however, three subgroups are recognized. Nine of the 42 unique composite haplotypes are present at two or more localities and are used for the orientation analyses. Axial data from haplotype sharing between pairwise localities show significant, non‐random angular patterns: a north‐west to south‐east orientation in the western clade, and a north‐east to south‐west directional pattern in the eastern clade.Main conclusions The geographical range ofM. pallidusseems to be remarkably stable in historical times and does not show a northward (or elevationally upward) movement trend, as has been reported for some other kinds of organism in response to global climate change. The eastern and western clades are likely to represent morphologically cryptic species. Estimated times of divergence of the principal clades ofM. pallidus(4.38 Ma) and betweenM. pallidusandM. megacephalus(8.1 Ma; data from a related study) indicate that kangaroo mice diverged much earlier than thought previously. The phylogeographical patterns described here may serve as a model for other sand‐obligate members of the Great Basin Desert biota.
Red herring or low illumination? The peninsula effect revisited
Authors: Jenkins David G. , Rinne Debra 
Published: July 2008

AbstractAim The peninsula effect is the prediction that the number of species declines from a peninsula's base to its tip. We evaluated evidence for and against the peninsula effect, and conducted a field study designed to test alternative hypotheses for that effect.Location The Florida peninsula, USA.Methods First, we critically reviewed the accumulated literature on peninsula effects; second, we sampled microcrustaceans in palustrine wetlands on the ridges of peninsular Florida. Site selection in our field study accounted for historical effects and partially controlled for habitat effects. Statistical analyses further accounted for habitat effects, leaving peninsular geometry as the remaining causative mechanism for residual variation in species richness regression analyses.Results Our literature review found mixed evidence (49% of cases) for a peninsula effect. However, most study designs did not control for alternative hypotheses, most comparisons of alternative hypotheses were qualitative, and most studies focused on vertebrate animals. Our field study found that freshwater microcrustaceans inhabiting isolated wetlands on Florida’s peninsular ridges do not exhibit a peninsula effect. Essentially, no variation in microcrustacean species richness could be attributed to peninsular geometry, but 82.5% of variation in species richness was attributed to habitat and sampling effort.Main conclusions Although our research results support the ‘red herring’ label for the peninsula effect, our literature review leads us to argue that more illumination (in the form of study design and quantitative analysis) is needed if mechanisms causing the peninsula effect hypothesis are to be resolved. Future studies of peninsula effects need to control for alternative causative hypotheses (geometry, habitat or history) in study design, and compare quantitatively the effects of hypothesized mechanisms on peninsular diversity patterns. Additionally, studies of taxa other than vertebrate animals need to be conducted for generality. Our study may serve as an example of such an approach.
Definition of grassland biomes from phytoliths in West Africa
Authors: Bremond Laurent , Alexandre Anne , Peyron Odile , Guiot Joël 
Published: July 2008

AbstractAim  In order to enhance the effectiveness of comparisons between modelled and empirical data for present and past vegetation, it is important to improve the characterization of tropical grass‐dominated biomes reconstructed from fossil tracers. This study presents a method for assigning phytolith assemblages to tropical grass‐dominated biomes, with the objective of offering a new tool for combining pollen and phytolith data in the reconstruction of tropical biomes.Location  The West African latitudinal transect studied here extends from 12° N (southern Senegal) to 23° N (southern Mauritania), passing through the Guinean, Sudanian, Sahelian and Saharan bioclimatic zones.Methods  Modern phytolith assemblages were extracted from 59 soil surface samples taken throughout the study area and allocated, a priori, to three current biomes: (1) desert C4 grassland, (2) short grass savanna, and (3) tall grass savanna. Five out of nine phytolith types identified were used as predictors in a discriminant analysis (with calibration and validation steps) for assigning phytolith assemblages to biomes. In addition, 74 modern pollen spectra from the West African transect, acquired from the African Pollen Database (http://medias.obs‐mip.fr/apd), were processed by the biomization method. This mathematical procedure involves assigning palynological taxa to one or more plant functional types, which represent broad classes of plants. The plant functional types, in turn, are combined to define biomes following a specific set of algorithms and rules. The resulting maps of the phytolith biomes thus derived were compared with maps of pollen biomes and of contemporary ecosystem classes.Results  In the calibration and validation steps, 91.5% and up to 83%, respectively, of the phytolith samples were assigned to the correct biome. The short grass savanna and tall grass savanna biomes were assigned with similar accuracy by both the phytolith and pollen biomization methods, but the phytolith method gave substantially superior results for the desert C4 grassland biome, providing seven out of seven correct assignments, compared with just one out of four by pollen biomization. Comparisons between an existing ecosystem map and the maps created from phytolith estimation showed close correspondence for desert C4 grassland, short grass savanna and tall grass savanna, the latter providing correct assignments in 88, 62 and 91% of cases, respectively.Main conclusions  The phytolith discriminant analysis method presented here accurately estimates three C4 grass‐dominated biomes that are widespread in West Africa. Complementarities between the phytolith method and pollen biomization are highlighted. Combining complementary phytolith and pollen data would provide more accurate assignments of C4 grass‐dominated biomes than pollen biomization alone.
Does the varied use of NSAIDs explain the differences in the risk of myocardial infarction?
Authors: Van Staa T.‐P. , Rietbrock S. , Setakis E. , Leufkens H. G. M. 
Published: July 2008

Abstract.Objective.  To investigate the risk of myocardial infarction (MI) with diclofenac, ibuprofen and naproxen, taking into account the exposure patterns.Design.  Retrospective cohort study using the General Practice Research Database.Setting.  UK primary care.Subjects.  Patients aged 40+ years prescribed a traditional nonsteroidal anti‐inflammatory drug (NSAID). The control cohort was frequency matched by disease risk score.Intervention.  Observational comparisons of MI rates.Results.  The study included 729294 NSAID users and 443047 controls. The relative rate (RR) for MI increased with cumulative and daily dose (RR = 1.05 with 0–4 prior prescriptions and RR = 1.49 with 30+; RR = 1.05 with daily dose of <1200 mg ibuprofen and RR = 1.96 with dose of ≥2400 mg per day; for diclofenac, the RR was 1.13 with <150 mg per day and 2.03 with ≥300 mg per day). Diclofenac users had higher risks of MI (RR = 1.21) than ibuprofen (RR = 1.04) or naproxen (RR = 1.03) users, but exposure varied between these drugs. Taking into account these exposure differences, it was found that the risk of MI was comparable in current and past long‐term users. The patterns of hazard rates (i.e. absolute risks) of MI were similar in patients using ibuprofen, diclofenac or naproxen with similar history of NSAID use. There was no statistical difference between ibuprofen, diclofenac and ibuprofen in the linear trends for cumulative dose or daily dose.Conclusions.  Long‐term users of traditional NSAIDs have an increased risk of MI that is probably explained by the underlying disease severity. Most of the differences in MI risk between diclofenac, ibuprofen or naproxen may be explained by their varied use.
Recombination of synthetic oligonucleotides with prokaryotic chromosomes: substrate requirements of the Escherichia coli/λRed and Sulfolobus acidocaldarius recombination systems
Authors: Grogan Dennis W. , Stengel Kristy R. 
Published: July 2008

SummaryIn order to reveal functional properties of recombination involving short ssDNAs in hyperthermophilic archaea, we evaluated oligonucleotide‐mediated transformation (OMT) in Sulfolobus acidocaldarius and Escherichia coli as a function of the molecular properties of the ssDNA substrates. Unmodified ssDNAs as short as 20–22 nt yielded recombinants in both organisms, as did longer DNAs forming as few as 2–5 base pairs on one side of the genomic mutation. The two OMT systems showed similar responses to certain end modifications of the oligonucleotides, but E. coli was found to require a 5′ phosphate on 5′‐limited ssDNA whereas this requirement was not evident in S. acidocaldarius. The ability of both E. coli and S. acidocaldarius to incorporate short, mismatched ssDNAs into their genomes raises questions about the biological significance of this capability, including its phylogenetic distribution among microorganisms and its impact on genome stability. These questions seem particularly relevant for S. acidocaldarius, as this archaeon has natural competence for OMT, encodes no MutSL homologues and thrives under environmental conditions that accelerate DNA decomposition.
The periplasmic regulator ExoR inhibits ExoS/ChvI two‐component signalling in Sinorhizobium meliloti
Authors: Chen Esther J. , Sabio Erich A. , Long Sharon R. 
Published: July 2008

Summary Sinorhizobium meliloti requires ExoS/ChvI two‐component signalling to establish a nitrogen‐fixing symbiosis with legume hosts. The importance of ExoS/ChvI signalling in microbe–host interactions is underscored by the requirement of ExoS/ChvI orthologues for virulence of the related α‐proteobacteria Agrobacterium tumefaciens and Brucella abortus. In S. meliloti, ExoS/ChvI is a key regulator of gene expression for exopolysaccharide synthesis, biofilm formation, motility, nutrient utilization and free‐living viability. Previously, we showed that the novel conserved regulator ExoR interacts genetically with both ExoS and ChvI, and localizes to the periplasm of S. meliloti. Here, we show that ExoR physically associates with ExoS and that this association is important for regulating ExoS/ChvI signalling. We have identified point mutations in the Sel1‐like repeat region of ExoR that disrupt binding to ExoS and cause a dramatic increase in ExoS/ChvI‐dependent gene expression. Furthermore, we have found that physical interaction with ExoS stabilizes the ExoR protein. Together, our results indicate that ExoR binds to ExoS in the periplasm of S. meliloti to inhibit ExoS/ChvI activity, and that ExoR represents a novel periplasmic inhibitor of two‐component signalling.
Diagenesis of plattenkalk: examples from the Solnhofen area (Upper Jurassic, southern Germany)
Authors: MUNNECKE AXEL , WESTPHAL HILDEGARD , KÖLBL‐EBERT MARTINA 
Published: July 2008

AbstractThe Upper Jurassic (Tithonian) plattenkalk successions in the Solnhofen/Eichstätt area consist of alternations of thin‐bedded, laminated, fine‐grained, very pure limestones (so‐called ‘flinz beds’) and softer interlayers with slightly lower carbonate contents that are also laminated and show a foliaceous weathering appearance (‘fäule beds’). These successions are world famous for their exceptionally well‐preserved fossils. In contrast to the well‐studied wealth of fossils, little is known about the origin and diagenesis of the host rock. The reason for this discrepancy might lay in the monotonous appearance of these fine‐grained mudstones that require electron microscopical examination. Study of samples from the Solnhofen–Eichstädt area implies that flinz and fäule beds have undergone differential diagenesis. The ultrastructure of the flinz beds is characterized by interlocking microspar crystals, whereas the fäule beds show smaller and less interlocking crystals. The ratios of diagenetically inert trace elements lack clear differences between the two interlayered lithologies. While most authors agree that the flinz–fäule rhythm reflects rhythmically changing environmental conditions, primary rhythms can be taken as proven only where statistically significant differences in diagenetically resistant proxies are found. The absence of clear primary differences between flinz and fäule beds, however, leaves the question of primary differences unsolved. It is concluded that diagenesis has had a strong influence on the genesis of the lithological rhythm, and that any primary rhythm underlying the diagenetically mature rhythm is less clear than generally assumed.
New insights of HLA class I association to Behçet’s disease in Portuguese patients
Authors: Bettencourt A. , Pereira C. , Carvalho L. , Carvalho C. , Patto J. V. , Bastos M. , Silva A. M. , Barros R. , Vasconcelos C. , Paiva P. , Costa L. , Costa P. P. , Mendonça D. , Correia J. , Silva B. M. 
Published: July 2008

AbstractHuman leukocyte antigen (HLA)‐B*51 is a well‐known genetic factor associated with Behçet’s disease (BD). To analyse the influence of HLA‐B*51 and other HLA class I alleles in BD susceptibility in a Portuguese population and its association with disease severity, we studied 78 BD patients and 208 healthy controls. The patients were classified into two severity groups as described by Gul et al. As expected, a higher frequency of HLA‐B*51 was found. The frequency of HLA‐Cw*16 alleles was significantly higher in patients. Regarding severity, HLA‐B*27 frequency was higher in the severe group compared with controls and with the mild group. Thus, HLA‐B*51 and HLA‐Cw*16 seem to confer susceptibility to BD in this patients. HLA‐B*27 may be important as a prognostic factor.