bluuebunny/crossref_metadata_2025_split huggingface dataset:
Climatic variation and the distribution of an amphibian polyploid complex
Authors: OTTO CLINT R. V. , SNODGRASS JOEL W. , FORESTER DON C. , MITCHELL JOSEPH C. , MILLER ROBERT W. 
Published: September 2007

Summary

The establishment of polyploid populations involves the persistence and growth of the polyploid in the presence of the progenitor species. Although there have been a number of animal polyploid species documented, relatively few inquiries have been made into the large‐scale mechanisms of polyploid establishment in animal groups. Herein we investigate the influence of regional climatic conditions on the distributional patterns of a diploid–tetraploid species pair of gray treefrogs, Hyla chrysoscelis and H. versicolor (Anura: Hylidae) in the mid‐Atlantic region of eastern North America.
Calling surveys at breeding sites were used to document the distribution of each species. Twelve climatic models and one elevation model were generated to predict climatic and elevation values for gray treefrog breeding sites. A canonical analysis of discriminants was used to describe relationships between climatic variables, elevation and the distribution of H. chrysoscelis and H. versicolor.
There was a strong correlation between several climatic variables, elevation and the distribution of the gray treefrog complex. Specifically, the tetraploid species almost exclusively occupied areas of higher elevation, where climatic conditions were relatively severe (colder, drier, greater annual variation). In contrast, the diploid species was restricted to lower elevations, where climatic conditions were warmer, wetter and exhibited less annual variation.
Clusters of syntopic sites were associated with areas of high variation in annual temperature and precipitation during the breeding season.
Our data suggest that large‐scale climatic conditions have played a role in the establishment of the polyploid H. versicolor in at least some portions of its range. The occurrence of the polyploid and absence of the progenitor in colder, drier and more varied environments suggests the polyploid may posses a tolerance of severe environmental conditions that is not possessed by the diploid progenitor.
Our findings support the hypothesis that increased tolerance to severe environmental conditions is a plausible mechanism of polyploid establishment.
Thermal tolerance and geographical range size in theAgabus brunneusgroup of European diving beetles (Coleoptera: Dytiscidae)
Authors: Calosi P. , Bilton D. T. , Spicer J. I. , Atfield A. 
Published: September 2007

AbstractAim Within clades, most taxa are rare, whilst few are common, a general pattern for which the causes remain poorly understood. Here we investigate the relationship between thermal performance (tolerance and acclimation ability) and the size of a species’ geographical range for an assemblage of four ecologically similar European diving beetles (theAgabus brunneusgroup) to examine whether thermal physiology relates to latitudinal range extent, and whether Brown’s hypothesis and the environmental variability hypothesis apply to these taxa.Location Europe.Methods In order to determine the species tolerances to either low or high temperatures we measured the lethal thermal limits of adults, previously acclimated at one of two temperatures, by means of thermal ramping experiments (± 1°C min−1). These measures of upper and lower thermal tolerances (UTT and LTT respectively) were then used to estimate each species’ thermal tolerance range, as total thermal tolerance polygons and marginal UTT and LTT thermal polygons.Results Overall, widespread species have higher UTTs and lower LTTs than restricted ones. Mean upper lethal limits of theAgabus brunneusgroup (43 to 46°C), are similar to those of insects living at similar latitudes, whilst mean lower lethal limits (−6 to −9°C) are relatively high, suggesting that this group is not particularly cold‐hardy compared with other mid‐temperate‐latitude insects. Widespread species possess the largest thermal tolerance ranges and have a relatively symmetrical tolerance to both high and low temperatures, when compared with range‐restricted relatives. Over the temperature range employed, adults did not acclimate to either high or low temperatures, contrasting with many insect groups, and suggesting that physiological plasticity has a limited role in shaping distribution.Main conclusions Absolute thermal niche appears to be a good predictor of latitudinal range, supporting both Brown’s hypothesis and the environmental variability hypothesis. Restricted‐range species may be more susceptible to the direct effect of climate change than widespread species, notwithstanding the possibility that even ‘thermally‐hardy’, widespread species may be influenced by the indirect effects of climate change such as reduction in habitat availability in Mediterranean areas.
How few whales were there after whaling? Inference from contemporary mtDNA diversity
Authors: JACKSON J. A. , PATENAUDE N. J. , CARROLL E. L. , BAKER C. SCOTT 
Published: September 2007

AbstractReconstructing the history of exploited populations of whales requires fitting a trajectory through at least three points in time: (i) prior to exploitation, when abundance is assumed to be at the maximum allowed by environmental carrying capacity; (ii) the point of minimum abundance or ‘bottleneck’, usually near the time of protection or the abandonment of the hunt; and (iii) near the present, when protected populations are assumed to have undergone some recovery. As historical abundance is usually unknown, this trajectory must be extrapolated according to a population dynamic model using catch records, an assumed rate of increase and an estimate of current abundance, all of which have received considerable attention by the International Whaling Commission (IWC). Relatively little attention has been given to estimating minimum abundance (Nmin), although it is clear that genetic and demographic forces at this point are critical to the potential for recovery or extinction of a local population. We present a general analytical framework to improve estimates ofNminusing the number of mtDNA haplotypes (maternal lineages) surviving in a contemporary population of whales or other exploited species. We demonstrate the informative potential of this parameter as anaposterioriconstraint on Bayesian logistic population dynamic models based on the IWC Comprehensive Assessment of the intensively exploited southern right whales (Eubalaena australis) and published surveys of mtDNA diversity for this species. Estimated historical trajectories from all demographic scenarios suggested a substantial loss of mtDNA haplotype richness as a result of 19th century commercial whaling and 20th century illegal whaling by the Soviet Union. However, the relatively high rates of population increase used by the IWC assessment predicted a bottleneck that was implausibly narrow (median, 67 mature females), given our corrected estimates ofNmin. Further, high levels of remnant sequence diversity (theta) suggested that pre‐exploitation abundance was larger than predicted by the logistic model given the catch record, which is known to be incomplete. Our results point to a need to better integrate evolutionary processes into population dynamic models to account for uncertainty in catch records, the influence of maternal fidelity on metapopulation dynamics, and the potential for inverse density dependence (an ‘Allee effect’) in severely depleted populations.
The origin of Phoxinus eos‐neogaeus unisexual hybrids
Authors: ANGERS BERNARD , SCHLOSSER ISAAC J. 
Published: September 2007

AbstractPhoxinus eos‐neogaeus unisexual hybrids (Cyprinidae, Pisces) are among the few vertebrate taxa known to reproduce clonally by gynogenesis. These taxa have a broad distribution in North America, mostly located in regions previously covered by the last Pleistocene ice sheet. To assess whether asexual hybrids dispersed from glacial refuges at the end of the Pleistocene or they originated from current hybridization events, genetic diversity of mitochondrial DNA (mtDNA) sequences and microsatellite loci was determined in populations from 16 different sites in the Mississippi–Missouri River (Nebraska and Montana), Rainy River–Hudson Bay (Minnesota), and St Lawrence River (Quebec) drainages. The maternal species (P. neogaeus) occurred in Minnesota and Nebraska but was absent from Montana sites and was restricted to only two of 11 lakes sampled in Quebec, although hybrids were present at all sites. The genetic survey revealed a total of 49 clones, originating from 14 hybridization events. Several of the lineages were characterized by mtDNA haplotypes not detected in the maternal ancestor. Lineages as well as clones frequently displayed a large geographical distribution at a regional scale. Dating of hybridization events suggested a relatively recent origin (< 50 000 years ago) from the Mississippi glacial refuge, even in regions not covered by the last Pleistocene glacier. Altogether, these results indicate P. eos‐neogaeus hybrids are not the result of current hybridization events, but display a pattern predicted by postglacial dispersal. Our findings have considerable implications for the nature of selection processes affecting the diversity of these asexual taxa and their coexistence with sexual ancestors.
A role for oxidative stress in the Citrus limon/Phoma tracheiphila interaction
Authors: Reverberi M. , Betti C. , Fabbri A. A. , Zjalic S. , Spadoni S. , Mattei B. , Fanelli C. 
Published: September 2007

Phoma tracheiphila, the agent of citrus ‘mal secco’, releases a toxic complex called malseccin into the plant. Oxidative stress was studied, both regarding the reaction of lemon (Citrus limon) leaves to the infiltration of fungal extracellular proteins, and the analysis of the pathogen's ability to cause symptoms in leaves of lemon cultivars with different degrees of susceptibility. Studies were perfomed in planta on three lemon cultivars: cv. Interdonato, partially tolerant to ‘mal secco’; cv. Monachello, tolerant; and cv. Femminello, susceptible. When inoculated with P. tracheiphila extracellular proteins, cv. Interdonato leaves showed chlorosis and necrosis symptoms and an increase in lipoxygenase and glutathione peroxidase of up to 100 and 76·5 fold, respectively. Furthermore, extracellular proteins of P. tracheiphila infiltrated into leaves induced lipoperoxide formation 10 fold in cvs Interdonato and Femminello and 3 fold in cv. Monachello compared to the control, with Monachello reacting earlier. In vitro analyses indicate that the presence of lyophilized twigs and leaves (LTV) of cv. Monachello in the fungal growth medium, stimulated concentrations of superoxide dismutases (~20–60 fold), glutathione peroxidase (~115 fold) and catalase (~15 fold) in fungal mycelia. When LTV of cv. Femminello was added, the pathogen produced a higher quantity of hydrolytic enzymes in vitro, polygalacturonase (~40 fold) and laccase (~110 fold). The MALDI‐TOF and TOF/TOF MS analyses performed on 60–70 KDa extracellular proteins of P. tracheiphila after inoculation in malseccin conducive media showed the presence of a monoamine oxidase enzyme able to release and H2O2 in the cell. Overall the results suggest oxidative stress occurs in this interaction.
Genetic variation in populations of the cacao wilt pathogen, Ceratocystis cacaofunesta
Authors: Engelbrecht C. J. B. , Harrington T. C. , Alfenas A. C. , Suarez C. 
Published: September 2007

Ceratocystis cacaofunesta (= Ceratocystis fimbriata) causes a lethal wilt disease of cacao (Theobroma cacao) in Latin America. Polymorphic microsatellite markers, (CAT)5 nuclear DNA fingerprints and Hae III mitochondrial DNA fingerprints were used to compare genetic diversity among isolates of C. cacaofunesta collected from populations in western Ecuador, Costa Rica, Colombia, and Rondônia and Bahia in Brazil. Microsatellite markers and nuclear DNA fingerprints separated Ecuadorian isolates from isolates of the other four populations, and these two major groups correspond to genetic lineages already identified from ITS‐rDNA sequences and intersterility groupings. Mitochondrial DNA fingerprints also demonstrated substantial diversity and split the Ecuadorian isolates into two groups. All marker types showed limited variation in the Colombian, Costa Rican and Bahian populations, as might be expected for introduced populations that have gone through recent genetic bottlenecks. In contrast, the Rondonian and western Ecuadorian populations showed gene diversity values similar to natural populations of other Ceratocystis species. The Rondonian population was the only sampled population in the native range of T. cacao (the Upper Amazon), and the putatively introduced populations were more closely related to the Rondonian population than to the western Ecuadorian population. The Ecuadorian population is in an area with other native Theobroma species, which may serve as natural hosts.
Late Quaternary contourites and glaciomarine sedimentation in the Fram Strait
Authors: HOWE JOHN A. , SHIMMIELD TRACY M. , HARLAND REX , Eyles Nick 
Published: September 2007

AbstractTwo sites in the eastern Fram Strait, the Vestnesa Ridge and the Yermak Plateau, have been surveyed and sampled providing a depositional record over the last glacial‐interglacial cycle. The Fram Strait is the only deep‐water connection from the Arctic Ocean to the North Atlantic and contains a marine sediment record of both high latitude thermohaline flow and ice sheet interaction. On the Vestnesa Ridge, the western Svalbard margin, a sediment drift was identified in 1226 m of water. Gravity and multicores from the crest of the drift recovered turbidites and contourites. 14C dating indicates an age range of 8287 to 26 900 years BP (Early Holocene to Late Weichselian). The Yermak Plateau is characterized by slope sediments in 961 m of water. Gravity and multicores recovered contourites and hemipelagites. 14C ages were between 8615 and 46 437 years BP (Early Holocene to mid‐Weichselian). Downcore dinoflagellate cyst analyses from both sites provide a record of changing surface water conditions since the mid‐Weichselian, suggesting variable sea ice extent, productivity and polynyas present even during the Last Glacial Maximum. Four layers of ice‐rafted debris were also identified and correlated within the cores. These events occurred ca at 9, 24 to 25, 26 to 27 and 43 ka, asynchronous with Heinrich layers in the wider north‐east Atlantic and here interpreted as reflecting instability in the Svalbard/Barents Ice sheet and the northward advection of warm Atlantic water during the Late Weichselian. The activity of the ancestral West Spitsbergen Current is interpreted using mean sortable silt records from the cores. On the Vestnesa Ridge drift the modern mass accumulation rate, calculated using excess 210Pb, is 0·076 g cm−2 year−1. On the Yermak Plateau slope the modern mass accumulation rate is 0·053 g cm−2 year−1.
Petrography and textural development of inorganic and biogenic lithotypes in a relict barite tufa deposit at Flybye Springs, NT, Canada
Authors: BONNY SANDY M. , JONES BRIAN , Rankey Gene 
Published: September 2007

AbstractA relict mound of Holocene barite (BaSO4) tufa underlies the Flybye Springs, a small, barium‐rich, cold sulphur spring system in the Northwest Territories of Canada. The tufa is composed of relatively pure barite with ≤0·34 wt% Ca2+ and ≤0·77 wt% Sr2+. The mound is made up of coated bubble, raft, undulatory sheet, stromatolitic, coated grain and detrital conglomerate barite tufa. Although previously unreported in barite, these lithotypes are akin to facies found in many carbonate spring deposits. Raft and ooid‐coated grain tufa was formed via ‘inorganic’ barite precipitation in spring water ponds and tributaries where rapid oxidation of sulphide to sulphate established barite supersaturation. Undulatory sheet tufa may have formed by the reaction of dissolved barium with sulphate derived from the oxidation of extracellular polysaccharide‐rich colloidal sulphur films floating in oxygenated, barite‐saturated spring water ponds. Coated bubble, oncoid‐coated grain and stromatolitic tufa with filamentous microfossils was formed in close association with sulphur‐tolerant microbes inhabiting dysoxic and oxygenated spring water tributaries and ponds. Adsorption of dissolved barium to microbial extracellular polysaccharide probably facilitated the development of these ‘biogenic’ lithotypes. Detrital conglomerate tufa was formed by barite cementation of microdetrital tufa, allochthonous lithoclasts and organic detritus, including caribou hair. Biogenic textures, organic artefacts and microfossils in the Flybye barite tufa have survived diagenetic aggradational recrystallization and precipitation of secondary cements, indicating the potential for palaeoecological information to be preserved in barite in the geological record. Similarities between the Flybye barite tufa and carbonate spring deposits demonstrate that analogous textures can develop in chemical sedimentary systems with distinct mineralogy, biology and physiochemistry.
Function of plastidial pyruvate kinases in seeds of Arabidopsis thaliana†
Authors: Baud Sébastien , Wuillème Sylvie , Dubreucq Bertrand , De Almeida Aurélie , Vuagnat Cindy , Lepiniec Loïc , Miquel Martine , Rochat Christine 
Published: September 2007

SummaryPyruvate kinase (PK) catalyses the irreversible synthesis of pyruvate and ATP, which are both used in multiple biochemical pathways. These compounds are essential for sustained fatty acid production in the plastids of maturing Arabidopsis embryos. Using a real‐time quantitative reverse transcriptase (RT)‐PCR approach, the three genes encoding putative plastidial PKs (PKps) in Arabidopsis, namely PKp1 (At3g22960), PKp2 (At5g52920) and PKp3 (At1g32440), were shown to be ubiquitously expressed. However, only PKp1 and PKp2 exhibited significant expression in maturing seeds. The activity of PKp1 and PKp2 promoters was consistent with this pattern, and the study of the PKp1:GFP and PKp2:GFP fusion proteins confirmed the plastidial localization of these enzymes. To further investigate the function of these two PKp isoforms in seeds comprehensive functional analyses were carried out, including the cytological, biochemical and molecular characterization of two pkp1 and two pkp2 alleles, together with a pkp1pkp2 double mutant. The results obtained outlined the importance of these PKps for fatty acid synthesis and embryo development. Mutant seeds were depleted of oil, their fatty acid content was drastically modified, embryo elongation was retarded and, finally, seed germination was also affected. Together, these results provide interesting insights concerning the carbon fluxes leading to oil synthesis in maturing Arabidopsis seeds. The regulation of this metabolic network by the WRINKLED1 transcription factor is discussed, and emphasizes the role of plastidial metabolism and the importance of its tight regulation.
Redox‐sensitive GFP in Arabidopsis thaliana is a quantitative biosensor for the redox potential of the cellular glutathione redox buffer
Authors: Meyer Andreas J. , Brach Thorsten , Marty Laurent , Kreye Susanne , Rouhier Nicolas , Jacquot Jean‐Pierre , Hell Rüdiger 
Published: September 2007

SummaryThe cellular glutathione redox buffer is assumed to be part of signal transduction pathways transmitting environmental signals during biotic and abiotic stress, and thus is essential for regulation of metabolism and development. Ratiometric redox‐sensitive GFP (roGFP) expressed in Arabidopsis thaliana reversibly responds to redox changes induced by incubation with H2O2 or DTT. Kinetic analysis of these redox changes, combined with detailed characterization of roGFP2 in vitro, shows that roGFP2 expressed in the cytosol senses the redox potential of the cellular glutathione buffer via glutaredoxin (GRX) as a mediator of reversible electron flow between glutathione and roGFP2. The sensitivity of roGFP2 toward the glutathione redox potential was tested in vivo through manipulating the glutathione (GSH) content of wild‐type plants, through expression of roGFP2 in the cytosol of low‐GSH mutants and the endoplasmic reticulum (ER) of wild‐type plants, as well as through wounding as an example for stress‐induced redox changes. Provided the GSH concentration is known, roGFP2 facilitates the determination of the degree of oxidation of the GSH solution. Assuming sufficient glutathione reductase activity and non‐limiting NADPH supply, the observed almost full reduction of roGFP2 in vivo suggests that a 2.5 mm cytosolic glutathione buffer would contain only 25 nm oxidized glutathione disulfide (GSSG). The high sensitivity of roGFP2 toward GSSG via GRX enables the use of roGFP2 for monitoring stress‐induced redox changes in vivo in real time. The results with roGFP2 as an artificial GRX target further suggest that redox‐triggered changes of biologic processes might be linked directly to the glutathione redox potential via GRX as the mediator.
Disruption of ATCSLD5 results in reduced growth, reduced xylan and homogalacturonan synthase activity and altered xylan occurrence in Arabidopsis
Authors: Bernal Adriana Jimena , Jensen Jakob Krüger , Harholt Jesper , Sørensen Susanne , Moller Isabel , Blaukopf Claudia , Johansen Bo , De Lotto Robert , Pauly Markus , Scheller Henrik Vibe , Willats William G.T. 
Published: September 2007

SummaryMembers of a large family of cellulose synthase‐like genes (CSLs) are predicted to encode glycosyl transferases (GTs) involved in the biosynthesis of plant cell walls. The CSLA and CSLF families are known to contain mannan and glucan synthases, respectively, but the products of other CSLs are unknown. Here we report the effects of disrupting ATCSLD5 expression in Arabidopsis. Both stem and root growth were significantly reduced in ATCSLD5 knock‐out plants, and these plants also had increased susceptibility to the cellulose synthase inhibitor isoxaben. Antibody and carbohydrate‐binding module labelling indicated a reduction in the level of xylan in stems, and in vitro GT assays using microsomes from stems revealed that ATCSLD5 knock‐out plants also had reduced xylan and homogalacturonan synthase activity. Expression in Nicotiana benthamiana of ATCSLD5 and ATCSLD3, fluorescently tagged at either the C‐ or the N‐terminal, indicated that these GTs are likely to be localized in the Golgi apparatus. However, the position of the fluorescent tag affected the subcellular localization of both proteins. The work presented provides a comprehensive analysis of the effects of disrupting ATCSLD5 in planta, and the possible role(s) of this gene and other ATCSLDs in cell wall biosynthesis are discussed.