bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ecomorphological correlates of habitat partitioning in Corsican lacertid lizards
Authors: Vanhooydonck B. , Van Damme R. , Aerts P. 
Published: March 2003

Abstract1. Morphological features (i.e. snout–vent length, SVL, mass and limb parameters), locomotor performance (sprint speed, climbing speed, manoeuvrability and endurance) and microhabitat use were measured in three lacertid lizard species. Additionally, microhabitat preference was tested in the laboratory with species kept apart and in combination with each other to assess mutual interference.2. It was predicted that each species possesses morphological adaptations that allow it to excel in those performance measures relevant in its particular microhabitat.3. The three species differed in microhabitat use. Lacerta bedriagae was mostly seen on boulders, while Podarcis sicula occurred among vegetation. Podarcis tiliguerta seemed more general in its microhabitat use. The results from the microhabitat preference in the laboratory corresponded well to these field observations.4. Besides differing in SVL, the three species differed in limb length and diameter, and body mass (all relative to SVL). L. bedriagae has long forelimbs, short hindlimbs and a high body mass, while P. sicula has short forelimbs, long hindlimbs and a low body mass. P. tiliguerta is morphologically intermediate.5. The differences found in morphology translated partially into performance differences. Only climbing speed and endurance differed among species. L. bedriagae excelled in both cases. Considering its microhabitat use, this seemed adaptive.6. Unexpectedly, the interference experiments suggested that L. bedriagae is the least competitive of the three species.
Elongated chambers for field studies across atmospheric CO2 gradients
Authors: Johnson H. B. , Polley H. W. , Whitis R. P. 
Published: March 2003

Abstract1. We describe a field facility that controls CO2 along continuous gradients from superambient to subambient concentrations. The facility consists of two transparent, tunnel‐shaped chambers, each 1‐m wide and tall and 60‐m long. Pure CO2 is injected into one chamber during daylight to initiate a superambient CO2 gradient (550–350 µmol mol−1). Ambient air is introduced to the second chamber to initiate a subambient CO2 gradient (350–200 µmol mol−1). CO2 concentrations at night are regulated at 150 µmol mol−1 above daytime values along each gradient. The CO2 gradients are maintained by varying the rate and direction (day/night) of air flow.2. Air temperature and vapour pressure deficit are regulated near ambient values by cooling and dehumidifying air at 5‐m intervals along chambers.3. Desired CO2 gradients were regulated on grassland for virtually the entire 9‐month growing season in 1998, including a 6‐month drought. Consistent CO2 concentrations were maintained along gradients despite seasonal variation in species composition, leaf area, and temperature.4. Daytime temperatures in chambers tracked the seasonal pattern in 1998. The polyethylene covering on chambers transmitted 90% of incident light, but usually increased the ratio of diffuse to direct light.5. By enabling the study of trends in plant and ecosystem responses to CO2 over both subambient and superambient concentrations, elongated chambers fill a void in CO2 research facilities.
Photosynthetic refixation in branches of Western White Pine
Authors: L. A. Cernusak , J. D. Marshall 
Published: March 2003

Abstract1. We investigated the functional controls on light‐dependent refixation of respired CO2 in photosynthetic bark of Western White Pine (Pinus monticola Dougl. ex D. Don) branches.2. Gross photosynthesis increased with increasing intensity of photosynthetically active radiation (PAR) to > 2000 µmol m−2 s−1 and with increasing bark surface temperature from 15 to > 45 °C. Maximum observed refixation rates were 76 ± 3% (mean ± SE) of dark respiration.3. At a given temperature and irradiance, dark respiration rate was the physiological parameter that correlated most strongly with gross photosynthesis (R = 0·89, P < 0·0001, n = 43). Dark respiration rates varied 20‐fold among branches. Over this range, refixation averaged 55 ± 2% of dark respiration at 25 °C and 1000 µmol PAR m−2 s−1. However, refixation was not correlated with internal CO2 concentrations in illuminated branches; these concentrations remained fairly constant.4. Specific bark area, bark conductance to water vapour, bark chlorophyll a/b ratio, and bark nitrogen concentration varied markedly with canopy depth in mature trees.5. Results are summarized in a simple model of refixation driven by light, temperature and dark respiration rate. The model may prove useful in assessing the quantitative significance of refixation in the carbon balance of forest trees.
Physical apertures as constraints on egg size and shape in the Common Musk Turtle, Sternotherus odoratus
Authors: Clark P. J. , Ewert M. A. , Nelson C. E. 
Published: March 2003

Summary

Egg size in turtles often increases with female size, contrary to expectations of optimality. Functional constraints on egg width imposed by the pelvic aperture or the gap between the carapace and plastron (the caudal gap) have been inferred for a few populations but appear inapplicable in others.
For Sternotherus odoratus (the Common Musk Turtle), the pelvic aperture was always wider than the width of the female’s largest egg by at least 3·7 mm. The caudal gap was narrower than the widest egg for 25·7% of the females.
Egg width increased, and elongation (length/width) decreased, as female size and clutch size increased.
Females at three ecologically contrasting sites differed appreciably in size but produced eggs of the same mean shape and size, despite the strong within‐site changes in both egg size and shape with female size. As the younger females at all sites were of similar age and produced eggs of similar size and shape (again, despite differences in body size), egg size and shape may be age‐specific.
No optimal egg size prevailed but the scaled residuals of egg size with female mass were less variable than were those for clutch size.
Allometric and ecological relationships of ventricle and liver mass in anuran amphibians
Authors: Withers P. C. , Hillman S. S. 
Published: March 2003

Summary There is an isometric relationship for allometry of ventricle mass (slope = 0·952) and liver mass (slope = 1·027) and phylogenetic correlations of ventricle and liver mass for museum specimens of 42 species of Australian frogs. There was a strong relationship for ventricle mass with body mass, phylogeny and dehydration tolerance, but not habit, body shape or environmental variables. The relatively large ventricle of more dehydration‐tolerant species may also be associated with a higher metabolic scope for activity. There was a strong relationship for liver mass with body mass, phylogeny, habit (burrowing, terrestrial, arboreal), body shape and some environmental variables, but not dehydration tolerance. For burrowing frogs, a relatively large liver is presumably important because it is an energy store during long periods of dormancy and is a source of amino acids for cocoon formation or urea synthesis. For arboreal frogs, a small liver might reduce the cost of transport by limiting body mass, and allow a more elongate shape. Relative ventricle mass of museum specimens is representative of values for field‐collected frogs. Relative liver mass is higher for museum specimens; this might be an artefact of museum preservation and/or reflect seasonal or geographic variation.
Soil and atmospheric water deficits and the distribution of New Zealand’s indigenous tree species
Authors: J. R. Leathwick , Whitehead D. 
Published: March 2003

Summary1. An extensive data set describing the composition of New Zealand’s remaining indigenous forests was used to estimate the degree of correlation between measures of both soil and atmospheric water deficit and the distribution of common tree species.2. For most species, regression models incorporating measures of air saturation deficit in early autumn, as well as an annual integral of root zone water deficit, provided the best explanation of spatial distribution. This accords strongly with the mechanistic effects of air saturation deficits on transpiration from trees, and the hydraulic risks experienced by trees under high evaporative demand.3. Adjustment of root zone water deficits to account for reductions in rainfall in dry years substantially improved model predictions. This suggests that extreme climatic events, such as the El Niño phase of the Southern Oscillation, are likely to have strongly influenced the historic composition of forests in New Zealand’s drier eastern lowlands.
Relative importance of microhabitat, plant form and photosynthetic physiology to carbon gain in two alpine herbs
Authors: Germino M. J. , Smith W. K. 
Published: March 2003

Abstract1. The effects of microhabitat and plant form on sunlight interception, leaf temperatures, frost occurrence and photosynthesis were evaluated for Caltha leptosepala DC and Erythronium grandiflorum Pursh. Both plants are perennials that commonly emerge from alpine snowbanks where the combination of cool temperatures and strong sunlight is among the most extreme for vascular plants.2.  Caltha leptosepala occurred in microsites where colder air accumulates, and has larger, less inclined and more densely clustered leaves compared to E. grandiflorum (which has two steeply inclined leaves).3. These differences in microsite and plant form led to leaf temperatures below 0 °C on 70% of nights during the summer growth season in C. leptosepala, compared to only 38% in E. grandiflorum. Leaves of C. leptosepala warmed more slowly on mornings following frosts compared to E. grandiflorum, due to less aerodynamic coupling between leaf and air temperature, and also a 45% smaller ratio of sunlit to total leaf area due to mutual shading among leaves.4. As a result, night frost did not affect subsequent CO2 assimilation (A) in E. grandiflorum, while frostless nights and warmer mornings led to 35% greater A in C. leptosepala in the early morning.5. There were no appreciable differences in the temperature and light response of photosynthesis between the two species. The apparent quantum yield of A declined only ≈8% in both species following frost and exposure to strong sunlight, indicating little adjustment of photosynthetic physiology.6. Greater daily carbon gain probably occurs for E. grandiflorum because of its plant form and microclimate, rather than differences in photosynthetic physiology.
Species‐level versus community‐level patterns of mycorrhizal dependence on phosphorus: an example of Simpson’s paradox
Authors: Allison V. J. , Goldberg D. E. 
Published: March 2003

Summary 1. Ecological studies commonly assume that it is possible to extrapolate from a response shown by a fixed set of species to the response when the species composition is allowed to change. However, as described by Simpson’s paradox, this is not necessarily a reasonable expectation. 2. The impact of Simpson’s paradox on an ecological question was tested using a meta‐analysis of data on plant responses to arbuscular mycorrhizas. Although species‐level response commonly declines as phosphorus availability increases, we hypothesized that the community‐level response could either decline or remain constant. 3. As expected, mycorrhizal response of individual species declined significantly as P supply increased. The response averaged across multiple species was negative but not robust, so we cannot distinguish clearly between the hypotheses. 4. It is impossible to assume that community‐level responses to environmental gradients are the same as those found at species level. We recommend that experimental tests of hypotheses should allow species identity to change with the environment.
Survival of terrestrial soil‐dwelling arthropods on and in seawater: implications for trans‐oceanic dispersal
Authors: Coulson S. J. , Hodkinson I. D. , Webb N. R. , Harrison J. A. 
Published: March 2003

Summary1. The ability of six species of high Arctic soil arthropod to survive oceanic transport in or on sea water was tested experimentally.2. Five species of Collembola,Hypogastrura tullbergi(Schäffer),Onychiurus groenlandicus(Tullberg),Onychiurus arcticus(Tullberg),Folsomia quadrioculata(Tullberg) andTetracanthella arcticaSchött were exposed on the surface film of seawater in chambers agitated within a shaking water bath.3. All five species survived for over 14 days, at the end of which survival among species varied between 27 and 100%.4. In a separate experiment the cryptostigmatic miteCamisia anomiaColloff and the ‘wettable’ collembolanT. arcticasurvived submersion in sea water for longer than 2 weeks. Survival ofC. anomiaexceeded 75% but that ofT. arctica, when submerged, fell to 12%.5. Survival times are sufficient to permit ocean current transport from northern Norway to Svalbard in the high Arctic, a distance of around 700 km. The implications of the experiments for long‐distancetrans‐oceanic dispersal of non‐specialized soil arthropods are discussed.
Effects of low calcium concentrations on two common freshwater crustaceans, Gammarus lacustris and Astacus astacus
Authors: Rukke N. A. 
Published: March 2003

Summary 1. Field studies indicate that low Ca concentrations limit the distribution and success of Ca‐demanding freshwater crustaceans in soft‐water localities. A long‐lasting depletion of Ca caused by reversed acidification could thus be detrimental to such species. 2. Experimental studies of Gammarus lacustris and Astacus astacus revealed decreased survival and retarded growth at ambient Ca concentrations <5 mg l−1, compared with animals reared at 10 mg l−1. 3. A significant proportion of the total body Ca content was lost during the moult, but moulting frequencies were not affected by ambient Ca concentration. Complete postmoult calcification of the carapace could not be achieved at ambient Ca concentrations <5 mg l−1, and individuals reared at such conditions had a lower specific Ca content than individuals reared at sufficient Ca levels. 4. A juvenile bottleneck regarding the susceptibility to Ca deficiency was shown in G. lacustris, as neonates had a relatively higher mass‐specific Ca content and a higher Ca threshold for survival than adults. 5. Because of a short postmoult calcification period of less than 2 days, G. lacustris had limited ability to compensate for low water Ca levels by obtaining Ca from food. However, food might be an important source of Ca for A. astacus living at low ambient Ca, because eating could be resumed during the relatively long calcification period (>15 days).
Soil organic matter distribution and below‐ground competition between Calluna vulgaris and Nardus stricta
Authors: Genney D. R. , Alexander I. J. , Hartley S. E. 
Published: March 2003

Summary

We conducted an experiment to investigate the effect of organic matter distribution on below‐ground competition between the dwarf shrub Calluna vulgaris (L.) Hull and the coarse upland grass Nardus stricta (L.).
The two species were grown alone, or in competition in pots where the substrate was either a sand layer overlain by a peat layer (layered), or the same volume of peat evenly mixed with sand throughout the pot (mixed).
Root length and allocation in the top, middle and bottom of each pot was measured, along with plant biomass.
Calluna allocated the greatest proportion of root length to the top of the pot, irrespective of the peat distribution. Nardus allocated a large proportion of root length to the bottom of the pot. Root allocation by Nardus to the top and middle of the pot was positively related to the distribution of peat.
Nardus grown alone attained greater shoot mass in the layered than in the mixed substrate, but this was not the case when Calluna was present. Calluna was the superior competitor in both layered and mixed‐substrate pots, but more so in the latter.
This was attributed to (i) the ability of Calluna to exclude Nardus roots from the upper organic material in the layered substrate, and (ii) the greater plasticity of root allocation of Nardus, enabling it to avoid competition with Calluna.
Phosphorus uptake, not carbon transfer, explains arbuscular mycorrhizal enhancement of Centaurea maculosa in the presence of native grassland species
Authors: Zabinski C. A. , Quinn L. , Callaway R. M. 
Published: March 2003

Summary

Previous studies have shown that arbuscular mycorrhizas (AM) enhance the growth of the invasive forb Centaurea maculosa when growing with native grass species. Using 13CO2, we tested the hypothesis that this enhancement is explained by carbon transfer from native species to C. maculosa via mycorrhizal hyphal linkages.
A C. maculosa plant was paired with one of five native species – three grasses (Festuca idahoensis, Koeleria cristata and Pseudoroegneria spicata) and two forbs (Achillea millefolium and Gaillardia aristata) – in pots that separated the plants with either a mesh barrier (28 µm, excludes fine roots but not hyphae) or a membrane barrier (0·45 µm, excludes roots and hyphae).
13CO2 was added to the atmosphere of either Centaurea or the native species after 20 weeks’ growth. A 25 min pulse application was followed by 7 days’ growth and subsequent harvest.
The biomass response of C. maculosa was consistent with previous experiments: C. maculosa was larger when growing in mesh barrier pots, when hyphae were able to access the opposite side of the pot; in mesh barrier pots only, biomass varied with neighbouring species. Native plant biomass did not vary between mesh‐ vs membrane‐barrier pots.
There was no evidence of carbon transfer, either from the native plant to C. maculosa or in the reverse direction.
Centaurea maculosa contained significantly more phosphorus in mesh‐divided pots, but this depended on the neighbouring plant. The P concentration in C. maculosa was significantly higher in mesh‐divided pots when growing with a grass and not a forb. Native species contained more P in mesh‐divided pots than membrane‐divided pots, and P concentration differed between species (higher in forbs than grasses), but did not vary between mesh‐ and membrane‐divided pots.
Our study suggests that C. maculosa is able to exploit its mycorrhizal symbiosis more effectively than the native grassland species. The mechanism for this appears to be luxury consumption of P through efficient utilization of extra‐radical hyphae, but that effect is dependent on neighbouring species, and occurs when growing with a grass neighbour.
Although no single study can disprove the carbon‐transfer hypothesis, our work suggests that AM‐mediated neighbour effects are the result of mycorrhizal networks that increase species’ access to P. Whether the synergistic effects of neighbours are due to complementarity of AM fungal symbionts utilized by different plant species, or have to do with the structure of AM networks that develop more extensively with multiple host plants, remains to be investigated.
Human ubiquitin‐protein ligase Nedd4: expression, subcellular localization and selective interaction with ubiquitin‐conjugating enzymes
Authors: Anan Tadashi , Nagata Yoichi , Koga Hisashi , Honda Yoshiomi , Yabuki Nami , Miyamoto Chikara , Kuwano Akira , Matsuda Ichiro , Endo Fumio , Saya Hideyuki , Nakao Mitsuyoshi 
Published: March 2003

BackgroundNedd4 is a ubiquitin‐protein ligase containing a calcium/lipid‐binding domain, multiple WW domains and a C‐terminal Hect domain, which is required for both the ubiquitin transfer and the association with E2 ubiquitin‐conjugating enzymes. Nedd4 has been reported to be involved in the selective ubiquitination of some regulatory proteins in transcription and membrane transport.ResultsThree mRNA species for human Nedd4 were found to be 6.4‐, 7.8‐ and 9.5‐kb in size, and their expression patterns varied among normal tissues and cancer cell lines, indicating the tissue‐ and cell‐specificities of Nedd4 expression. The Nedd4 protein, ≈120 kDa in weight, was found in the cytoplasm, mainly in the perinuclear region and cytoplasmic periphery, of human cultured cells. Neural differentiation induced not only the down‐regulation of Nedd4 but also the localization of the protein to both the cytoplasm and neurites. To identify the ubiquitination pathway that is linked to Nedd4, we demonstrated that specific E2 enzymes, including human Ubc4, UbcH5B, UbcH5C, UbcH6 and UbcH7, could transfer ubiquitin molecules to Nedd4 at the active cysteine residue, whereas E6AP accepted ubiquitins from Ubc4, UbcH5B, UbcH5C and UbcH7. Furthermore, nuclear localization of N‐terminal deletion mutant Nedd4 enabled us to investigate the interaction between Nedd4 and E2 enzyme (Ubc4 or UbcH7) in the cell. The simultaneous expression of the full‐length Nedd4 and E2 enzyme revealed that both proteins mostly colocalized in the cytoplasmic periphery, while the N‐terminal deleted Nedd4 induced the nuclear and perinuclear colocalization with E2 enzyme.ConclusionOur findings suggested that Nedd4 plays an important role in the cell regulation, including neural differentiation through cooperation with specific E2 ubiquitination pathways.
Incorporation of Drosophila TAF110 into the yeast TFIID complex does not permit the Sp1 glutamine‐rich activation domain to function in vivo
Authors: Keaveney Marie , Struhl Kevin 
Published: March 2003

BackgroundAcidic activation domains function across eukaryotic species, and hence stimulate transcription by a conserved molecular mechanism. In contrast, glutamine‐rich activation domains function in flies, mammals, and fission yeasts but not in the budding yeast Saccharomyces cerevisiae. The glutamine‐rich activation domain of Sp1 interacts with TAF110, and it has been suggested that this interaction is important for transcriptional activation. S. cerevisiae does not contain a homologue of TAF110, suggesting a potential mechanism to account for the failure of glutamine‐rich activation domains to stimulate transcription.ResultsHere, we have artificially recruited Drosophila TAF110 into the yeast TFIID complex by fusing it to yeast TBP. The resulting TFIID complex supports normal cell growth, but it is unable to mediate Sp1‐dependent activation.ConclusionsThus, the interaction of glutamine‐rich activation domains with TAF110 is insufficient for transcriptional activation in vivo, indicating that other targets within the PolII machinery are necessary.
Smad8B, a Smad8 splice variant lacking the SSXS site that inhibits Smad8‐mediated signalling
Authors: Nishita Michiru , Ueno Naoto , Shibuya Hiroshi 
Published: March 2003

BackgroundMembers of the TGF‐β superfamily of ligands bind to and activate surface serine/threonine‐kinase receptors. Transduction of these signals requires the Smad proteins, which transiently interact with the activated receptor complex and are phosphorylated on their C terminus, SSXS site, by the type I receptor. Smad8 is a downstream signalling mediator of ALK2/ActRIA.ResultsWe have cloned a splice variant of Smad8, designated Smad8B. The Smad8 and Smad8B cDNAs are identical in sequence, except that Smad8B lacks a portion encoding 47 amino acids, including the SSXS phosphorylation site, in the C‐terminal MH2 region. Both Smad8 and Smad8B were expressed in many of the same cell types. Smad8B was capable of specific complex formation with either Smad8 or Smad4 in mammalian cells. In cells expressing constitutively activated ALK2, Smad8B was localized to the cytoplasmic region, whereas Smad8 was translocated into the nucleus. In mammalian cells, Smad8B acted as a dominant inhibitor of BMP signalling.ConclusionsSmad8B, a splice variant of Smad8, was isolated and found to specifically associate with both Smad8 and Smad4. Smad8B inhibited BMP signalling. Smad8 and Smad8B thus represent novel signal transduction proteins that may regulate the BMP signalling pathway.