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101.
Anders Nielsen Ingolf Steffan-Dewenter Catrin Westphal Olivia Messinger Simon G. Potts Stuart P. M. Roberts Josef Settele Hajnalka Szentgy?rgyi Bernard E. Vaissi��re Michalis Vaitis Michal Woyciechowski Ioannis Bazos Jacobus C. Biesmeijer Riccardo Bommarco William E. Kunin Thomas Tscheulin Ellen Lamborn Theodora Petanidou 《Ecological Research》2011,26(5):969-983
The decline of bees has raised concerns regarding their conservation and the maintenance of ecosystem services they provide to bee-pollinated wild flowers and crops. Although the Mediterranean region is a hotspot for bee species richness, their status remains poorly studied. There is an urgent need for cost-effective, reliable, and unbiased sampling methods that give good bee species richness estimates. This study aims: (a) to assess bee species richness in two common Mediterranean habitat types: semi-natural scrub (phrygana) and managed olive groves; (b) to compare species richness in those systems to that of other biogeographic regions, and (c) to assess whether six different sampling methods (pan traps, variable and standardized transect walks, observation plots and trap nests), previously tested in other European biogeographic regions, are suitable in Mediterranean communities. Eight study sites, four per habitat type, were selected on the island of Lesvos, Greece. The species richness observed was high compared to other habitat types worldwide for which comparable data exist. Pan traps collected the highest proportion of the total bee species richness across all methods at the scale of a study site. Variable and standardized transect walks detected the highest total richness over all eight study sites. Trap nests and observation plots detected only a limited fraction of the bee species richness. To assess the total bee species richness in bee diversity hotspots, such as the studied habitats, we suggest a combination of transect walks conducted by trained bee collectors and pan trap sampling. 相似文献
102.
Yogan Monnier Bruno Vila Nicolas Mont��s Anne Bousquet-M��lou Bernard Pr��vosto Catherine Fernandez 《Trees - Structure and Function》2011,25(3):497-507
Pinus halepensis Mill., is a Mediterranean pioneer forest species with shade-intolerant features. The purpose of this study is to better understand
how stand fertility and allelopathic properties of adult trees influence shade acclimation of saplings. Crown growth and morphological
plasticity were studied under different light, fertilization, and allelopathic conditions in a nursery experiment. We tested
whether shade-acclimation capacity increases with fertilization, and is affected by autotoxicity due to pine leachates. We
examined stem diameter, and crown characteristics (length, width, shape, and density) in a factorial experiment with two levels
for each tested factor: light (full and 20% reduced light), fertilization (low and high rate of NPK fertilizer) and allelopathy
(control and allelopathic leachates uptake). In our study, shading induced a significantly higher crown length, width, and
surface. Fertilization strongly increased crown length and vertical expended crown shape (the ratio crown length/crown width).
Leachates uptake reduced crown length and density, highlighting an autotoxicity phenomenon. We concluded that P. halepensis saplings presented a shade-avoiding syndrome and that the crown shade-acclimation response increased with fertilization but
was severely compromised by autotoxicity. We finally discuss the role of fertilization and allelopathy in early P. halepensis acclimation ability. 相似文献
103.
104.
Claudia C. Soliz-Gamboa Dana? M. A. Rozendaal Greg��rio Ceccantini Veronica Angyalossy Klaas van der Borg Pieter A. Zuidema 《Trees - Structure and Function》2011,25(1):17-27
Knowledge on juvenile tree growth is crucial to understand how trees reach the canopy in tropical forests. However, long-term
data on juvenile tree growth are usually unavailable. Annual tree rings provide growth information for the entire life of
trees and their analysis has become more popular in tropical forest regions over the past decades. Nonetheless, tree ring
studies mainly deal with adult rings as the annual character of juvenile rings has been questioned. We evaluated whether juvenile
tree rings can be used for three Bolivian rainforest species. First, we characterized the rings of juvenile and adult trees
anatomically. We then evaluated the annual nature of tree rings by a combination of three indirect methods: evaluation of
synchronous growth patterns in the tree- ring series, 14C bomb peak dating and correlations with rainfall. Our results indicate that rings of juvenile and adult trees are defined
by similar ring-boundary elements. We built juvenile tree-ring chronologies and verified the ring age of several samples using
14C bomb peak dating. We found that ring width was correlated with rainfall in all species, but in different ways. In all, the
chronology, rainfall correlations and 14C dating suggest that rings in our study species are formed annually. 相似文献
105.
Jos�� Climent Roberto San-Mart��n Maria Regina Chambel Sven Mutke 《Trees - Structure and Function》2011,25(2):175-186
Heteroblastic development in pine seedlings includes extreme morphological changes with still unclear adaptive and evolutionary
significance. In particular, Mediterranean and Eurasian pines (section Pinus) living in the Mediterranean basin seem to follow quite distinct developmental trajectories at the seedling stage. Aiming
to confirm this ontogenetic differentiation we performed a nursery experiment with seedlings of five Mediterranean pines (Pinus pinaster, P. brutia, P. halepensis, P. pinea and P. canariensis) and three Eurasian pines (P. sylvestris, P. uncinata, and P. nigra subsp. salzmannii), also including P. radiata as an outgroup. After destructive analyses at two harvest times (9 and 32 weeks), we found sharp differentiation between
Mediterranean and Eurasian pines in a combination of traits linked to shoot heteroblasty. In particular, Mediterranean pines
showed a marked delay in the proportion of adult needles to total needles in the shoot compared to Eurasian species, especially
at the second harvest. However, two Mediterranean pines, P. pinaster and P. brutia showed a slightly higher proportion of secondary needles, and a higher rate of budset at a more advanced stage (68 weeks)
compared to the other three Mediterranean species. Meaningfully, the outgroup P. radiata was the only species combining a high proportion of adult foliage since the first harvest with a delayed formation of the
first terminal bud. We discussed the adaptive significance of these findings at the light of species’ climatic niches and
life histories. 相似文献
106.
Daily sap flow rate as an indicator of drought avoidance mechanisms in five Mediterranean perennial species in semi-arid southeastern Spain 总被引:1,自引:0,他引:1
Daily sap flow rate was determined in five Mediterranean species (Pinus halepensis, Quercus coccifera,
Pistacia lentiscus, Erica multiflora, and Stipa tenacissima) under two slope aspects (north- and south-facing) in a semi-arid area (Alicante, SE Spain). Sap flow velocity was measured
in January, May, August and October of two consecutive years (1998 and 1999) using the stem heat balance (SHB) method. Our
results have demonstrated the effects of global radiation (R
g), vapour pressure deficit (VPD) on the sap flow velocity per unit of leaf area. Mean daily sap flow rates (Q
md) showed values between 0.001 and 0.202 g H2O cm−2 leaf area day−1. Q
md values were higher on the south-facing slope than on the north-facing slope. In most species, the Q
md was higher in 1998 than in 1999 due to the higher soil water content, temperature and VPD in 1998. In all five species, a
decrease in predawn leaf water potential was accompanied by a decrease in mean daily sap flow rates; nevertheless, the responses
of the five species to water deficit conditions were different. In this context, we have linked the drought avoidance mechanisms
of the different species through the combined use of daily sap flow rate and predawn leaf water potential under different
water deficit conditions. We conclude that Pinus halepensis, Pistacia lentiscus and Erica multiflora show water-savers mechanisms to cope with drought, while Quercus coccifera and Stipa tenacissima show water-spenders mechanisms. 相似文献
107.
Chotechuang N Azzout-Marniche D Bos C Chaumontet C Gaudichon C Tomé D 《Amino acids》2011,41(2):457-468
The purpose of this work was to examine whether changes in dietary protein levels could elicit differential responses of tissue proteolysis and the pathway involved in this response. In rats fed with a high protein diet (55%) for 14?days, the liver was the main organ where adaptations occurred, characterized by an increased protein pool and a strong, meal-induced inhibition of the protein breakdown rate when compared to the normal protein diet (14%). This was associated with a decrease in the key-proteins involved in expression of the ubiquitin-proteasome and autophagy pathway gene and a reduction in the level of hepatic ubiquitinated protein. In hepatocytes, we demonstrated that the increase in amino acid (AA) levels was sufficient to down-regulate the ubiquitin proteasome pathway, but this inhibition was more potent in the presence of insulin. Interestingly, AICAR, an adenosine monophosphate-activated protein kinase (AMPK) activator, reversed the inhibition of protein ubiquination induced by insulin at high AA concentrations. Rapamycin, an mammalian target of rapamycin (mTOR) inhibitor, reversed the inhibition of protein ubiquination induced by a rise in insulin levels with both high and low AA concentrations. Moreover, in both low and high AA concentrations in the presence of insulin, AICAR decreased the mTOR phosphorylation, and in the presence of both AICAR and rapamycin, AICAR reversed the effects of rapamycin. These results demonstrate that the inhibition of AMPK and the activation of mTOR transduction pathways, are required for the down-regulation of protein ubiquitination in response to high amino acid and insulin concentrations. 相似文献
108.
Adrenocortical dysplasia (acd) is a spontaneous autosomal recessive mouse mutation exhibiting caudal truncation, vertebral segmentation defects, hydronephrosis, limb hypoplasia, and perinatal lethality. Acd encodes TPP1, a component of the shelterin complex that maintains telomere integrity, and consequently acd mutant mice have telomere dysfunction and genomic instability. We previously showed that apoptosis is the primary mechanism causing the acd skeletal phenotype, and that p53 deficiency rescues the skeletal defects of the acd phenotype but has no effect on the perinatal lethality. The Trp63 gene encodes multiple isoforms, which play a role in proliferation, apoptosis, and stem/progenitor cell maintenance. Different p63 isoforms exhibit both proapoptotic (TAp63) and antiapoptotic (ΔNp63) functions. We hypothesized that deficiency of proapoptotic TAp63 isoforms might rescue the acd skeletal phenotype, similar to our previous observations with deficiency of p53. Mice heterozygous for a null allele of TAp63 were crossed to heterozygous acd mice to determine the effect of TAp63 deficiency on the acd mutant phenotype. In contrast to our results with the acd?×?p53 cross, skeletal anomalies were not rescued by deficiency of TAp63. In fact, the limb and vertebral anomalies observed in double-mutant embryos were more severe than those of embryos with the acd mutation alone, demonstrating a dose-dependent effect. These studies suggest that TAp63 isoforms do not facilitate p53-like apoptosis during development in response to acd-mediated telomere dysfunction and are consistent with the proposed roles of TAp63 in maintaining genomic stability. 相似文献
109.
Fatimazohra Lenda Nadine Crouzin M��lanie Cavalier Janique Guiramand Fabien Lant�� G��rard Barbanel Catherine Cohen-Solal Jean Martinez Farhate Guenoun Fr��d��ric Lamaty Michel Vignes 《Amino acids》2011,40(3):913-922
Five derivatives of 2-amino-adipic acid bearing a tetrazole-substituted in C5 position were synthesized. These compounds displayed selective antagonism towards N-methyl-d-aspartate (NMDA) receptors compared with AMPA receptors, and they were devoid of any neurotoxicity. Among these five analogues, one exhibited a higher affinity for synaptic NMDA responses than the other four. Therefore, C5 tetrazole-substituted of 2-amino-adipic acid represent an interesting series of new NMDA receptor antagonists. This approach may be considered as a new strategy to develop ligands specifically targeted to synaptic or extra-synaptic NMDA receptors. 相似文献
110.