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排序方式: 共有164条查询结果,搜索用时 15 毫秒
71.
Andrea Holzschuh Matteo Dainese Juan P. González‐Varo Sonja Mudri‐Stojnić Verena Riedinger Maj Rundlöf Jeroen Scheper Jennifer B. Wickens Victoria J. Wickens Riccardo Bommarco David Kleijn Simon G. Potts Stuart P. M. Roberts Henrik G. Smith Montserrat Vilà Ante Vujić Ingolf Steffan‐Dewenter 《Ecology letters》2016,19(10):1228-1236
Mass‐flowering crops (MFCs) are increasingly cultivated and might influence pollinator communities in MFC fields and nearby semi‐natural habitats (SNHs). Across six European regions and 2 years, we assessed how landscape‐scale cover of MFCs affected pollinator densities in 408 MFC fields and adjacent SNHs. In MFC fields, densities of bumblebees, solitary bees, managed honeybees and hoverflies were negatively related to the cover of MFCs in the landscape. In SNHs, densities of bumblebees declined with increasing cover of MFCs but densities of honeybees increased. The densities of all pollinators were generally unrelated to the cover of SNHs in the landscape. Although MFC fields apparently attracted pollinators from SNHs, in landscapes with large areas of MFCs they became diluted. The resulting lower densities might negatively affect yields of pollinator‐dependent crops and the reproductive success of wild plants. An expansion of MFCs needs to be accompanied by pollinator‐supporting practices in agricultural landscapes. 相似文献
72.
Marija Miličić Snežana Popov Ante Vujić Bojana Ivošević Pedro Cardoso 《Ecological Entomology》2020,45(2):232-242
1. Dark diversity represents the set of species that can potentially inhabit a given area under particular ecological conditions, but are currently ‘missing’ from a site. This concept allows characterisation of the mechanisms determining why species are sometimes absent from an area that seems ecologically suitable for them. 2. The aim of this study was to determine the dark diversity of hoverflies in south-eastern Europe and to discuss the role of different functional traits that might increase the likelihood of species contributing to dark diversity. Based on expert opinion, the Syrph the Net database and known occurrences of species, the study estimated species pools, and observed and dark diversities within each of 11 defined vegetation types for 564 hoverfly species registered in south-eastern Europe. To detect the most important functional traits contributing to species being in dark diversity across different vegetation types, a random forest algorithm and respective statistics for variable importance were used. 3. The highest dark diversity was found for southwest Balkan sub-Mediterranean mixed oak forest type, whereas the lowest was in Mediterranean mixed forest type. Three larval feeding modes (saproxylic, and phytophagous on bulbs or roots) were found to be most important for determining the probability of a species contributing to hoverfly dark diversity, based on univariate correlations and random forest analysis. 4. This study shows that studying dark diversity might provide important insights into what drives community assembly in south-eastern European hoverflies, especially its missing components, and contributes to more precise conservation prioritisation of both hoverfly species and their habitats. 相似文献
73.
Vesna Milankov Ljubinka Francuski Jasmina Ludoški Gunilla Ståhls Ante Vujić 《Journal of Insect Conservation》2010,14(1):77-88
The genetic structure and phenotypic diversity of a population of Cheilosia naruska Haarto and Kerppola, 2007 (Diptera, Syrphidae) from Lapland, Finland, was examined through allozyme electrophoresis and wing
morphometrics. The morphological identification of the species was verified molecularly using partial sequences of mitochondrial
COI and the nuclear ribosomal ITS2 genes comparing with corresponding sequences of a paratype of the taxon. Based on protein
electrophoresis, out of 12 analyzed allozyme loci, only one locus (Me) was found to be polymorphic. The low genetic variability was further evidenced by the absence of heterozygote genotypes.
Fluctuating asymmetry was used as a measure of developmental stability. For this we used different wing traits that were estimated
using both wing landmark positions and metric traits. Procrustes ANOVA and Canonical variate analysis revealed asymmetry in
wing metric and wing shape and size, and within each sex considered separately. Principal component analysis revealed similar
multivariate patterns of landmark covariation between within-individual variability (fluctuating asymmetry) and variation
among individuals. Finally, the observed association between lack of heterozygosity and high level of asymmetry is discussed
in light of conservation. 相似文献
74.
Vasilj I Bergovec M Kvesić A Strnad M Ostojić L Ostojić Z Martinović V Petrović P Kondza D Vasiljo M 《Collegium antropologicum》2006,30(4):915-919
All patients who suffered from the acute coronary syndrome in western Herzegovina over the fifteen year period (1987-2001) are included in this retrospective epidemiological study. The population that was undertaken by the study is relative stabile and did not emigrate during the war period. The study compared the time before the war (1987-1991), during the war (1992-1996) and after the war (1997-2001). The data were acquired from the archives of the patients of the Mostar hospital and Clinical hospital Split during the war period. A total of 2022 acute coronary syndrome patients were found, 1305 men and 717 women. More patients were treated during the war compared to the time before the war for both male and female patients (p<0.0005). During the after-war period the number of treated patients was greater (p< 0.0005) compared to the war-time for both sexes. The comparison of the after-war period and the pre-war period reveals a statistically significant difference as the number of treated patients (male and female) is larger in the after-war period. The number of patient who are 65 years old and older than that is greater, and that is statistically significant (p= 0.0005.). We can conclude that the stress caused by the war and other factors have influenced a larger number of treated patients of acute coronary syndrome. Therefore, further epidemiological researches of acute coronary syndrome with the accent on prevention and treatment are needed. 相似文献
75.
76.
Multiple aneurysms are clinically common in population aged over sixty and are caused mainly by atherosclerosis. When occurring in young population other etiologies such as trauma, infections, Bechet's disease, Marfan syndrome, neurofibromatosis or inflammatory disease are responsible for the development of arterial aneurysms. A rare case of multiple aneurysms in a 40-year-old man, affecting the infrarenal part of abdominal aorta, both iliac arteries, common femoral arteries, left femoral superficial and popliteal arteries on, both legs, is reported. The underlying pathology was progressive atherosclerosis, favored by familial hyperlipidemia and excessive cigarette smoking. 相似文献
77.
Shaya D Tocilj A Li Y Myette J Venkataraman G Sasisekharan R Cygler M 《The Journal of biological chemistry》2006,281(22):15525-15535
Heparinase II depolymerizes heparin and heparan sulfate glycosaminoglycans, yielding unsaturated oligosaccharide products through an elimination degradation mechanism. This enzyme cleaves the oligosaccharide chain on the nonreducing end of either glucuronic or iduronic acid, sharing this characteristic with a chondroitin ABC lyase. We have determined the first structure of a heparin-degrading lyase, that of heparinase II from Pedobacter heparinus (formerly Flavobacterium heparinum), in a ligand-free state at 2.15 A resolution and in complex with a disaccharide product of heparin degradation at 2.30 A resolution. The protein is composed of three domains: an N-terminal alpha-helical domain, a central two-layered beta-sheet domain, and a C-terminal domain forming a two-layered beta-sheet. Heparinase II shows overall structural similarities to the polysaccharide lyase family 8 (PL8) enzymes chondroitin AC lyase and hyaluronate lyase. In contrast to PL8 enzymes, however, heparinase II forms stable dimers, with the two active sites formed independently within each monomer. The structure of the N-terminal domain of heparinase II is also similar to that of alginate lyases from the PL5 family. A Zn2+ ion is bound within the central domain and plays an essential structural role in the stabilization of a loop forming one wall of the substrate-binding site. The disaccharide binds in a long, deep canyon formed at the top of the N-terminal domain and by loops extending from the central domain. Based on structural comparison with the lyases from the PL5 and PL8 families having bound substrates or products, the disaccharide found in heparinase II occupies the "+1" and "+2" subsites. The structure of the enzyme-product complex, combined with data from previously characterized mutations, allows us to propose a putative chemical mechanism of heparin and heparan-sulfate degradation. 相似文献
78.
Our aim is to investigate starvation as cause of death and social and demographic consequences in the Croatian Quarnero and its hinterland between 1816 and 1825, paying particular attention to the infamous "year of famine" 1817. Our sources were: registers of births, marriages, and deaths from 21 parishes kept at the Croatian State Archives in Rijeka and Zagreb. We collected and processed data for statistical analysis according to the date of baptism (birth), marriage, and death, and according to sex and age. Our focus was on recorded causes of death. Between 1816 and 1825, 15,701 children were baptised (born), and 11,021 people died. Starvation was recorded as cause of death in 255 cases, of which 198 were recorded in the infamous 1817. It was the only year with negative growth in virtually all parishes, with the birth-to-death ratio of 1147:1545. In 1817, the proportion of death by starvation to the total death rate was 12.8% for the entire area, with the highest share recorded in Veprinac (33.3%), Crikvenica (23.3%), and Kastav (15.8%). Death by starvation was more common in men than in women (56.7% vs. 43.3%, respectively). Age distribution was as follows; in the population below 20 years of age the death rate was 42 (16.5% of total deaths), but the most affected age group were infants and children aged 1-4 years (69.0%) whereas in adult population the death rate was 213 (83.5% of total deaths) and the most affected group were the elderly between 60 and 69 years (26.3%). Analysis shows lower birth and marriage rates between 1816 and 1818, followed by a steep rise and a plateau with minimal variation. This study shows that the Croatian Quarnero and its hinterland suffered a great famine in the early 19th century and 1817 in particular, which had left a deep mark on local demography, just like in the neighbouring parts of Croatia and Europe. 相似文献
79.
Janković S Pavicić Ivelja M Kolić K Buca A Dolić K Lovrić Kojundzić S Caljkusić K Bilić I Capkun V 《Collegium antropologicum》2010,34(4):1391-1396
The objective of this study was to compare noncontrast computed tomography (NCCT) and computed tomography perfusion (CTP) in early diagnosis of acute ischemic stroke and to define influence of these diagnostic procedures on early outcome of thrombolytic therapy (TLTH). The study included 45 patients, 35 patients submitted to NCCT and CTP and 10 patients who underwent only NCCT, before CTP was introduced. Based on the National Institute of Health Stroke Scale (NIHSS) score we compared early outcome of patients who received TLTH after NCCT only (group 1) with the early outcome of patients who received TLTH following NCCT and CTP (group 2). Statistically significant difference was found in acute stroke diagnosing between CTP and NCCT (p = 0.002). There were no statistically significant differences in TLTH early outcome between group 1 and group 2. In conclusion, CTP should be done regulary in patients presenting with acute ischemic stroke symptoms. More research needs to be done in defining exact influence of CTP implementation on the TLTH outcome. 相似文献
80.