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排序方式: 共有166条查询结果,搜索用时 15 毫秒
81.
ADAM J. VANBERGEN BEN A. WOODCOCK MATTI KOIVULA JARI NIEMELÄ D. JOHAN KOTZE TOM BOLGER VALERIE GOLDEN FLORENCE DUBS GUILLAUME BOULANGER JOSE SERRANO JOSÉ LUÍS LENCINA ARTUR SERRANO CARLOS AGUIAR ANNE‐CATHERINE GRANDCHAMP SILVIA STOFER GYÖZÖ SZÉL EVA IVITS PETRA ADLER JOCHUM MARKUS ALLAN D. WATT 《Ecological Entomology》2010,35(2):226-235
1. Anthropogenic pressures have produced heterogeneous landscapes expected to influence diversity differently across trophic levels and spatial scales. 2. We tested how activity density and species richness of carabid trophic groups responded to local habitat and landscape structure (forest percentage cover and habitat richness) in 48 landscape parcels (1 km2) across eight European countries. 3. Local habitat affected activity density, but not species richness, of both trophic groups. Activity densities were greater in rotational cropping compared with other habitats; phytophage densities were also greater in grassland than forest habitats. 4. Controlling for country and habitat effects, we found general trophic group responses to landscape structure. Activity densities of phytophages were positively correlated, and zoophages uncorrelated, with increasing habitat richness. This differential functional group response to landscape structure was consistent across Europe, indicated by a lack of a country × habitat richness interaction. Species richness was unaffected by landscape structure. 5. Phytophage sensitivity to landscape structure may arise from relative dependency on seed from ruderal plants. This trophic adaptation, rare in Carabidae, leads to lower phytophage numbers, increasing vulnerability to demographic and stochastic processes that the greater abundance, species richness, and broader diet of the zoophage group may insure against. 相似文献
82.
YO TOMA FABIÁN G. FERNÁNDEZ SYOHEI SATO MIKI IZUMI RYUSUKE HATANO TOSHIHIKO YAMADA AYA NISHIWAKI GERMÁN BOLLERO J. RYAN STEWART 《Global Change Biology Bioenergy》2011,3(2):116-134
Species in the Miscanthus genus have been proposed as biofuel crops that have potential to mitigate elevated atmospheric carbon dioxide (CO2) levels and nitrous oxide (N2O) and methane (CH4) emissions. Miscanthus sinensis is widespread throughout Japan and has been used for biomass production for centuries. We assessed the carbon (C) budget and N2O and CH4 emissions over the growing season for 2 years in a M. sinensis‐dominated grassland that was naturally established around 1972 in Tomakomai, Hokkaido, Japan, which is near the northern limit for M. sinensis grassland establishment on Andisols. Average C budget was ?0.31 Mg C ha?1, which indicates C was released from the grassland ecosystem to the atmosphere. Dominant components in the C budget appeared to be aboveground net primary production of plants (1.94–2.80 Mg C ha?1) and heterotrophic respiration (2.27–3.11 Mg C ha?1). The measurement of belowground net primary production (BNPP) of plants in the M. sinensis grassland was extremely variable, thus only an approximate value could be calculated. Mean C budget calculated with the approximated BNPP value was 1.47 and ?0.23 Mg C ha?1 for 2008 and 2009, respectively. Given belowground biomass (9.46–9.86 Mg C ha?1) was 3.1–6.5 times higher than that of aboveground biomass may provide additional evidence suggesting this grassland represents a C sink. Average CH4 emissions across years of ?1.34 kg C ha?1 would indicate this grassland acts as an atmospheric CH4 sink. Furthermore, average N2O emissions across years were 0.22 kg N ha?1. While the site may contribute N2O to the atmosphere, this value is lower compared with other grassland types. Global warming potential calculated with the approximated BNPP value was ?5.40 and 0.95 Mg CO2 Eq ha?1 for 2008 and 2009, respectively, and indicates this grassland could contribute to mitigation of global warming. 相似文献
83.
JOSE MARIA PONS ENRIC VICENS FETTOUMA CHIKHI‐AOUIMEUR HASSEN ABDALLAH 《Palaeontology》2012,55(3):677-695
Abstract: The revision of the radiolitid rudist bivalve Praeradiolites biskraensis (Coquand), including shell morphology and structure, taxonomical status, and palaeogeographical and stratigraphical distribution, was undertaken. We studied Coquand’s collection, other specimens from the type locality, Col de Sfa, and other Algerian fossil localities, as well as recently collected material from the Gafsa region in Tunisia. A neotype from Col de Sfa is proposed. The stratigraphical distribution of the species is bracketed in the Upper Cenomanian, using the distribution of co‐occurring ammonites in Tunisia and microfossils in Algeria. The palaeogeographical distribution is verified for Algeria and Tunisia based on all records in North Africa. Survey of the taxonomical status and problems of related radiolitid genera has resulted in revised diagnoses of Praeradiolites Douvillé, Eoradiolites Douvillé, Sphaerulites Lamarck and Radiolites Lamarck and revealed problems with Radiolites fleuriaui d’Orbigny, which is being the type species of Praeradiolites. Maghrebites gen. nov. is proposed for the North African radiolitid rudist Praeradiolites biskraensis (Coquand). 相似文献
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87.
ENRIQUE E. MONTAMAT SANDRA DURAND JOSE L. BOCCO GLORIA M. DE LUCA D'ORO ANTONIO BLANCO 《The Journal of eukaryotic microbiology》1999,46(2):155-159
Analysis of zymograms of extracts of Trypanosoma cruzi isolated from different hosts in Argentina allowed characterization of 12 zymodemes or "isozymic strains," only six of which were found in human patients. Two of these six zymodemes (Z1 and Z12) were widely distributed and found in more than 80% of human patients. These two "major natural clones" differed significantly in pathogenic activity. Because the groupings obtained by studying enzymes and kinetoplast DNA (kDNA) were similar, it is possible to identify the zymodeme by analyzing kDNA. A 290-bp fragment was amplified by PCR using primers for the sequences flanking the hypervariable regions of kDNA minicircles. Labeled probes for this fragment, prepared from Z1 and Z12 reference stocks, hybridized specifically with PCR-amplified kDNA from parasite stocks, allowing identification of zymodemes. 相似文献
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89.
CHRISTOPHER B. ANDERSON JUAN L. CELIS‐DIEZ BARBARA J. BOND GUILLERMO MARTÍNEZ PASTUR CHRISTIAN LITTLE JUAN J. ARMESTO CLAUDIO GHERSA AMY AUSTIN TOMAS SCHLICHTER ANTONIO LARA MARTIN CARMONA ENRIQUE J. CHANETON JULIO R. GUTIERREZ RICARDO ROZZI KRISTIN VANDERBILT GUILLERMO OYARCE ROBERTO J. FERNÁNDEZ 《Austral ecology》2012,37(5):529-536
90.
CAROLIN A. REBERNIG GERALD M. SCHNEEWEISS KATHARINA E. BARDY PETER SCHÖNSWETTER JOSE L. VILLASEÑOR RENATE OBERMAYER TOD F. STUESSY HANNA WEISS‐SCHNEEWEISS 《Molecular ecology》2010,19(16):3421-3443
Pleistocene climatic fluctuations had major impacts on desert biota in southwestern North America. During cooler and wetter periods, drought‐adapted species were isolated into refugia, in contrast to expansion of their ranges during the massive aridification in the Holocene. Here, we use Melampodium leucanthum (Asteraceae), a species of the North American desert and semi‐desert regions, to investigate the impact of major aridification in southwestern North America on phylogeography and evolution in a widespread and abundant drought‐adapted plant species. The evidence for three separate Pleistocene refugia at different time levels suggests that this species responded to the Quaternary climatic oscillations in a cyclic manner. In the Holocene, once differentiated lineages came into secondary contact and intermixed, but these range expansions did not follow the eastwardly progressing aridification, but instead occurred independently out of separate Pleistocene refugia. As found in other desert biota, the Continental Divide has acted as a major migration barrier for M. leucanthum since the Pleistocene. Despite being geographically restricted to the eastern part of the species’ distribution, autotetraploids in M. leucanthum originated multiple times and do not form a genetically cohesive group. 相似文献