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81.
82.
The Devonian plant fossil Protosalvinia (Foerstia) has been examined by solid-state 13C nuclear magnetic resonance spectroscopy (NMR) and pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). Results of these studies reveal that the chemical structure of Protosalvinia is remarkably similar to that of coalified wood. A well-defined phenolic carbon peak in the NMR spectra and the appearance of phenol and alkylated phenols in pyrolysis products are clearly indicative of lignin-like compounds. These data represent significant new information on the chemical nature of Protosalvinia and provide the first substantial organic geochemical evidence for land plant affinity. ▭ Protosalvinia, Foerstia, Upper Devonian, biostratigraphy, carbon-13 NMR, PY-GC-MS, lignin.  相似文献   
83.
84.
In this paper, we report the isolation of 11 polymorphic microsatellite loci from Lithophragma maximum (Saxifragaceae), a rare species restricted to San Clemente Island, California. We found moderate levels of allelic variation (mean NA= 5.5) and high levels of expected heterozygosity (mean HE= 0.531) across sampled individuals. However, eight loci showed a significant absence of heterozygous individuals, which we attribute to small population size and demographic history of the species.  相似文献   
85.
ABSTRACT One of the largest known populations of the federally endangered southwestern willow flycatcher (Empidonax traillii extimus) occurs at Roosevelt Lake, Arizona, USA. Modifications to Roosevelt Dam, completed in 1996, raised the height of the dam and resulted in a high probability of willow flycatcher habitat inundation within the reservoir's conservation pool. We collected habitat measurements and monitored 922 willow flycatcher nests from 1996 to 2006 to investigate effects of inundation on willow flycatcher habitat and subsequent changes in nest success, productivity, and distribution. Inundation of willow flycatcher habitat at Roosevelt Lake occurred in 2005, changing the location and amount of suitable breeding habitat and significantly altering habitat structure (e.g., thinner vegetation, more canopy gaps) of formally occupied nest sites. The willow flycatcher population at Roosevelt Lake decreased 47% from 209 territories in 2004 to 111 territories in 2006 in response to habitat changes. Willow flycatchers made fewer nesting attempts and nest success rates were significantly lower during inundation (2005 and 2006: 45%) than preinundation (1996–2004: 57%). Combined, these factors negatively affected the population's productivity during inundation. Although inundation caused extensive vegetation die-off, we did observe regeneration of vegetation in some areas at Roosevelt Lake in 2006. The Roosevelt Lake population remains one of the largest willow flycatcher populations in the state and territory numbers remain high enough that the population may not suffer long-term effects if sufficient suitable habitat continues to exist during the cycle of inundation and regeneration. Reservoir managers may be able to develop dam management guidelines that reduce damage to habitat, encourage habitat growth, and mimic the dynamic nature of unaltered riparian habitat. These guidelines can be implemented, as appropriate, at reservoirs throughout the willow flycatcher's range.  相似文献   
86.
We have isolated and characterized five microsatellite loci from Rhizopogon occidentalis and six loci from Rhizopogon vulgaris (Boletales, Basidiomycota). Microsatellite variation was assessed using 32 R. occidentalis and 48 R. vulgaris individuals from four populations in California. The number of alleles across populations ranged from two to 10 for R. occidentalis and three to eight for R. vulgaris. Expected heterozygosity values within populations ranged from 0.00 to 0.85 for R. occidentalis and 0.00 to 0.75 for R. vulgaris. These are the first microsatellite loci isolated for R. occidentalis and R. vulgaris and will be useful in the examination of their population genetic structure.  相似文献   
87.

Background

Association of genetic-variants in the FADS1-FADS2-gene-cluster with fatty-acid-composition in blood of adult-populations is well established. We analyze this genetic-association in two children-cohort-studies. In addition, the association between variants in the FADS-gene-cluster and blood-fatty-acid-composition with eczema was studied.

Methods and Principal Findings

Data of two population-based-birth-cohorts in the Netherlands and Germany (KOALA, LISA) were pooled (n = 879) and analyzed by (logistic) regression regarding the mutual influence of single-nucleotide-polymorphisms (SNPs) in the FADS-gene-cluster (rs174545, rs174546, rs174556, rs174561, rs3834458), on polyunsaturated fatty acids (PUFA) in blood and parent-reported eczema until the age of 2 years. All SNPs were highly significantly associated with all PUFAs except for alpha-linolenic-acid and eicosapentaenoic-acid, also after correction for multiple-testing. All tested SNPs showed associations with eczema in the LISA-study, but not in the KOALA-study. None of the PUFAs was significantly associated with eczema neither in the pooled nor in the analyses stratified by study-cohort.

Conclusions and Significance

PUFA-composition in young children''s blood is under strong control of the FADS-gene-cluster. Inconsistent results were found for a link between these genetic-variants with eczema. PUFA in blood was not associated with eczema. Thus the hypothesis of an inflammatory-link between PUFA and eczema by the metabolic-pathway of LC-PUFAs as precursors for inflammatory prostaglandins and leukotrienes could not be confirmed by these data.  相似文献   
88.
89.
Analyses of morphological data on the higher-level phylogenetics of Thysanoptera have suggested two alternative hypotheses: (1) sister-taxon status of the monophyletic suborders Terebrantia and Tubulifera. and (2) paraphyly of Terebrantia with respect to Tubulifera. Analyses of nucleotide sequence data from the mitochondrial gene cytochrome oxidase I and the nuclear gene I8S rONA using maximum parsimony. neighbour joining. and maximum likelihood provide strong support for the hypothesis of a sister-taxon relationship between the Terebrantia and Tubulifera. These data resolve this long-standing controversy in thysanopteran phylogenetics and provide a framework for further studies of higher-level relationships in this order.  相似文献   
90.
Records of effects of ambient ozone pollution on vegetation have been compiled for Europe for the years 1990–2006. Sources include scientific papers, conference proceedings, reports to research funders, records of confirmed ozone injury symptoms and an international biomonitoring experiment coordinated by the ICP Vegetation. The latter involved ozone‐sensitive (NC‐S) and ozone‐resistant (NC‐R) biotypes of white clover (Trifolium repens L.) grown according to a common protocol and monitored for ozone injury and biomass differences in 17 European countries, from 1996 to 2006. Effects were separated into visible injury or growth/yield reduction. Of the 644 records of visible injury, 39% were for crops (27 species), 38.1% were for (semi‐) natural vegetation (95 species) and 22.9% were for shrubs (49 species). Owing to inconsistencies in reporting effort from year to year it was not possible to determine geographical or temporal trends in the data. Nevertheless, this study has shown effects in ambient air in 18 European countries from Sweden in the north to Greece in the south. These effects data were superimposed on AOT40 (accumulated ozone concentrations over 40 ppb) and POD3gen (modelled accumulated stomatal flux over a threshold of 3 nmol m?2 s?1) maps generated by the EMEP Eulerian model (50 km × 50 km grid) that were parameterized for a generic crop based on wheat and NC‐S/NC‐R white clover. Many effects were found in areas where the AOT40 (crops) was below the critical level of 3 ppm h. In contrast, the majority of effects were detected in grid squares where POD3gen (crops) were in the mid‐high range (>12 mmol m?2). Overall, maps based on POD3gen provided better fit to the effects data than those based on AOT40, with the POD3gen model for clover fitting the clover effects data better than that for a generic crop.  相似文献   
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