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Observed Shifts (observed + shift)
Selected AbstractsAggression in imported fire ants: an explanation for shifts in their spatial distributions in Southern United States?ECOLOGICAL ENTOMOLOGY, Issue 4 2009HENRY Y. FADAMIRO Abstract 1.,The imported fire ants, Solenopsis invicta Buren (red), S. richteri Forel (black), and their hybrids (S. invicta × S. richteri) are sympatric congeners with overlapping but shifting spatial distributions in northern Alabama and Mississippi, United States. 2.,The abilities of workers of the three ant forms (or species) to recognise non-nestmate conspecifics and heterospecifics were compared in separate aggression bioassays using three group sizes of competitor numbers (battles): 1-1, 5-1, and 5-5 resident,intruder battles. 3.,Workers of all three forms showed significant aggression toward non-nestmate conspecifics and heterospecifics. The results of the intra-specific aggression bioassays showed that S. invicta had the lowest aggression threshold, whereas S. richteri was the least aggressive. Survival rates 1 day after intra-specific encounters were higher for S. richteri than for S. invicta or hybrids, consistent with its lower aggressiveness. 4.,In inter-specific interactions, S. invicta workers showed the greatest aggression and were more aggressive towards S. richteri than to hybrids. Furthermore, survival 1 day after inter-specific encounters was highest for S. invicta workers, whether they were the intruders or residents. The hybrid form was intermediate between both parental forms in aggression and post-aggression survival. 5.,The live 1-1 and 5-5 battles produced similar and consistent results, but differences were amplified in the 5-5 battles, suggesting an effect of group size on aggression. These results may explain the observed shifts in the spatial distributions of the three forms and range restriction of S. richteri in southern United States. [source] NMR Characterization of Complex p- Oligophenyl Scaffolds by Means of Aliasing Techniques to Obtain Resolution-Enhanced Two-Dimensional SpectraHELVETICA CHIMICA ACTA, Issue 9 2004Damien Jeannerat The usefulness of computer-assisted aliasing to secure maximal resolution of signal clusters in 1H- and 13C-NMR spectra (which is essential for structure determination by HMBC 2D NMR spectroscopy) in minimal acquisition time is exemplified by the complete characterization of the two complementary p -octiphenyls 1 and 2 with complex substitution patterns. The need for digital resolution near 1,Hz/pt to dissect the extensive signal clusters in the NMR spectra of these refined oligomers excluded structure determination under routine conditions. High resolution was secured by exploiting the low signal density in the 13C dimension of HMBC spectra by using computer-assisted aliasing to maximize signal density. Based on the observed shifts in DEPT and 1H-decoupled 13C-NMR spectra of 1 and 2, computer-assisted aliasing allowed to reduce the number of required time increments by a factor of 20 to 30 compared to full-width spectra with identical resolution. Without signal-to-noise constraints, this computer-assisted aliasing reduced the acquisition time for high-resolution NMR spectra needed for complete characterization of refined oligomers 1 and 2 by the same factor (e.g., from over a day to about an hour). With resolved signal clusters in fully aliased HSQC and HMBC spectra, unproblematic structure determination of 1 and 2 is demonstrated by unambiguous assignment of all C- and H-atoms. These findings demonstrate that computer-assisted aliasing of the underexploited 13C dimension makes extensive molecular complexity accessible by conventional multidimensional heteronuclear NMR experiments without extraordinary efforts. [source] Assessing the impact of deforestation and climate change on the range size and environmental niche of bird species in the Atlantic forests, BrazilJOURNAL OF BIOGEOGRAPHY, Issue 7 2010Bette A. Loiselle Abstract Aim, Habitat loss and climate change are two major drivers of biological diversity. Here we quantify how deforestation has already changed, and how future climate scenarios may change, environmental conditions within the highly disturbed Atlantic forests of Brazil. We also examine how environmental conditions have been altered within the range of selected bird species. Location, Atlantic forests of south-eastern Brazil. Methods, The historical distribution of 21 bird species was estimated using Maxent. After superimposing the present-day forest cover, we examined the environmental niches hypothesized to be occupied by these birds pre- and post-deforestation using environmental niche factor analysis (ENFA). ENFA was also used to compare conditions in the entire Atlantic forest ecosystem pre- and post-deforestation. The relative influence of land use and climate change on environmental conditions was examined using analysis of similarity and principal components analysis. Results, Deforestation in the region has resulted in a decrease in suitable habitat of between 78% and 93% for the Atlantic forest birds included here. Further, Atlantic forest birds today experience generally wetter and less seasonal forest environments than they did historically. Models of future environmental conditions within forest remnants suggest generally warmer conditions and lower annual variation in rainfall due to greater precipitation in the driest quarter of the year. We found that deforestation resulted in a greater divergence of environmental conditions within Atlantic forests than that predicted by climate change. Main conclusions, The changes in environmental conditions that have occurred with large-scale deforestation suggest that selective regimes may have shifted and, as a consequence, spatial patterns of intra-specific variation in morphology, behaviour and genes have probably been altered. Although the observed shifts in available environmental conditions resulting from deforestation are greater than those predicted by climate change, the latter will result in novel environments that exceed temperatures in any present-day climates and may lead to biotic attrition unless organisms can adapt to these warmer conditions. Conserving intra-specific diversity over the long term will require considering both how changes in the recent past have influenced contemporary populations and the impact of future environmental change. [source] Correlation optimized warping and dynamic time warping as preprocessing methods for chromatographic dataJOURNAL OF CHEMOMETRICS, Issue 5 2004Giorgio Tomasi Abstract Two different algorithms for time-alignment as a preprocessing step in linear factor models are studied. Correlation optimized warping and dynamic time warping are both presented in the literature as methods that can eliminate shift-related artifacts from measurements by correcting a sample vector towards a reference. In this study both the theoretical properties and the practical implications of using signal warping as preprocessing for chromatographic data are investigated. The connection between the two algorithms is also discussed. The findings are illustrated by means of a case study of principal component analysis on a real data set, including manifest retention time artifacts, of extracts from coffee samples stored under different packaging conditions for varying storage times. We concluded that for the data presented here dynamic time warping with rigid slope constraints and correlation optimized warping are superior to unconstrained dynamic time warping; both considerably simplify interpretation of the factor model results. Unconstrained dynamic time warping was found to be too flexible for this chromatographic data set, resulting in an overcompensation of the observed shifts and suggesting the unsuitability of this preprocessing method for this type of signals. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||