不同放牧强度下冷蒿种群小尺度空间格局

时间、空间格局的发展和维持及其对种群和生态系统的影响一直是生态学研究的中心议题 ,这些问题的核心是观察的尺度怎样影响格局的描述。冷蒿 (Artemisia frigida)种群伴随着典型草原退化演替的各个阶段 ,对其所在群落的结构和功能具有重要的影响。应用 Ripley's K函数以及蒙特卡罗 (Monte Carlo)随机模拟方法 ,定量分析了 4种放牧强度下冷蒿种群在 0～10 0 cm尺度上的空间格局及其随尺度的变化规律 ;研究了放牧对冷蒿种群空间格局的影响以及冷蒿在放牧胁迫下的生态适应对策。并以放牧条件下冷蒿的生活史特征、生态适应对策以及群落内植物种间的相互作用为基础 ,探讨产生和维持这些格局的机理。研究结果表明 :1放牧对冷蒿种群空间格局有显著影响。同一放牧强度下冷蒿种群在不同尺度 (0～ 10 0 cm)上的空间格局存在显著差异 ;2在 0～ 10 0 cm尺度上 ,无牧、轻牧条件下冷蒿种群的空间格局为聚集分布 ;中牧条件下在 0～ 6 0 cm尺度上冷蒿种群的空间格局为聚集分布 ,而在 6 0～ 10 0 cm尺度上为均匀分布 ;重牧条件下在 0～ 72 cm尺度上冷蒿种群的空间格局为聚集分布 ,而在 72～ 10 0 cm尺度上为均匀分布 ,这与其自身的生物学特性和种群对放牧压力的生态适应对策密切相关 ;3放牧活动的加剧改变了群落中的各种     

A multivariate analysis of fatness and relative fat patterning.

Skinfold measurements (triceps, subscapular, suprailiac and medial calf) in four samples (376 boys, 352 girs, 338 men and 380 women from rural Colombia) were subjected to principal components analysis to identify components of obesity and relative fat patterning. Three components emerged which were similar in the four samples: a first component of fatness explaining 70-80% of the variance and two fat pattern components each explaining 10-15% of the variance: trunk-extremity and upper-lower body. Fatness and the trunk-extremity pattern components changed with age in children (7-12 years), but none of the components changed with age in adults (25-60+). The fatter tended to be more patterned in both age groups. Canonical correlation analysis revealed that socioeconomic status was more related to fatness than to patterning. With the exception of brothers, all first degree relatives (sib, parent-off-spring) and spouses were correlated in fatness. Some of the correlations between relatives--usually sibs, but not spouses--were also significant for the pattern components, suggesting a genetic basis for the known stability of this characteristic (Garn, '55a). Principal components analysis is a useful multivariate alternative for quantitative studies of anthropometric patterning.     

Mining pattern of the honeysuckle leaf-minerPhytomyza lonicerae

The mining pattern of the honeysuckle leaf-miner Phytomyza lonicerae which feeds on Lonicera gracilipes was analyzed with special reference to the avoidance of parasitoids' attacks. The leaf-miner makes the linear mine with branches and crosses by turning and branching, off the backtracking mine. Both average numbers of turnings and branchings were about 4. The speed of mining was 1.5 times faster in backtracking than in advancing. The mine width increased as the mining larva grew and total volume of consumed plant tissue was nearly constant independent of variability of the number of turnings and other characteristics of the mine. The majority of larval mortality were due to attacks by parasitoid wasps (Chrysochairs pentheus and Diglyphus minoeus), which locate the present position of leaf-miners, by tracing mine tracks, and wasps attack leaf-miners at a higher rate in backtracking than in advancing. The adaptive significance of branching and crossing by leaf-miners was discussed in terms of the reduction of parasitoids' attacks.     

Diversity of palmar pattern ridge counts in Iranian populations

We analyzed bilateral palmar prints of 3,158 individuals from 13 Iranian populations of diverse origins for palmar pattern ridge counts. Right palms did not show greater counts than the left in the majority of the populations studied. Highly significant interpopulational variation was observed for most palmar areas of both males and females. Dendrograms of males and combined sexes showed a good fit with the ethnohistoric background of the populations studied. The results thus demonstrate variation in the palmar pattern ridge counts of populations of diverse origins and may be used as a good measure of population distance.     

Spatial analysis of density dependent pattern in coniferous forest stands

An investigation of spatial pattern in relatively sparse Pinus ponderosa-P. Jeffreyi stands showed that a simple Poisson model of random distribution described the pattern at 5 to 50 m scales in the denser stands examined when allowance is made for inhibition between nearest neighbors. There is evidence for a clumped distribution in large quadrats for the sparsest stands, which concurs with prior work where a mixed Poisson model was fit to the data. The technique used was innovative in that it involved digitally recording tree locations from high resolution aerial photos, which allowed for the automatic application of several statistical techniques in order to determine how pattern varies with plot density and scale. Point locations were recorded for six 11.3 ha plots in three density regions of a 340 ha study area in northeastern California, USA. The inter-event distance distribution, and one- and two-dimensional power spectra were calculated, and variable quadrat analysis was performed for the data sets. The second order and spectral analyses showed no evidence of a distinctive clumped pattern at any scale, and all analyses showed that the pattern was regular at the scale of the average inter-plant distance in the denser stands. For the sparser stands, the counts in large quadrats did not fit a Poisson distribution, but were better fit by a mixed Poisson model describing aggregated pattern.     

Morphological clues to genetic species: multivariate analysis of greater Galago sibling species

Several studies conducted in diverse fields indicate the presence of a genetic discontinuity within the taxon Galago crassicaudatus E. Geoffroy--the thick-tailed bushbaby. One of these areas is morphology. This contribution details a statistical analysis of skull material classified under this taxon in order 1) to confirm the objective existence of two morphotypes, and 2) to investigate the characters that allow the skull types to be distinguished. Emphasis is placed on multivariate techniques, although univariate and bivariate techniques are included where they are felt to be appropriate. All statistical analyses point to the reality of the morphological discontinuity between the groups. This is true even when size considerations have been reduced by rescaling the data. The results support separation of the populations at a specific level: G. crassicaudatus and G. garnettii. In addition, the structural changes observed in the two taxa--including an increase in overall size in G. crassicaudatus--are indicative of a divergence in preferred habitats: G. garnettii is adapted to more mesic environmental conditions, and to a softer, less fibrous diet than is its more robust sibling.     

Bivariate versus multivariate allometry: A note on a paper by Jungers and German

Jungers and German (1981) found differences when they compared 1) coefficients of allometry from bivariate plots of log measurements versus log body weight with 2) those coefficients from the first principal component of the log measurements excluding body weight. It is argued here that an arbitrary choice of unit for “internal size” is all that separates these coefficients. When the unit is chosen to make internal size isometric with body weight the coefficients agree rather well.     

Multi-species pattern analysis of Mediterranean pastures in three stages of ecological succession

Multi-species patterns were analyzed in three stages of ecological succession in oligotrophic pastures in Central Spain using a new method of analysis. The method is based on plotting the species coordinates of principal components analysis undertaken at different block sizes. It allows the detection of any heterogeneity present and reveals both microtopographical and macrotopographical trends in species patterns.Nomenclature follows Tutin et al., 1964–1980, Flora Europaea.     

Genetic analysis of the wing vein pattern of Drosophila

Summary Of the many mutations known to affect the wing vein pattern we have selected the most extreme in 29 genes for study. Their phenotype can be classified in two major classes: lack-of-veins and excess-of-veins, and in several internally coherent groups. The study of multiple mutant combinations, within groups and between groups, reveals several genetic operations at work in the generation of the vein pattern. The finding that some of these mutations also affect cell proliferation in characteristic ways has prompted a generative model of wing morphogenetic and pattern formation based on cell behaviour properties defined by the corresponding wild-type genes.     

Quadrat variance analysis and pattern development during primary succession

Abstract. The interpretation of Hill's ‘Two Term Local Quadrat Variance’ analysis to detect the scale of spatial pattern in vegetation is improved by an equation that relates the block size of a variance peak to the scale of the pattern that gave rise to it. (Contrary to previous belief, the two are not the same, especially for large block sizes.) Deviations of pattern from a perfectly regular alternation of equally sized gaps and patches of uniform density cause changes in the variance. To aid in the interpretation of these changes, two indices of pattern regularity are proposed, one based on density and one based onpresence/absence, in orderte distinguish the effects of irregularities of patch density from irregularities of patch size and position. These methods are applied to a study of primary succession on glacial moraines near Mt. Robson, British Columbia, Canada, in order to evaluate certain hypotheses about the development of pattern. Other researchers have proposed that during succession, the pattern at first intensifies at the scales initially observed, then as succession proceeds some scales of pattern are lost due to coalescence of patches and eventually the intensity of those that remain decreases as the patterns become more and more irregular. The vegetation on the Mt. Robson moraines confirms this sequence of changes in vegetation pattern, only to the extent that patterns intensify initially in the chronosequence; the number of scales of pattern in the vegetation remains about the same throughout and there is no evidence that the patterns become more irregular. The variance-block size graphs derived from presence / absence data matched those from density data well, indicating that the simpler data, in this case, are almost as informative about pattern as the more detailed data.     

Chemiluminescence intensities and spectra of luminol oxidation by sodium hypochlorite in the presence of hydrogen peroxide

Hydrogen peroxide amplifies the chemiluminescence in the oxidation of luminol by sodium hypochlorite. A linear relationship between concentration of hydrogen peroxide and light intensity was found in the concentration range 5 × 10^?8?7.5 × 10^?6 mol/l. At 7.5 × 10^?6 mol/l H₂O₂ the chemiluminescence is amplified 550—fold. The chemiluminescence spectra of these reactions have a wavelength maximum at 431 nm independent of the concentration of hydrogen peroxide. The results indicate that hydrogen peroxide is a necessary component in the chemiluminescent oxidation of the luminol by sodium hypochlorite.     

秦岭太白红杉种群空间分布格局动态及分形特征研究

采用相邻格子样方法采集数据,应用计盒维数和信息维数研究了太白红杉种群空间格局的分形特征,结果表明,太白红杉种群有较高的计盒维数(1.8087)和信息维数(1.7931),表明其对空间占据程度较高.用分布系数法和Morisita格局指数法检验格局类型,发现不同年龄组太白红杉种群均呈聚集分布.运用Greig-Smith的方法研究格局规模,发现太白红杉种群在128m²和512m²处聚集,不同年龄组在不同规模尺度聚集.以区组分布格局强度(PI)检测聚集强度,发现太白红杉种群格局强度随尺度变化程度较高,个体分布不均匀,随着年龄的增大,其聚集强度呈下降趋势.太白红杉种群的空间分布格局特征是其对严酷生境长期适应的结果.     

The effect of feature selection on multivariate pattern analysis of structural brain MR images

Clinical predictions performed using structural magnetic resonance (MR) images are crucial in neuroimaging studies and can be used as a successful complementary method for clinical decision making. Multivariate pattern analysis (MVPA) is a significant tool that helps correct predictions by exhibiting a compound relationship between disease-related features. In this study, the effectiveness of determining the most relevant features for MVPA of the brain MR images are examined using ReliefF and minimum Redundancy Maximum Relevance (mRMR) algorithms to predict the Alzheimer’s disease (AD), schizophrenia, autism, and attention deficit and hyperactivity disorder (ADHD). Three state-of-the-art MVPA algorithms namely support vector machines (SVM), k-nearest neighbor (kNN) and backpropagation neural network (BP-NN) are employed to analyze the images from five different datasets that include 1390 subjects in total. Feature selection is performed on structural brain features such as volumes and thickness of anatomical structures and selected features are used to compare the effect of feature selection on different MVPA algorithms. Selecting the most relevant features for differentiating images of healthy controls from the diseased subjects using both ReliefF and mRMR methods significantly increased the performance. The most successful MVPA method was SVM for all classification tasks.     

Multiscale analysis of pattern formation via intercellular signalling

Lateral inhibition, a juxtacrine signalling mechanism by which a cell adopting a particular fate inhibits neighbouring cells from doing likewise, has been shown to be a robust mechanism for the formation of fine-grained spatial patterns (in which adjacent cells in developing tissues diverge to achieve contrasting states of differentiation), provided that there is sufficiently strong feedback. The fine-grained nature of these patterns poses problems for analysis via traditional continuum methods since these require that significant variation takes place only over lengthscales much larger than an individual cell and such systems have therefore been investigated primarily using discrete methods. Here, however, we apply a multiscale method to derive systematically a continuum model from the discrete Delta-Notch signalling model of Collier et al. (J.R. Collier, N.A.M. Monk, P.K. Maini, J.H. Lewis, Pattern formation by lateral inhibition with feedback: a mathematical model of Delta-Notch intercellular signalling, J. Theor. Biol., 183, 1996, 429-446) under particular assumptions on the parameters, which we use to analyse the generation of fine-grained patterns. We show that, on the macroscale, the contact-dependent juxtacrine signalling interaction manifests itself as linear diffusion, motivating the use of reaction-diffusion-based models for such cell-signalling systems. We also analyse the travelling-wave behaviour of our system, obtaining good quantitative agreement with the discrete system.     

The method of pattern combination analysis in dermatoglyphics: I. Diversity and sex differences among the regional populations of the Yanadi

A method of pattern combination analysis (PCA) is described. It consists of three categories: Pattern combination types (PCT), Triradial pattern combination types (PCT-tr) and Pattern combination ratios (PCR) with specific reference to ten digits and its several indices. The method has been used to investigate its validity in discriminating subdivided populations among the Yanadi tribe. The results show significant differences and a few unique pattern combinations in monomorphic and trimorphic frequencies and also in triradial pattern combination types, especially observed in IY population. Between the five Yanadi populations, the results obtained in all the categories of pattern combinations, in pattern combination indices, were in agreement with respect to the population structure variables of the five populations. The results also show clear sex differences especially observed in triradial pattern combination types (PCT-tr) and absence of tetramorphic patterns and ratios among females. This method can be further used for studying inheritance of the PCA, inbreeding effects and other issues of statistical distributional pattern and other theoretical and empirical aspects of anthropological genetics.