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1.
The “false head” hypothesis states that due to the posterior ventral wing markings of certain butterflies which resemble a “false head,” visually hunting predators, such as birds, are deceived into attacking the hind wing area rather than the true head of the butterfly. In the laboratory, six groups of artificially marked dead cabbage butterflies, Pieris rapae, were presented to Blue Jays, Cyanocitta cristata. Of the six “false head” markings, only the eyespot significantly influenced the point of attack. All of the “false head” markings, however, led to a greater proportion of attacks to the hind wing area of the butterfly. In the course of prey handling following an initial attack, each of the six “false head” markings significantly directed predator handling strikes away from the true head of captive butterflies to the anal angle of the hind wing. In a second experiment, live P. rapae with “false head” markings were mishandled and thus escaped, significantly more frequently than controls. Therefore, “false head” markings may confer a selective advantage by increasing the probability of escape, particularly during handling.  相似文献   

2.
I respond to two of the main arguments in Rosenberg’s commentary on “Mind, Matter, and Metabolism.” Rosenberg’s claim that metabolic activities are “modularized” in a way that sets them apart from cognitive processes is not true given the broad sense of the “metabolic” employed in my paper, and contemporary neuroscience, including the work on navigation cited by Rosenberg, has begun to yield an understanding of subjectivity and “point of view.”  相似文献   

3.
The hypothesized sexual difference in the incidence of torus mandibularis in Eskimoid groups, as well as age and group differences, was studied in two Northwest Territories Eskimo groups and in an Aleut group (examined by Moorrees). The data were analyzed using statistical methods new to the field of anthropology. The method analyzes data sampled from a multinomial distribution. A hierarchy of log linear models are fitted to the cell counts of a contingency table. An iterative proportional fitting procedure is used to obtain expected cell counts under each log linear model. The “goodness of fit” of each model is tested by the log likelihood ratio. This statistic can be partitioned into additive components such that differences between models can be tested. In this way a “best” model, from the hierarchy of models, is chosen. Among these three groups of Eskimos, the incidence of torus mandibularis was not affected by sex but was affected by age and was different between the three groups.  相似文献   

4.
The objective of the study was to provide a general procedure for mapping species abundance when data are zero‐inflated and spatially correlated counts. The bivalve species Macoma balthica was observed on a 500×500 m grid in the Dutch part of the Wadden Sea. In total, 66% of the 3451 counts were zeros. A zero‐inflated Poisson mixture model was used to relate counts to environmental covariates. Two models were considered, one with relatively fewer covariates (model “small”) than the other (model “large”). The models contained two processes: a Bernoulli (species prevalence) and a Poisson (species intensity, when the Bernoulli process predicts presence). The model was used to make predictions for sites where only environmental data are available. Predicted prevalences and intensities show that the model “small” predicts lower mean prevalence and higher mean intensity, than the model “large”. Yet, the product of prevalence and intensity, which might be called the unconditional intensity, is very similar. Cross‐validation showed that the model “small” performed slightly better, but the difference was small. The proposed methodology might be generally applicable, but is computer intensive.  相似文献   

5.
A numerical taxonomic study of Caprifoliaceae is presented. For the sake of analyzing the resemblances between the 33 species or OUT’s selected at random from the total 13 genera of the family, a summation of 32 characters was employed in the numerical analyses. Raw data for each character were given equal weighting by condensation in order to have adequate comparisons, and the characters were converted to 51 states, each with a new range of zero to one. Owing to the lack of sufficient data from other lines for numerical analyses, the characters used in this study were largely morphological. The estimation of the coefficient resemblance between each pair or OUT’s was established using the association coefficient method. The resulting values comprise the 33×33 OUT’s basic similarity matrix. The clustering technique used was unweighted pair-group method using arithmetic averages (UPGMA). It can be stated that the scheme of phenetic relationships shown in the resultant dendrogram (Fig. 1) is on the whole in accord with the concepts hold by most current taxonomists, but with some noteworthy exceptions. If the phenon line of tribal demarkation is drawn at the level of 0.6820, the OUT’s could be roughly divided into five groups or tribes. The fact that the highest degree of correlation between Group I Sambuceae and Group II Viburneae on the one hand, and the great distance between them and the rest genera of the family on the other hand agrees well with the data obtained from morphological (Troll and Weberling, 1966), anatomical (Wilkinson, 1949, Metcalfe and Chalk, 1950), embryological (Moissl, 1941), sereological (Hillebrand and Fairbrother, 1970), and phytochemical (Bohm and Glennie, 1971) researches. These two tribes are most probably members of different phylogenetic origin. Triosteum and Symphoricarpos both show their affinities with Leycesteria of Group V Lonicereae instead of Group III Linnaeea or Group II Viburneae as suggested by some taxonomists, and thus supports the opinion of Troll and Weberling (1966), who suggested that these two genera are members of the tribe Lonicereae. The location of the phylogenetically uncertain genus Heptacodium in the dendrogram shows its close morphological similarity to the tribe Linnaeeae. Because of the relatively small number of characters considered in this work, and “taxonomic judgement” was used in selecting these characters which appeared to be most “basic” to the classification of genera in the family, as well as the limitation of numerical taxonomy in itself, the resultant scheme of tribal relationships presented in this paper is by no means phylogenetic, but one that provides an excellent checkon ordinary taxonomic procedures.  相似文献   

6.
A solution algorithm yielding the pressure and flow-rate distributions for steady flow in an arbitrary, tree-like network is provided. Given the tree topology, the conductance of each segment and the pressure distribution at the boundary nodes, the solution is obtained from a simple recursion based on perfect Gauss elimination. An iterative solution method using this algorithm is suggested to solve for the pressure and flow-rate distributions in an arbitrary diverging-converging (arterial-venous) network consisting of two tree-like networks which are connected to each other at the capillary nodes. A number of special solutions for tree-like networks are obtained for which the general algorithm is either simplified or can be replaced by closed form solutions of the pressure and flow-rate distributions. These special solutions can also be obtained for each tree of diverging-converging networks having particular topologies and conductance distributions. Sample numerical results are provided.  相似文献   

7.
A solution is presented for the problem of how to find ancestral codons which minimize the number of mutations over a given network of species for which character-states of aligned amino acid sequences among the contemporary species are known. Three theorems which allow this “maximum parsimony” problem to be solved are proved; then the use of these theorems in finding maximum parsimony ancestral codons is illustrated on a network of chicken and mammalian alpha globin amino acid sequences at two alignment positions.  相似文献   

8.
Most of the common and dominant tree species in gaps of a climax Japanese beech (Fagus crenata) forest have large seedling banks on the forest floor. These seedlings were classified into “true seedlings” and “seedling sprouts”, each of which was further classified into two and three subtypes, respectively. Each species had a characteristic seedling form spectrum. The seedling bank of beech was composed almost solely of true seedlings, whereas, seedling sprouts predominated in the seedling banks of lower tree species such as Prunus grayana Maxim. and some species of Acer. The age structures suggested that seedling sprouts had longer life spans and had been recruited more constantly than true seedlings. The habit of sprouting and creeping seemed to enable seedlings of these species to persist for long periods, thus increasing their chance for eventual success in canopy gaps.  相似文献   

9.
The classical immunological paradigm is predicated on the body's ability to recognize and eliminate “nonself.” However, the “self–nonself” model has yet to facilitate any resolution of the field's major concerns, and may thus prove to be of limited use. Merely discarding it is no solution, as the juxtaposition of “self” and “nonself” persists in research, in clinical settings, and in everyday practice despite the best efforts of theoretical immunologists. Instead, the very conception of “selfhood” may prove to be key. Replacing immunology's prior and persistent “self” with less static concepts derived from non-Western contexts not only resolves immunology's famous paradoxes but also offers a new and more accurate model that allows immunology to reframe what may become an outmoded Enlightenment construct of “self.” In such a new paradigm, immunology's well-known system of protection and defense is replaced with a view in which nonself becomes less the body's enemy than its primary mechanism for the creative assimilation of difference. This incorporative model—in which the “immune system” functions more as a search engine than as an expeller of difference—both resolves outstanding paradoxes, and complies more accurately with contemporary knowledge and research practice.  相似文献   

10.
Abstract

We analysed the effects of patch size and isolation on vascular plants in Quercus cerris forest surrounding Rome (Italy). We randomly sampled 96 plots within 18 forest patches with homogeneous environmental variables; the patches ranged from 1.4 ha to 424.5 ha and were divided into four size classes. We performed the analyses at the patch level using linear regression. At the size class level, the analysis of species richness response to fragmentation (area effect) was performed with ANOVA, while the effect on community composition was analysed by means of PERMANOVA. We also investigated which species could be used as indicator species for each size class. Lastly, to evaluate the advantages of conserving several small patches as opposed to few large ones, we used a cumulative area approach ranking forest fragments. The correlation between species richness and patch area was positive, with a significant difference between the “large” and “small” size classes, while analysis on community composition showed that “large” versus “medium” and “large” versus “small” were significantly different. Nemoral species were recognised as indicators in the “large” class, and shrub and edge species in the “small” class. Our results indicate that 10 ha may be a suitable forest size threshold for planning and conservation.  相似文献   

11.
《Ecological Complexity》2007,4(1-2):48-57
An important question in the network representation of ecological systems is to determine how direct and indirect interactions between species determine the positional importance of species in the ecosystem. Here we present a quantitative analysis of the similarities and differences of six different topological centrality measures as indicators of keystone species in 17 food webs. These indicators account for local, global and “meso-scale” – intermediate between local and global – topological information about species in the food webs. Using factor analysis we shown that most of these centrality indices share a great deal of topological information, which range from 75% to 96%. A generalized keystone indicator is then proposed by considering the factor loadings of the six-centrality measures, which contains most of the information encoded by these indices. However, the individual ordering of species according to these criteria display significant differences in most food webs. We simulate the effects of species extinction by removing species ranked according to a local and a “meso-scale” centrality indicator. The differences observed on three network characteristics – size, average distance and clustering coefficient of the largest component – after the removal of the most central nodes indicate that the consideration of these indices have different impacts for the ranking of species with conservational biology purposes. The “meso-scale” indicator appears to play an important role in determining the relative importance of species in epidemic spread and parasitism rates.  相似文献   

12.
The present paper deals mainly with the karyotype analysis of five materials in Angelica dahurica collected in Yanbian of Jilin, Anguo of Hebei, Yuxian of Henan, Hangzhou of Zhejiang and Suining of Sichuan. They are under the names “Dongbeidahuo”, “Qibaizhi”, “Yubaizhi”, ”Hangbaizhi” and “Chuanbaizhi” respectively. Among then “Dongbeidahuo” is a wild plant, which occurs in northeastern China, and the others are cultivated as important crude drugs in some provinces. “Qi-Baizhi” and “Yubaizhi” have been identified as conspecific with the wild Baizhi-“Do-Ngbeidahuo” (A. dahurica) according to the external morphological features, whereas the other cultivated ones, “Hangbaizhi” and “Chuanbaizhi”, treated as a variety (A. dahurica var. formosana). The results of karyotype analysis are shown in Plate 1, 2, with the formula 2n=22 =12 m+2 mSAT+4sm+4st. The karyotypes described here are constantly characterized by satellites attached to the fourth pair of metacentric chromosomes and differ from the published reports on the other species of the genus. It is reasonable to say that the five materials collectively named “Baizhi” are taxonomically closely related to each other and could be regarded as conspecific. Since the second chromosome pair is submetacentric in “Dongbeidahuo”, it may be justifiable to separate the wild plant from the cultivated ones and treat them as two separate varieties.  相似文献   

13.
Mathematical modeling is a convenient way for characterization of complex ecosystems. This approach was applied to study the dynamics of zooplankton in Lake Sevan (Armenia) at different stages of anthropogenic eutrophication with the use of a novel method called discrete modeling of dynamical systems with feedback (DMDS). Simulation demonstrated that the application of this method helps in characterization of inter- and intra-component relationships in a natural ecosystem. This method describes all possible pairwise inter-component relationships like “plus–plus,” “minus–minus,” “plus–minus,” “plus–zero,” “minus–zero,” and “zero–zero” that occur in most ecosystems. Based on the results, a working hypothesis was formulated. It was found that the sensitivity to weak external influence in zooplanktons was the greatest during the mid period of eutrophication in Lake Sevan, whereas in the final stages of eutrophication, an outbreak in the biomass production of cyanobacteria was evident. To support this approach, a weak external disturbance in the form of magnetic storm was used to see its effect on species Daphnia longispina sevanica. A statistically significant correlation between the frequency of magnetic storms and the number of this species was revealed and an increase in the number of toxic cyanobacteria species as a consequence of eutrophication. This paper, for the first time, suggests a DMDS method, to diagnose impact of anthropogenic eutrophication on environment.  相似文献   

14.
The treatment advocated requires coding of every multistate character in additive binary form and accepts, but does not require, assignment of direction to the transformations. For each binary character is computed the ratio of the number of incompatibilities observed to the number of incompatibilities expected on the null hypothesis of the random distribution of its states. At this stage the 'noisy' characters are identified by their high ratios. These ratios are used as the basis for selecting a set of core characters common to several large compatible sets (cliques), plus the several characters particular to each large clique, followed by those characters which add further resolution or corroboration with low levels of homoplasy. The 'labelling' procedure of Guise, Peacock & Cleaves (1982) is adapted to identify 'noisy' taxa and individual character scores which are likely to be homoplastic. The procedure facilitates recognition of the robust portions of a dendrogram, alternative further resolutions, and remaining areas of uncertainty.
For the purposes of illustration, data for African toads of the Nectophrynoides lineage are analysed and the resulting dendrogram is plotted on the map of Africa. Some observations are also made on data for lizards of the family Pygopodidae and on birds of the family Alcidae.  相似文献   

15.
Statistically nonsignificant (p > .05) results from a null hypothesis significance test (NHST) are often mistakenly interpreted as evidence that the null hypothesis is true—that there is “no effect” or “no difference.” However, many of these results occur because the study had low statistical power to detect an effect. Power below 50% is common, in which case a result of no statistical significance is more likely to be incorrect than correct. The inference of “no effect” is not valid even if power is high. NHST assumes that the null hypothesis is true; p is the probability of the data under the assumption that there is no effect. A statistical test cannot confirm what it assumes. These incorrect statistical inferences could be eliminated if decisions based on p values were replaced by a biological evaluation of effect sizes and their confidence intervals. For a single study, the observed effect size is the best estimate of the population effect size, regardless of the p value. Unlike p values, confidence intervals provide information about the precision of the observed effect. In the biomedical and pharmacology literature, methods have been developed to evaluate whether effects are “equivalent,” rather than zero, as tested with NHST. These methods could be used by biological anthropologists to evaluate the presence or absence of meaningful biological effects. Most of what appears to be known about no difference or no effect between sexes, between populations, between treatments, and other circumstances in the biological anthropology literature is based on invalid statistical inference.  相似文献   

16.
In flowers of Heliotropium s.l. the primary carpel tips are overtopped by commissural outgrowths. Therefore the stylar cleft mimics a lateral orientation of the carpels. In species in which the fruit splits into four diaspores the separation tissues run through both the median and the transverse fruit planes. In species where only two two-seeded nutlets are developed the fruit splits within the false septa and each half is composed of parts of both carpels (“syn-mericarpids”).  相似文献   

17.
Unlike most laboratory studies, rigorous quality assurance/quality control (QA/QC) procedures may be lacking in ecosystem restoration (“ecorestoration”) projects, despite legislative mandates in the United States. This is due, in part, to ecorestoration specialists making the false assumption that some types of data (e.g. discrete variables such as species identification and abundance classes) are not subject to evaluations of data quality. Moreover, emergent behavior manifested by complex, adapting, and nonlinear organizations responsible for monitoring the success of ecorestoration projects tend to unconsciously minimize disorder, QA/QC being an activity perceived as creating disorder. We discuss similarities and differences in assessing precision and accuracy for field and laboratory data. Although the concepts for assessing precision and accuracy of ecorestoration field data are conceptually the same as laboratory data, the manner in which these data quality attributes are assessed is different. From a sample analysis perspective, a field crew is comparable to a laboratory instrument that requires regular “recalibration,” with results obtained by experts at the same plot treated as laboratory calibration standards. Unlike laboratory standards and reference materials, the “true” value for many field variables is commonly unknown. In the laboratory, specific QA/QC samples assess error for each aspect of the measurement process, whereas field revisits assess precision and accuracy of the entire data collection process following initial calibration. Rigorous QA/QC data in an ecorestoration project are essential for evaluating the success of a project, and they provide the only objective “legacy” of the dataset for potential legal challenges and future uses.  相似文献   

18.
From previously published data, 73 characteristics of 17 species of Chlorococcum were compiled. Comparisons of character states of each character were made, and simple matching coefficients were calculated for each species by following the procedure of Sokal & Michener. From a data matrix of the matching coefficients, a phenogram was constructed according to the unweighted pair group method of Sokal & Sneath. Arithmetic averages were used in transferring data from one matrix to another. The frequency of each character state was calculated, and the character states of the highest frequency (the modes) were used to describe a “typical” Chlorococcum species. Comparisons were made between the “typical” Chlorococcum species and each of the 17 species studied. Simple matching coefficients were also calculated from these comparisons. All of the species had a relatively high affinity for the data of the calculated “typical”. Suggestions are made about the use of a “typical” taxonomic unit, and questions are raised about the taxonomic relationship among species of the genus Tetracystis and the genus Chlorococcum.  相似文献   

19.
“Ecological topology” has recently been highlighted as a “frontier of ecology,” yet the term “ecological topology” only occasionally appears in the literature. On the other hand, the term “topology” appears in a variety of publications in this and other ecologically oriented journals, but its use is varied and applied to a wide cross-section of ecological problems. These variable usages suggest that topology does not have a common meaning to all ecologists. Part of this confusion results from the fact that topological ways of seeing nature are both formally derived from mathematical origins, and informally derived from non-mathematical conceptualizations. Interestingly, parallels occur between both mathematically originated and conceptually originated topology with respect to object-oriented, network topologies (formally derived from Eulerian mathematics), and field-oriented, manifold topologies (formally derived from Poincaréian mathematics). Topological ways of understanding nature and addressing both theoretical and applied problems have served ecology well in the past, but this approach will be improved with a better, more unified understanding among ecologists as to the variety of meanings found and practiced in the science.  相似文献   

20.
Proteins in the molten globule state contain high levels of secondary structure, as well as a rudimentary, nativelike tertiary topology. Thus, the structural similarity between the molten globule and native proteins may have a significant bearing in understanding the protein-folding problem. To explore the nature of side-chain--side-chain interactions in the alpha-lactalbumin (alpha-LA) molten globule, we determined the effective concentration for formation of the 28--111 disulfide bond in 14 double-mutant proteins, each containing two hydrophobic core residues replaced by alanine. We compared our results with those of single-alanine substitutions using the framework of double-mutant cycle analysis and found that, in the majority of cases, the effects of two alanine substitutions are additive. Based on these results, we propose a model of side-chain-side-chain interactions in the alpha-LA molten globule, which takes into consideration the dynamic nature of this partially folded species.  相似文献   

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