Gower Index Research Articles

Multivariate study of lice (Insecta: Psocodea: Phthiraptera) assemblages hosted by hummingbirds (Aves: Trochilidae).

Lice were collected from 579 hummingbirds, representing 49 species, in 19 locations in Brazil, Costa Rica, Honduras, Paraguay and Peru, at elevations 0–3000 m above sea level. The following variables were included in an ecological analysis (1) host species' mean body mass, sexual size dimorphism, sexual dichromatism, migratory behaviour and dominance behaviour; (2) mean elevation, mean and predictability of temperature, mean and predictability of precipitation of the host species' geographic area; (3) prevalence and mean abundance of species of lice as measures of infestation. Ordination methods were applied to evaluate data structure. Since the traits are expressed at different scales (nominal, interval and ratio), a principal component analysis based on d-correlations for the traits and a principal coordinates analysis based on the Gower index for species were applied. Lice or louse eggs were found on 80 (13.8%) birds of 22 species. A total of 267 lice of 4 genera, Trochiloecetes, Trochiliphagus, Myrsidea and Leremenopon, were collected, with a total mean intensity of 4.6. There were positive interactions between migration behaviour and infestation indices, with elevational migrants having a higher prevalence and abundance of lice than resident birds. Further, we found weak negative correlations between host body mass and infestation indices and positive correlations between mean elevation and prevalence and abundance of Trochiliphagus. Thus, formerly unknown differences in the ecological characteristics and infestation measures of Trochiliphagus and Trochiloecetes lice were revealed, which allows a better understanding of these associations and their potential impacts on hummingbirds.

Correlating variables with different scale types: A new framework based on matrix comparisons

AbstractEcological variables may be expressed on four basic measurement scales (nominal, ordinal, interval or ratio), whereas circular variables and those combining a nominal state with other scale types are also common. However, existing methods are not suited to calculate correlations between all pairwise combinations of such variables, preventing the application of standard multivariate techniques.The essence of the new approach is to derive a so‐called difference semimatrix for all pairs of observations for each variable, and then to calculate the matrix correlation based on two such semimatrices. The advantage of this function, termedd‐correlation, is that comparisons are made on the same logical basis regardless of the measurement scale, allowing for the use of principal components analysis to visualize interrelationships among many variables simultaneously. Further advantages are that missing values in the data are tolerated and that the Gower index of dissimilarity between objects may also be computed.The use of the method is demonstrated on a small toy matrix, an artificial plant trait matrix and a large dataset summarizing ecological features of all vascular plant species of Sardinia, Italy. The source code in R and FORTRAN, and applications for three different operation systems, are provided for computations with results serving as input for other statistical software.The new computational framework will allow the comparison of any types of ecological traits in a mathematically meaningful manner. This option was not available earlier in the field of multivariate statistics, and the method is expected to receive applications in other subject areas as well in which many objects are described in terms of variables expressed on different measurement scales.

Effects of geological formations and topography on the evolution and diversity of soils

Different soils with various properties and sometimes with different types of limitations can be formed which is necessary to investigate the conditions of soil formation and evolution for their optimal use. In this study, we studied the relationship between soil, topography in terms of slope and elevation, and parent material with the land morphology and physical and chemical properties of soil, how the soil formed and evolved. From 19 control soil profiles, 57 soil samples were obtained from three layers and some soil characteristics including Acidity, Salinity, Gypsum, Lime, Texture and Organic matter were measured. Using NEWHALL software, the soil temperature and moisture regime was determined. To study the conditions of topography, the digital elevation map and slope was prepared, the characteristics of geological formations were determined and based on the Gower index and Jacquard index, the relationship between soil evolution factors with topography and parent materials were studied. The diversity of soils classification was studied using richness, uniformity of Shannon and Simpson indices. Based on the results obtained from Gower and jacquard similarity indices, the effect of topography and parent materials on soil diversity was proved. Soil diversity indices showed an increasing trend from the soil order level to the soil family. The increase in the Richness index was higher at the soil family level, so that the highest soil diversity observed at the soil family level. Also, soil diversity is mainly affected by intrinsic factors and to some extent by environmental factors. Soil profile development is mostly influenced by slope, parent materials and in some areas by groundwater level.

Cluster analysis for slope geotechnical prioritization of intervention for the Estrada de Ferro Vitória-Minas

Abstract This article proposes the geotechnical prioritization of intervention of slopes with landslide scars for the Estrada de Ferro Vitoria-Minas by cluster analysis and also the proposition of a relationship between area and volume in landslide scars. Cluster definition helps the decision-making associated to containment measures, mapping and study of landslides for the Estrada de Ferro Vitoria-Minas. The database is composed of the variables: slope's height, inclination, scar area and scar volume. The distance measure used was Gower's index, with Ward's methods to build the clusters. Eight characteristic groups were identified. It was possible to identify stretches that need attention in relation to the propensity of landslides, such as Group 7, stretches 362+600, 093+xxxE and 419+000. Group 7 presented high values for the scarred area and volume, such as maximum area 9.75 x 104 m2 and minimum area 7.49 x 104 m2, and maximum volume 9.20 x 105 m3 and minimum volume 4.08 x105 m3. Group 7 presented high ranges for slope height and inclination. The set of results about Group 7 can be interpreted as stretches with a predisposition for landslides. In relation to intervention measures, Group 7 presents the sections with priority. The relationship between area and volume of landslide scars obtained by the research was compared with the relationships established in literature.

The extrapolation of soil great groups using multinomial logistic regression at regional scale in arid regions of Iran

Soil information is essential for sustainable management of ecosystems. In many parts of Iran, soil information is either not available or difficult to obtain. Therefore, when no detailed map or soil information is accessible in a region of interest, one way to obtain information is to extrapolate information from other parts having soil information. This study was conducted to determine whether - machine-learning extrapolation method extracted from the reference region, i.e. Zarand can estimate soil classes in the interest region, i.e. Bam and reduce the costs of soil mapping. To identify similarities between reference and interest regions, homology of soil forming factors was determined using Gower's similarity index. Then, the multinomial logistic regression was extracted from the reference region and applied into the interest region to estimate soil classes. Moreover, soil classes were predicted in the interest region using direct soil observations; finally, the accuracy of the soil maps obtained from both methods was assessed. Based on Gower index, the study regions, namely Bam and Zarand, were to some extent similar in term of soil forming factors. The results showed that although the soil map derived from the extrapolation process indicated appropriate spatial coverage of soil classes in the interest area, the resultant predictive map of calibrated-in process was slightly more accurate, i.e. higher κ, lower Brier scores. Acceptable levels of predictive accuracy (60%) were achieved using extrapolated model while costs simultaneously significantly lowered. This study put forward the view that the extrapolation method was quite useful in predicting soil classes within areas where soil mapping by calibrated-in method might be too costly or time consuming or where soil observations may not be sufficient. Nevertheless, this research encouraged us to use extrapolated method to fill the gaps in the present soil map of Iran and to apply it as the base map to increase and improve the efficiency of digital soil mapping.

Bivalves from the tectonic units of eastern Serbia in the context of the Pliensbachian (Early Jurassic) palaeobiogeography of Europe

An increase in interest to the Pliensbachian palaeobiogeography of Europe makes urgent consideration of palaeontological data from the regions not taken into account earlier. The representative bivalve records of eastern Serbia and some other European territories (a total of 88 species belonging to 42 genera) permits quantitative assessment of similarity of the Pliensbachian faunas with the Jaccard Index, the Czekanowski's Quantified Coefficient, and the Gower Index. It is established that the Pliensbachian bivalves of eastern Serbia are most similar to those of Bulgaria and France; the similarity to several other European territories is moderate and surprisingly almost the same. The similarity of the Pliensbachian bivalves between the Danubian and Infra-Getic tectonic units constituting the territory of eastern Serbia is significant. The interpretation of the results of this study in the light of the palaeobiogeographical reconstructions implies that the Northwestern European biochore is heterogeneous because of different similarity of the regions within this unit. The bivalve fauna of Portugal is relatively more distinct from the other territories considered in this study (Germany, England, France, etc.). Eastern Serbia was located at or near the transition between Northwestern European (Boreal) and Mediterranean (Tethyan) biochores, and its bivalve fauna is the most similar to those of Bulgaria and France. The results of the present study also show that ammonites and especially brachiopods are more suitable tools for the Pliensbachian palaeobiogeographical reconstructions than bivalves.

New popcorn races in a diversity microcenter of Zea mays L. in the Far West of Santa Catarina, Southern Brazil

The last classification of corn races in Brazil was performed in 1977, when were described 19 races and 15 sub-races within four groups. However, this classification, which considered the race diversity in Brazil and South American lowlands, did not include popcorns. Therefore, there is a diversity in situ-on farm, which not yet was described after almost 40 years from the last study. This work aimed at identifying popcorn races from populations conserved in situ-on farm in the micro-region of the Far West of the State of Santa Catarina, Southern Brazil, and verifying their relationships with other races of the American continent. Thus, 218 ears of 70 popcorn populations were collected from small-scale farms, aiming to evaluate them for corn descriptors through 16 morphological characters related to ear and kernel. The populations showed variability for all characters, mainly for kernel color. The cluster analysis and principal coordinates, based on Gower index, have highlighted the presence of four distinct groups and one isolated population: I and II Groups, and the population 2279X are not grouped with other popcorn races of Americas, and Groups III and IV have different relationships with other popcorn races of Americas. Thus, in the region of study, there are at least five popcorn races conserved in situ-on farm.

Palaeobiogeographical affinity of the early Pliensbachian (Early Jurassic) brachiopod assemblage of the Northern Caucasus (Russia): A new evidence

Brachiopods are useful in detecting the Mesozoic palaeobiogeographical affinity of European terranes. Numerous representatives of this fossil group known from the lower Pliensbachian deposits of the Northern Caucasus (southwestern Russia) allow quantitative assessment of their palaeobiogeographical affinity. A total of 175 brachiopod species from the Northern Caucasus and several other regions (Bakony, Germany without the Alps, Hallstatt, the Pyrenees, Switzerland without the Southern Alps, the Swiss Southern Alps, and western Algeria) are considered for the purposes of the present study. The relationships between the regional assemblages were examined with three similarity indices, namely the Jaccard Index, the Czekanowski's Quantified Coefficient, and the Gower index. The results indicate the relatively strong similarity of the early Pliensbachian brachiopods of the Northern Caucasus to those of Germany, the Pyrenees, Switzerland, and western Algeria and the strong dissimilarity from the assemblages of the Bakony, Hallstatt, and the Swiss Southern Alps. These results reveal the affinity of the early Pliensbachian brachiopod assemblage of the Northern Caucasus to the Boreal biochore. However, there are Tethyan taxa in this assemblage, and, thus, the latter is of transitional nature. Palaeogeographical and plate tectonic configurations, eustatic fluctuations, differences between the regional depositional environments, etc. may explain the palaeobiogeographical patterns registered in the present study. The regional factors might have been especially important because of the moderate-to-weak global palaeobiogeographical differentiation in the early Pliensbachian. The concept of the Mediterranean microcontinent seems to be also useful for explanation of the early Pliensbachian brachiopod provinciality.

The hierarchical agglomerative clustering with Gower index: A methodology for automatic design of OLAP cube in ecological data processing context

The OLAP systems can be an improvement for ecological studies. In fact, ecology studies, follows and analyzes phenomenon across space and time and according to several parameters. OLAP systems can provide to ecologists browsing in a large dataset. One focus of the current research on OLAP system is the automatic design of OLAP cubes and of data warehouse schemas. This kind of works makes accessible OLAP technology to non information technology experts. But to be efficient, the automatic OLAP building must take into account various cases.Moreover the OLAP technology is based on the concept of hierarchy. Thereby the hierarchical clustering methods are often used by OLAP system designer.In this article, we propose using hierarchical agglomerative clustering with a metric that comes from ecological studies (the Gower similarity index) to build automatically hierarchical dimensions in an OLAP cube. With this similarity index we can perform a hierarchical clustering on heterogeneous datasets that contains qualitative and quantitative variables.We offer a prototypical automatic system which builds dimension for an OLAP cube and we measure the performances of this system according to the number of clustered individuals and according to the number of variables used for clustering. Thanks to these measures we can offer an approximation of performances with a large dataset.Thereby the Gower index in a hierarchical agglomerative clustering permits the management of heterogeneous dataset with missing values in a context of automatic building of OLAP cube. With this methodology, we can build new dimensions based on hierarchies in the data, which are not evident. The data mining methods can complete the expert knowledge during the design of an OLAP cube, because these methods can explain the inherent structure of the data.

Large-scale patterns in morphological diversity and species assemblages in Neotropical Triatominae (Heteroptera: Reduviidae)

We analysed the spatial variation in morphological diversity (MDiv) and species richness (SR) for 91 species of Neotropical Triatominae to determine the ecological relationships between SR and MDiv and to explore the roles that climate, productivity, environmental heterogeneity and the presence of biomes and rivers may play in the structuring of species assemblages. For each 110 km x 110 km-cell on a grid map of America, we determined the number of species (SR) and estimated the mean Gower index (MDiv) based on 12 morphological attributes. We performed bootstrapping analyses of species assemblages to identify whether those assemblages were more similar or dissimilar in their morphology than expected by chance. We applied a multi-model selection procedure and spatial explicit analyses to account for the association of diversity-environment relationships. MDiv and SR both showed a latitudinal gradient, although each peaked at different locations and were thus not strictly spatially congruent. SR decreased with temperature variability and MDiv increased with mean temperature, suggesting a predominant role for ambient energy in determining Triatominae diversity. Species that were more similar than expected by chance co-occurred near the limits of the Triatominae distribution in association with changes in environmental variables. Environmental filtering may underlie the structuring of species assemblages near their distributional limits.

Natural Experimentation Is a Challenging Method for Identifying Headache Triggers

In this study, we set out to determine whether individual headache sufferers can learn about the potency of their headache triggers (causes) using only natural experimentation. Headache patients naturally use the covariation of the presence-absence of triggers with headache attacks to assess the potency of triggers. The validity of this natural experimentation has never been investigated. A companion study has proposed 3 assumptions that are important for assigning causal status to triggers. This manuscript examines one of these assumptions, constancy in trigger presentation, using real-world conditions. The similarity of day-to-day weather conditions over 4 years, as well as the similarity of ovarian hormones and perceived stress over a median of 89 days in 9 regularly cycling headache sufferers, was examined using several available time series. An arbitrary threshold of 90% similarity using Gower's index identified similar days for comparison. The day-to-day variability in just these 3 headache triggers is substantial enough that finding 2 naturally similar days for which to contrast the effect of a fourth trigger (eg, drinking wine vs not drinking wine) will only infrequently occur. Fluctuations in weather patterns resulted in a median of 2.3 days each year that were similar (range 0-27.4). Considering fluctuations in stress patterns and ovarian hormones, only 1.5 days/month (95% confidence interval 1.2-2.9) and 2.0 days/month (95% confidence interval 1.9-2.2), respectively, met our threshold for similarity. Although assessing the personal causes of headache is an age-old endeavor, the great many candidate triggers exhibit variability that may prevent sound conclusions without assistance from formal experimentation or statistical balancing.

Measuring Autonomy Support in University Students: the Spanish Version of the Learning Climate Questionnaire

The goals of this research were to translate and analyze the psychometric properties of the Learning Climate Questionnaire (LCQ) and to develop a short form. The LCQ is a 15-item self-report measure that assesses autonomy support in educational settings. A total of 422 students (60 men and 362 women) took part in this study. Results showed evidence of construct validity and adequate reliability for the LCQ. The short form consists of five items that showed sound psychometric properties. Results of Pearson correlation and Gower index showed high agreement between the long and short forms. In conclusion, both forms can be considered as preliminary versions of the original questionnaire to assess autonomy support in educational settings.

Taxonomic diversity structure of Silurian crinoids: Stability versus dynamism

Taxonomic diversity structure of crinoids is measured as a number of genera in orders for each epoch of the Silurian. Changes in this structure are evaluated with two similarity indices, namely the Czekanowski's Quantified Coefficient and the Gower Index. Dynamics of the taxonomic diversity structure of crinoids was slow in the Silurian. The relatively strong turnovers occurred at the Ordovician – Silurian and Silurian – Devonian transitions. In contrast, the Wenlock – Ludlow transition was marked by an outstanding stability. When assemblages of non-successive epochs are considered, a persistence of similarity in this structure and a possibility of its re-appearance also indicate a certain stability. Nonetheless, some patterns of dynamism are also reported. The noted stability persisted despite palaeoenvironmental changes and biotic crises (like the end-Ordovician mass extinction and the Ireviken event). This highlights the role of intrinsic (biological) factors in the Silurian evolution of crinoids.

Evaluation of genetic dissimilarity in a segregating wine grape population

This study examined the genetic diversity present in a population obtained by crossing two very distinctive varieties of wine grapes (142 progeny from a Riesling x Cabernet Sauvignon cross, including both parents, created at the University of California). The following list of morphological characters were evaluated and found to segregate in this population: cluster weight, cluster length, presence or absence of cluster wings, cluster wing length, number of berries, cluster density (CD), and berry weight. The following juice parameters were also measured: °Brix, pH, total phenolics, and titratable acidity. Genetic diversity within this population was estimated through multivariate methods that utilized the Gower index of dissimilarity and UPGMA clustering. The correlations between traits and relative contribution of each variable were also compared. Eleven groups of progeny were distinguished into categories with low, intermediate and high values for cluster weight and cluster density, and low and high values for total phenolics. An inverse correlation was detected between the variables related to production and those related to the quality of the fruit. Principal components analysis demonstrated that all variables examined in this study are important for the correct discrimination of optimal genotypes in this population. These statistical tools can be used to select individuals with the greatest potential for producing high-quality wines.

Phanerozoic changes in the high-rank suprageneric diversity structure of brachiopods: Linear and non-linear effects

Phanerozoic evolution of brachiopods produced many linear (established by a comparison of successive geologic time units) and non-linear (established by a comparison of non-successive geologic time units) effects, which can be examined quantitatively by using the similarity coefficients (Czekanowski's Quantified Coefficient and Gower Index) and correlation tools. The high-rank suprageneric diversity structure accounts for a number of superfamilies in each of 26 orders for every epoch of geological time. The intensity of turnovers in this structure was generally low during the entire Phanerozoic. It was slightly stronger during the Early Paleozoic, but close to zero during the Cenozoic, when the high-rank suprageneric diversity structure of brachiopods stabilized finally. Significant turnovers took place at the Middle Cambrian–Early Ordovician, the Late Ordovician–Early Silurian, the Late Silurian–Early Devonian, the Middle Devonian–Mississippian, and the Permian–Triassic transitions. Influences of mass extinctions, both major like those End Ordovician or Permian/Triassic and minor like Early Jurassic or Jurassic/Cretaceous, on the high-rank suprageneric diversity structure of brachiopods is registered. The strongest was the consequences of the Permian/Triassic catastrophe, which perhaps even reset the brachiopod evolution. No evident direct relationships are established between intensity of turnovers and eustatic fluctuations. However, the changes in the diversity structure recorded with the Gower Index provide evidence that eustatic lowstands were more favorable for intensification in these changes.

Comparison of native and alien plant traits in Mediterranean coastal dunes

This study is part of a general project to analyse the biological and ecological mechanisms that influence the invasion of Mediterranean sand dune ecosystems by alien plants. In this paper we analyse the morphological and functional traits of coastal dune wild species (natives and aliens) based mainly on information from the literature. The most common 130 wild species occurring on the recent (Holocenic) coastal dunes were included considering the invasive status of alien plants. A comparative analysis of functional groups was performed through ordination techniques (PCoA using the Gower index). This reveals four functional groups related to the most important plant communities in coastal vegetation zonation. Alien plants were found in all functional groups and no trait or set of traits was specifically related to them. This indicates that aliens show similar traits to those natives growing in different communities of the coastal dune zonation, from the small beach annuals to the evergreen taller shrubs of the Mediterranean macchia. When the invasive status of alien species was taken into account, however, some differences emerged: a) casual aliens were found in almost all groups but their traits were not interpreted as being due to any particular adaptive strategy; b) naturalised aliens were only found in the less fluctuating habitats of the inner coastal zones; c) invasive alien species were connected with two major plant strategies: annual invasive aliens (quick-to-mature low grasses and herbs) and perennial invasive aliens (taller and often strongly clonal).

Multiple representations, similarity matching, and results fusion for content-based image retrieval

In this paper, we show how the use of multiple content representations and their fusion can improve the performance of content-based image retrieval systems. We consider the case of texture and propose a new algorithm for texture retrieval based on multiple representations and their results fusion. Texture content is modeled using two different models: the well-known autoregressive model and a perceptual model based on perceptual features such as coarseness and directionality. In the case of the perceptual model, two viewpoints are considered: perceptual features are computed based on the original images viewpoint and on the autocovariance function viewpoint (corresponding to original images). So we consider a total of three content representations. The similarity measure used is based on Gower's index of similarity. Simple results of the fusion models are used to merge search results returned by different representations. Experimentations and benchmarking carried out on the well-known Brodatz database show a drastic improvement in search effectiveness with the fused model without necessarily altering their efficiency in an important way.

A reliability index for presence-absence data

The Jaccard index has long been used as an indicator of agreement or similarity between two individuals regarding the presence or absence of attributes, but there has been no formal development of such an index for more than two individuals. A more general index would be useful in various kinds of reliability studies involving presence-absence data. This paper develops a special case of a generalization of Gower's index as an index of reliability. The index involves weights to be assigned to attributes which are present on varying proportions of the individuals. Possible weighting systems are discussed. Also, a theoretical basis for the index is investigated using a binomial distribution composited with a continuous attribute appearance probability distribution. The index is calculated for molecular biological data on repeated RAPD analyses of the DNA of 23 strains of a fungus.

A numerical study of the variation in the New Zealand erechtites arguta-scaberula complex (Senecioneae-Compositae)

Summary Thirteen numerical attributes taken from phyllaries, calycule, peduncle and florets were recorded for a sample of 65 specimens representing the New Zealand Erechtites arguta (syn. Senecio glomeratus)—Erechtites scaberula (syn. Senecio hispidulus) complex. The comparative data were subjected to computer analyses using Squared Euclidean Distance (D2 ) and Gower's Index as similarity statistics in conjunction with Nearest. Median and Furthest neighbour and Centroid (C) sorting strategies during the commissioning of ASSORT, a package of interrelated Algol procedures. The resulting agglomerative polythetic classifications conform to a basic structure exemplified by the D2 -C result. Two major groups consisting of four and five subgroups respectively were detected from the computed hierarchy. Thirteen additional characters taken from stem, leaf, involucre, corolla and achenes together with geographical data were used to show that the two major groups and only one subgroup exhibit taxonomic properties. R...