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Agglomerative Clustering (agglomerative + clustering)
Selected AbstractsComparing agglomerative clustering and three weed classification frameworks to assess the invasiveness of alien species across spatial scalesDIVERSITY AND DISTRIBUTIONS, Issue 6 2006Roger A. Lawes ABSTRACT To prioritize weed management at the catchment scale, information is required on the species present, their relatively frequency, abundance, and likely spread and impact. The objective of this study was to classify the invasiveness of alien species that have invaded the Upper Burdekin Catchment in Queensland, Australia, at three spatial scales. A combination of three published weed classification frameworks and multivariate techniques were employed to classify species based on their frequency and cover at a range of spatial scales. We surveyed the Upper Burdekin Catchment for alien species, and for each species determined the following distribution indices , site frequency, total cover, transect frequency per site frequency and quadrat frequency per site frequency, cover per quadrat when present, cover per transect when present, and cover per site when present. These indices capture the effect of species abundance and frequency between sites (site frequency and total cover), within sites (transect frequency per site and cover per transect when present), and within transects (quadrat frequency per site frequency and cover per site). They were used to classify the species into seven groups using a hierarchical cluster analysis. The relationship between the indices was explored to determine how effective the small scale, site-specific indices were at predicting the broader, landscape-scale patterns. Strong correlations were observed between transect frequency per site and frequency (r2 = 0.89) and cover per transect when present and total cover (r2 = 0.62). This suggests that if a weed is abundant at the site level, it has the potential to occupy large areas of the catchment. The species groupings derived from the application of the three published weed classification frameworks were compared graphically to the groupings derived from the cluster analysis. One of the frameworks classified species into three groups. The other two frameworks classified species into four groups. There was a high degree of subjectivity in applying the frameworks to the survey data. Some of the data were of no relevance to the classification frameworks and were therefore ignored. We suggest that the weed classification frameworks should be used in conjunction with existing multivariate techniques to ensure that classifications capture important natural variations in observed data that may reflect invasion processes. The combined use of the frameworks and multivariate techniques enabled us to aggregate species into categories appropriate for management. [source] A study on interaspecific biodiversity of eight groups of silkworm (Bombyx mori) by biochemical markersINSECT SCIENCE, Issue 2 2005KAYVAN ETEBARI Abstract The recognition of biodiversity in different races and lines of silkworm (Bombyx mori) is very useful for breeding programs and production of high efficiency hybrids. In this study eight groups of silkworm were selected including 103, 107, Xihang 1 and 2 of Japanese origin and 104, 110, Koming 1 and 2 of Chinese origin. The activity levels of three enzymes including alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase in haemolymph of fifth instar larva were measured. Moreover, the quantitative amount of total protein, cholesterol and glucose of haemolymph was evaluated. The data reveal that the activity level of measured macromolecules except for alkaline phosphatase were significantly different in all the groups. Hierarchical agglomerative clustering under UPGMA model separated line 104 from other groups. Two groups of Koming 1 and Xihang 1 had the most intergroup similarities. [source] Large-scale spatio-temporal shifts in the diet of a predator mediated by an emerging infectious disease of its main preyJOURNAL OF BIOGEOGRAPHY, Issue 8 2009Marcos Moleón Abstract Aim, To explore the influence of an emerging infectious disease (EID) affecting a prey species on the spatial patterns and temporal shifts in the diet of a predator over a large geographical scale. We reviewed studies on the diet of Bonelli's eagles (Hieraaetus fasciatus) in order to determine the repercussions of the reduction in the density of its main prey, the rabbit (Oryctolagus cuniculus), caused by outbreaks of rabbit haemorrhagic disease (RHD) since 1988. Location, Western continental Europe. Methods, We compiled published and unpublished information on the diet of breeding Bonelli's eagles from Portugal, Spain and France for a 39-year study period (1968,2006). Nonparametric tests were used in order to analyse temporal shifts in diet composition and trophic diversity (H,) between the periods of ,high' (before outbreak of RHD) and ,low' rabbit density (after outbreak of RHD). A combination of hierarchical agglomerative clustering and non-metric multidimensional scaling (NMDS) analyses were used to test for the existence of geographical patterns in the diet of Bonelli's eagles in each period. Results, The diet of the Bonelli's eagle consisted of rabbit (28.5%), pigeons (24.0%), partridges (15.3%), ,other birds' (11.6%), ,other mammals' (7.1%), corvids (7.0%), and herptiles (6.4%). However, RHD had large consequences for its feeding ecology: the consumption of rabbits decreased by one-third after the outbreak of RHD. Conversely, trophic diversity (H,) increased after outbreak of RHD. At the same time, the analyses showed clear geographical patterns in the diet of the Bonelli's eagle before, but not after, RHD outbreak. Main conclusions, Geographical patterns in the diet of the Bonelli's eagle in western Europe seem to be driven mainly by spatio-temporal variation in the abundance of rabbits and, to a lesser extent, by the local (territorial) environmental features conditioning the presence and density of alternative prey species. We show that an EID can disrupt predator,prey relationships at large spatial and temporal scales through a severe decline in the population of the main prey species. Hence we argue that strict guidelines should be drawn up to prevent human-aided dissemination of ,pathogen pollution', which can threaten wildlife not only at the population and species level but also at the community and ecosystem scale. [source] SMIXTURE: strategy for mixture model clustering of multivariate imagesJOURNAL OF CHEMOMETRICS, Issue 11-12 2005Thanh N. Tran Abstract SMIXTURE, a novel strategy for mixture model clustering of multivariate images, has been developed. Most other clustering approaches require good guesses of the number of components (clusters) and the initial statistical parameters. In our approach, the initial parameters are determined by agglomerative clustering on homogenous regions, identified by region growing segmentation. SMIXTURE can be used in both a normal situation of mixture modeling, where the density of a cluster is modeled by a single normal distribution; and in a more complex situation, where the density of a single cluster is a mixture of several normal sub-clusters. The method has proven to be very robust to noise/outliers, overlapping clusters, is reasonably fast and is suitable for moderate to large images. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||