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    ABSTRACT: The analysis of beta diversity (inter-habitat diversity) of very species-rich and incompletely sampled tropical arthropod communities requires the choice of appropriate statistical tools. The performance of the three commonly employed ordination methods, correspondence analysis (CA), detrended correspondence analysis (DCA), and nonmetric multidimensional scaling (NMDS), was compared on a large empirical data set of geometrid moths sampled along an altitudinal gradient in an Andeanmontane rain forest. Despite the high species richness and incompleteness of the ensembles, allmethods depicted the same, readily interpretable patterns. BothCAandNMDSshowed an arch-like structure, which hints at an underlying coenocline, whereas this arch was computationally eliminated in DCA. For this particular data set, CA and NMDS both provided convincing results while the detrending algorithm of DCA did not improve the interpretability of the data. Of the large number of similarity indices available to be used in combination with NMDS, the binary Sørensen and the abundance-based Normalized Expected Species Shared (NESS) index were tested. Performance of the indices was measured by comparing stress, a measure of poorness-of-fit in NMDS. NMDS ordinations with lowest values of stress were achieved by the NESS index with the parameter m set to its maximum (mmax). In contrast, ordinations based on NESS values with the parameter m set to 1 (identical with Morisita’s index), had consistently higher stress values and performed worse than ordinations using Sørensen’s index. Hence, if high values of m can be achieved in similar data sets, the NESS index with mmax is recommended for ordination purposes and Morisita’s index should be avoided.
    Journal of Tropical Ecology 01/2004; 20:165-172. · 1.48 Impact Factor
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    ABSTRACT: Hebert and colleagues (2004) used a short region of the mitochondrial Cytochrome oxidase subunit I gene as a delimiter for ten putative species from among 466 individuals of the skipper butterfly currently known as Astraptes fulgerator from Guanacaste, Costa Rica. Their data are reanalysed to assess cluster stability and clade support using Neighbor‐Joining bootstrap, population aggregation analysis and cladistic haplotype analysis. At least three, but not more than seven mtDNA clades that may correspond to cryptic species are supported by the evidence. Additional difficulties with Hebert et al.’s interpretation of the data are discussed.
    Systematics and Biodiversity 01/2006; 4:127-132. · 1.88 Impact Factor
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    ABSTRACT: Andean montane rain forests are among the most species-rich terrestrial habitats. Little is known about their insect communities and how these respond to anthropogenic habitat alteration. We investigated exceptionally speciose ensembles of nocturnal tiger moths (Arctiidae) at 15 anthropogenically disturbed sites, which together depict a gradient of forest recovery and six closed-forest understorey sites in southern Ecuador. At weak light traps we sampled 9211 arctiids, representing 287 species. Arctiid abundance and diversity were highest at advanced succession sites, where secondary scrub or young forest had re-established, followed by early succession sites, and were lowest, but still high, in mature forest understorey. The proportion of rare species showed the reverse pattern. We ordinated moth samples by non-metric multidimensional scaling using the chord-normalized expected species shared index (CNESS) index at various levels of the sample size parameter m. A distinct segregation of arctiid ensembles at succession sites from those in mature forest consistently emerged only at high m-values. Segregation between ensembles of early vs. late succession stages was also clear at high m values only, and was rather weak. Rare species were responsible for much of the faunal difference along the succession gradient, whereas many common arctiid species occurred in all sites. Matrix correlation tests as well as exploration of relationships between ordination axes and environmental variables revealed the degree of habitat openness, and to a lesser extent, elevation, as best predictors of faunal dissimilarity. Faunal differences were not related to geographical distances between sampling sites. Our results suggest that many of the more common tiger moths of Neotropical montane forests have a substantial recolonization potential at the small spatial scale of our study and accordingly occur also in landscape mosaics surrounding nature reserves. These species contribute to the unexpectedly high diversity of arctiid ensembles at disturbed sites, whereas the proportion of rare species declines outside mature forest.
    Diversity and Distributions 06/2005; 11(5):387 - 398. · 6.12 Impact Factor

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