687 research outputs found

    Review of \u3cem\u3eWhen the Devil Knocks: The Congo Tradition and the Politics of Blackness in Twentieth-Century Panama\u3c/em\u3e

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    Roll 91. New York - SLU at St. John's. Image 3 of 20. (28 December, 1953) [PHO 1.91.3]The Boleslaus Lukaszewski (Father Luke) Photographs contain more than 28,000 images of Saint Louis Univrsity people, activities, and events between 1951 and 1970. The photographs were taken by Boleslaus Lukaszewski (Father Luke), a Jesuit priest and member of the University's Philosophy Department faculty

    Barcoding success as a function of phylogenetic relatedness in Viburnum, a clade of woody angiosperms

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    BACKGROUND: The chloroplast genes matK and rbcL have been proposed as a “core” DNA barcode for identifying plant species. Published estimates of successful species identification using these loci (70-80%) may be inflated because they may have involved comparisons among distantly related species within target genera. To assess the ability of the proposed two-locus barcode to discriminate closely related species, we carried out a hierarchically structured set of comparisons within Viburnum, a clade of woody angiosperms containing ca. 170 species (some 70 of which are currently used in horticulture). For 112 Viburnum species, we evaluated rbcL + matK, as well as the chloroplast regions rpl32-trnL, trnH-psbA, trnK, and the nuclear ribosomal internal transcribed spacer region (nrITS). RESULTS: At most, rbcL + matK could discriminate 53% of all Viburnum species, with only 18% of the comparisons having genetic distances >1%. When comparisons were progressively restricted to species within major Viburnum subclades, there was a significant decrease in both the discriminatory power and the genetic distances. trnH-psbA and nrITS show much higher levels of variation and potential discriminatory power, and their use in plant barcoding should be reconsidered. As barcoding has often been used to discriminate species within local areas, we also compared Viburnum species within two regions, Japan and Mexico and Central America. Greater success in discriminating among the Japanese species reflects the deeper evolutionary history of Viburnum in that area, as compared to the recent radiation of a single clade into the mountains of Latin America. CONCLUSIONS: We found very low levels of discrimination among closely related species of Viburnum, and low levels of variation in the proposed barcoding loci may limit success within other clades of long-lived woody plants. Inclusion of the supplementary barcodes trnH-psbA and nrITS increased discrimination rates but were often more effective alone rather than in combination with rbcL + matK. We surmise that the efficacy of barcoding in plants has often been overestimated because of the lack of comparisons among closely related species. Phylogenetic information must be incorporated to properly evaluate relatedness in assessing the utility of barcoding loci

    Phylogeny and biogeography of Morinaceae (Dipsacales) based on nuclear and chloroplast DNA sequences

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    AbstractThe Morinaceae (Dipsacales) contains 13 species placed in Acanthocalyx, Cryptothladia or Morina, and is distributed from the mountains of southeastern Europe through the Himalayas to the Qinghai-Tibetan Plateau, mainly in alpine habitats. Sequence data from two chloroplast regions (the trnK intron and the trnL-F region) and the internal transcribed spacer (ITS) region of nuclear ribosomal DNA were used to infer phylogenetic relationships of Morinaceae and related Dipsacales. Both the nuclear and chloroplast datasets, as well as the combined data, provide strong support for relationships within the Valerina clade, placing Morinaceae as the sister group of a clade containing Valerianaceae and Dipsacaceae plus Triplostegia. The Morinaceae, Acanthocalyx, Cryptothladia, and a clade containing Morina and Cryptothladia, are all supported as monophyletic. However, Morina was found to be paraphyletic in several of our analyses, with Morina longifolia more closely related to Cryptothladia than to other Morina species. There is some evidence that Morina longifolia produces cleistogamous flowers, as do Cryptothladia species. Dispersal-vicariance analyses support the view that Valerina radiated initially within Asia, with subsequent movement into Europe in Morinaceae, Dipsacaceae, and Valerianaceae, and into the New World in Valerianaceae. For Morinaceae, as for a number of plant groups, the Brahmaputra river drainage marks a significant biogeographic divide, although this has been spanned within Acanthocalyx and the Morina-Cryptothladia lineage

    A New Technique for Measuring the Strangemess Content of the Proton on the Lattice

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    A new technique for computing the strangeness content of the proton on the lattice is described. It is applied to the calculation of the strange quark contribution to the proton's spin, specifically to the evaluation of the proton matrix element of the strange quark axial current. Preliminary results are not in disagreement with the EMC experiment. NOTE: This paper is available only in postscript form.Comment: 8 pages, figures included in the text, all in postscrip

    A Southern Hemisphere origin for campanulid angiosperms, with traces of the break-up of Gondwana

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    Background New powerful biogeographic methods have focused attention on long-standing hypotheses regarding the influence of the break-up of Gondwana on the biogeography of Southern Hemisphere plant groups. Studies to date have often concluded that these groups are too young to have been influenced by these ancient continental movements. Here we examine a much larger and older angiosperm clade, the Campanulidae, and infer its biogeographic history by combining Bayesian divergence time information with a likelihood-based biogeographic model focused on the Gondwanan landmasses. Results Our analyses imply that campanulids likely originated in the middle Albian (~105 Ma), and that a substantial portion of the early evolutionary history of campanulids took place in the Southern Hemisphere, despite their greater species richness in the Northern Hemisphere today. We also discovered several disjunctions that show biogeographic and temporal correspondence with the break-up of Gondwana. Conclusions While it is possible to discern traces of the break-up of Gondwana in clades that are old enough, it will generally be difficult to be confident in continental movement as the prime cause of geographic disjunctions. This follows from the need for the geographic disjunction, the inferred biogeographic scenario, and the dating of the lineage splitting events to be consistent with the causal hypothesis

    Mega-phylogeny approach for comparative biology: an alternative to supertree and supermatrix approaches

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    Abstract Background Biology has increasingly recognized the necessity to build and utilize larger phylogenies to address broad evolutionary questions. Large phylogenies have facilitated the discovery of differential rates of molecular evolution between trees and herbs. They have helped us understand the diversification patterns of mammals as well as the patterns of seed evolution. In addition to these broad evolutionary questions there is increasing awareness of the importance of large phylogenies for addressing conservation issues such as biodiversity hotspots and response to global change. Two major classes of methods have been employed to accomplish the large tree-building task: supertrees and supermatrices. Although these methods are continually being developed, they have yet to be made fully accessible to comparative biologists making extremely large trees rare. Results Here we describe and demonstrate a modified supermatrix method termed mega-phylogeny that uses databased sequences as well as taxonomic hierarchies to make extremely large trees with denser matrices than supermatrices. The two major challenges facing large-scale supermatrix phylogenetics are assembling large data matrices from databases and reconstructing trees from those datasets. The mega-phylogeny approach addresses the former as the latter is accomplished by employing recently developed methods that have greatly reduced the run time of large phylogeny construction. We present an algorithm that requires relatively little human intervention. The implemented algorithm is demonstrated with a dataset and phylogeny for Asterales (within Campanulidae) containing 4954 species and 12,033 sites and an rbcL matrix for green plants (Viridiplantae) with 13,533 species and 1,401 sites. Conclusion By examining much larger phylogenies, patterns emerge that were otherwise unseen. The phylogeny of Viridiplantae successfully reconstructs major relationships of vascular plants that previously required many more genes. These demonstrations underscore the importance of using large phylogenies to uncover important evolutionary patterns and we present a fast and simple method for constructing these phylogenies.</p
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