1,721,009 research outputs found
RPB2 gene reveals a phylodemographic signal in wild and domesticated grapevine (Vitis vinifera)
No full textUntangling the Evolution of American Wild Grapes: Admixed Species and How to Find Them
No full textNatural hybridization and introgression are central evolutionary processes in grape genus (Vitis). On the other hand, the interspecific relationships among grapes, the directionality of the inferred admixture events and the parents of hybrids are not yet completely clarified. The grapes are economically important crops characterized by tendrils used to climb on the trees and the fruits harvested by humans especially for the consumption or to produce wines and liquors. The American grapes (ca. 30 species) are recognized as an important resource because they show biotic and abiotic resistances. We analyzed 3,885 genome-wide SNPs from 31 American Vitis species using the TreeMix software combined with the f3 and f4 tests. This approach allowed us to infer phylogenetic relationships and to explore the natural admixture among taxa. Our results confirmed the existence of all hybrid species recognized in literature (V. x champinii, V. x doaniana, V. x novae-angliae, and V. x slavinii), identifying their most likely parent species and provided evidence of additional gene flows between distantly related species. We discuss our results to elucidate the origin of American wild grapes, demonstrating that admixture events have ancient origins. We observe that gene flows have involved taxa currently spread through the southern regions of North America. Consequently, we propose that glacial cycles could have triggered the contact between interfertile taxa promoting local hybridization events. We conclude by discussing the phylogenetic implications of our findings and showing that TreeMix can provide novel insights into the evolutionary history of grapes
Multiple evolutionary lineages detected in giant reed (Arundo donax L.): Applied and evolutionary perspectives
No full textIdentification of independent evolutionary lineages is a modern challenge for biologists especially in crops with high potential. Molecular methods, usually used to explore intraspecific variation, also offer important information regarding how and when lineages have evolved and spread. Today, several tools to define the demarcation of lineages based on single or multi-locus data are available, permitting objective results to be obtained. We tested nuclear and plastid loci using five different approaches to delimit the major lineages and estimate the divergence times in giant reed (Arundo donax L.). It is an emerging energy crop, widespread in sub-tropical and temperate regions but particularly aggressive outside its native range. Our results support the presence of six lineages distributed from the Asian regions to the Mediterranean basin and indicate the western and southern edges of the Qinghai-Tibet Plateau as the putative area of origin and source of ancient and cryptic lineages. We suppose it could be an area that has fertile populations. These results should be considered in breeding programmes to produce new cultivars, especially because the absence of fertility for Mediterranean giant reed lineages reduces the opportunity of crop improvement. Moreover, the description of multiple lineages and identifying its putative ancestral area may be helpful to researchers working on invasiveness management, phytoremediation programmes and conservation biology
Regularity results for local solutions to some anisotropic elliptic equations
No full textIn this paper we study the higher integrability of local solutions for a class of anisotropic equations with lower order terms whose growth coefficients lay in Marcinkiewicz spaces. A condition for the boundedness of such solutions is also given
Allopatric divergence and secondary contacts in Euphorbia spinosa L: Influence of climatic changes on the split of the species
No full textEuphorbia spinosa, a perennial xerophilous shrub
naturally distributed across the Italian peninsula, was selected
for examination of the role of the Ligurian Alps and
Apennines in glacial survival. The Italian Peninsula is
considered to be one of the principal glacial refugia in
Europe, but few plant population genetic and phylogeography
studies have been undertaken in this region. The
combined analysis of chloroplast and nuclear loci (ITS,
cpSSR and ISSR) enabled us to detect extensive DNA
variation and proved to be a very powerful tool for the
reconstruction of the phylogeography. Molecular data support
the hypothesis of a long-term separation of the Northwestern
(Maritime Alps, Sardinia, Corsica, Northern Apennines) and
Southeastern (Southern Apennines and Balkan area) lineages
in glacial refugia. The existence of allopatrically fragmented
lineages is most probably the result of isolation in different
glacial refugia, possibly due to the Last Glacial Maximum
cooling and the topographic complexity of the Italian
peninsula. The most plausible hypothesis assumes the
formation of two migration paths during more recent periods:
the first one starting with southward migration and the
second one moving northwards. The Central Apennines
should be considered the confluence of migration routes
radiating from separate refugia according to this hypothesis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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