1,721,170 research outputs found
Untangling 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
L’ABC delle Biotecnologie
No full textl'articolo propone una rassegna dei pro e contro dell'utilizzo delle biotecnologie applicate al campo agrario e delle innovazioni tecnologiche e scientifiche che si stanno realizzando in questo settore
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
Haplotype richness in refugial areas: phylogeographical structure of Saxifraga callosa
No full textThis paper illustrates the phylogeographical
structure of Saxifraga callosa in order to describe its
genetic richness in refugial areas and to reconstruct its
glacial history. S. callosa is a species spread throughout
south-east France and Italy with a high distribution in the
Maritime Alps. Four chloroplast microsatellite and AFLP
markers were analyzed in populations of S. callosa. The
size variants of all tested loci amount to 11 different haplotypes.
Intrapopulational haplotype variation was found in
two of the populations analyzed: on the Mt. Toraggio in the
Maritime Alps, and in the Apuan Alps. On the other hand,
no intrapopulational variation was found in 25 populations,
most of which were sampled from isolated areas. Analysis
of the haplotype distribution showed that population subdivision
across all populations was high (GST = 0.899).
Moreover, its genetic structure was studied using AMOVA
and STRUCTURE analysis. The study legitimated inferred
conclusions about the phylogeographical structure of the
species and identified centers of diversity. Considerations
concerning genetic structure and divergence among three
major clades (Maritime Alps, Apuan Alps and Apennines),
the patchy distribution of haplotypes, and the high number
of private haplotypes support the proposal that S. callosa
survived in some refugia within the Italian Peninsula
refugium, and that mainly northern populations of refugia
were involved in postglacial recolonization
Natural hybridization in Saxifraga callosa Sm.
No full textSaxifraga callosa Sm. is an evergreen perennial species
distributed from Eastern Spain, through the Western Alps and
the Apennines, to southern Italy. The existence of high morphological
variation within different subspecies indicates that phenotypic
characters are useful but not sufficient taxonomic tools.
Indeed, available morphological data already suggested that S.
callosa subentity lantoscana may be an outcross between S. callosa
and S. cochlearis. In this work, by analyzing ITS (Internal
Transcribed Sequences), AFLP (Amplified Fragment Length Polymorphisms),
and cpDNA (chloroplast DNA) markers, a comprehensive
study of the genomic relationships among S. callosa
and related species has been carried out. The sequence of the
ITS region of S. callosa subentity lantoscana gave no conclusive
results on the taxonomy status of S. callosa subentity lantoscana.
On the other hand, the use of the “NewHybrids” software to analyze
an AFLP data-set (208 polymorphic amplified fragments)
supported a significant posterior probability that S. callosa subentity
lantoscana individuals are natural hybrids between S. callosa
and S. cochlearis. The level of introgression of genes from
alien genomes was confirmed by a simpler and quick methodology
that analyze length variation in cpDNA sequences
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
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