1,461 research outputs found
Mit kleinen Schnipseln zum großen Stammbaum
No full textZusammenfassung Die Beziehungen der europäischen Strauchweiden (Gattung Salix, Untergattungen Chamaetia und Vetrix) waren bislang völlig unklar. Im Gegensatzu zu bisherigen molekularen Methoden, die zu wenig Informationen lieferten, konnten mithilfe des modernen DNA‐Sequenzierverfahrens, dem R estriction site A ssociated D NA seq uencing (RAD sequencing), tausende informative Positionen des Genoms detektiert werden. Auf Basis dieser Daten konnte erstmals herausgefunden werden, dass die einzelnen beschriebenen Arten gut unterstützt werden, aber der traditionellen taxonomischen Eingruppierung aller Zwergweiden in eine gemeinsame Untergattung mithilfe der molekularen Daten klar widersprochen wird. Zwergsträucher sind offensichtlich als Anpassung an arktisch‐alpine Lebensräume mehrfach unabhängig voneinander entstanden.Summary The relationships and speciation processes in European shrub willows (Salix subg. Chamaetia and Vetrix) is still poorly understood. This group consists of small, few centimetre high dwarf shrubs as well as of big trees. The questions that arise are i) How are the relationships within these two subgenera? ii) Do molecular markers confirm the traditional taxonomic treatment? iii) Which adaptations evolved on arctic‐alpine habitats? Based on r estriction site a ssociated D NA seq uencing (RAD sequencing), a recent method that generates thousands of informative sites, these questions could be addressed for the very first time. The molecular data revealed that dwarf shrubs evolved several times independently and do therewith not confirm the traditional taxonomical classification
The Evolutionary History, Diversity, and Ecology of Willows (Salix L.) in the European Alps
No full textThe genus Salix (willows), with 33 species, represents the most diverse genus of woody plants in the European Alps. Many species dominate subalpine and alpine types of vegetation. Despite a long history of research on willows, the evolutionary and ecological factors for this species richness are poorly known. Here we will review recent progress in research on phylogenetic relationships, evolution, ecology, and speciation in alpine willows. Phylogenomic reconstructions suggest multiple colonization of the Alps, probably from the late Miocene onward, and reject hypotheses of a single radiation. Relatives occur in the Arctic and in temperate Eurasia. Most species are widespread in the European mountain systems or in the European lowlands. Within the Alps, species differ ecologically according to different elevational zones and habitat preferences. Homoploid hybridization is a frequent process in willows and happens mostly after climatic fluctuations and secondary contact. Breakdown of the ecological crossing barriers of species is followed by introgressive hybridization. Polyploidy is an important speciation mechanism, as 40% of species are polyploid, including the four endemic species of the Alps. Phylogenomic data suggest an allopolyploid origin for all taxa analyzed so far. Further studies are needed to specifically analyze biogeographical history, character evolution, and genome evolution of polyploids
Rapid loss of plastid ndh genes in slipper orchids (Cypripedioideae, Orchidaceae)
Full text linkOpen-Access-Publikationsfonds 202
Highly Diverse Shrub Willows (Salix L.) Share Highly Similar Plastomes
Full text linkPlastome phylogenomics is used in a broad range of studies where single markers do not bear enough information. Phylogenetic reconstruction in the genus Salix is difficult due to the lack of informative characters and reticulate evolution. Here, we use a genome skimming approach to reconstruct 41 complete plastomes of 32 Eurasian and North American Salix species representing different lineages, different ploidy levels, and separate geographic regions. We combined our plastomes with published data from Genbank to build a comprehensive phylogeny of 61 samples (50 species) using RAxML (Randomized Axelerated Maximum Likelihood). Additionally, haplotype networks for two observed subclades were calculated, and 72 genes were tested to be under selection. The results revealed a highly conserved structure of the observed plastomes. Within the genus, we observed a variation of 1.68%, most of which separated subg. Salix from the subgeneric Chamaetia/Vetrix clade. Our data generally confirm previous plastid phylogenies, however, within Chamaetia/Vetrix phylogenetic results represented neither taxonomical classifications nor geographical regions. Non-coding DNA regions were responsible for most of the observed variation within subclades and 5.6% of the analyzed genes showed signals of diversifying selection. A comparison of nuclear restriction site associated DNA (RAD) sequencing and plastome data on a subset of 10 species showed discrepancies in topology and resolution. We assume that a combination of (i) a very low mutation rate due to efficient mechanisms preventing mutagenesis, (ii) reticulate evolution, including ancient and ongoing hybridization, and (iii) homoplasy has shaped plastome evolution in willows
Data from: RAD-seq reveals genetic structure of the F2-generation of natural willow hybrids (Salix L.) and a great potential for interspecific introgression
No full textBackground: Hybridization of species with porous genomes can eventually lead to introgression via repeated backcrossing. The potential for introgression between species is reflected by the extent of segregation distortion in later generation hybrids. Here we studied a population of hybrids between Salix purpurea and S. helvetica that has emerged within the last 30 years on a glacier forefield in the European Alps due to secondary contact of the parental species. We used 5,758 biallelic SNPs produced by RAD sequencing with the aim to ascertain the predominance of backcrosses (F1 hybrid x parent) or F2 hybrids (F1 hybrid x F1 hybrid) among hybrid offspring. Further, the SNPs were used to study segregation distortion in the second hybrid generation. Results: The analyses in STRUCTURE and NewHybrids revealed that the population consisted of parents and F1 hybrids, whereas hybrid offspring consisted mainly of backcrosses to either parental species, but also some F2 hybrids. Although there was a clear genetic differentiation between S. purpurea and S. helvetica (FST = 0.24), there was no significant segregation distortion in the backcrosses or the F2 hybrids. Plant height of the backcrosses resembled the respective parental species, whereas F2 hybrids were more similar to the subalpine S. helvetica.
Conclusions: The co-occurrence of the parental species and the hybrids on the glacier forefield, the high frequency of backcrossing, and the low resistance to gene flow via backcrossing make a scenario of introgression in this young hybrid population highly likely, potentially leading to the transfer of adaptive traits. We further suggest that this willow hybrid population may serve as a model for the evolutionary processes initiated by recent global warming
Phylogenomic Relationships and Evolution of Polyploid Salix Species Revealed by RAD Sequencing Data
No full textPolyploidy is common in the genus Salix. However, little is known about the origin, parentage and genomic composition of polyploid species because of a lack of suitable molecular markers and analysis tools. We established a phylogenomic framework including species of all described sections of Eurasian shrub willows. We analyzed the genomic composition of seven polyploid willow species in comparison to putative diploid parental species to draw conclusions on their origin and the effects of backcrossing and post-origin evolution. We applied recently developed programs like SNAPP, HyDe, and SNiPloid to establish a bioinformatic pipeline for unravelling the complexity of polyploid genomes. RAD sequencing revealed 23,393 loci and 320,010 high quality SNPs for the analysis of relationships of 35 species of Eurasian shrub willows (Salix subg. Chamaetia/Vetrix). Polyploid willow species appear to be predominantly of allopolyploid origin. More ancient allopolyploidization events were observed for two hexaploid and one octoploid species, while our data suggested a more recent allopolyploid origin for the included tetraploids and identified putative parental taxa. SNiPloid analyses disentangled the different genomic signatures resulting from hybrid origin, backcrossing, and secondary post-origin evolution in the polyploid species. Our RAD sequencing data demonstrate that willow genomes are shaped by ancient and recent reticulate evolution, polyploidization, and post-origin divergence of species
Insights into the Taxonomically Challenging Hexaploid Alpine Shrub Willows of Salix Sections Phylicifoliae and Nigricantes (Salicaceae)
No full textThe complex genomic composition of allopolyploid plants leads to morphologically diverse species. The traditional taxonomical treatment of the medium-sized, hexaploid shrub willows distributed in the Alps is difficult based on their variable morphological characters. In this study, RAD sequencing data, infrared-spectroscopy, and morphometric data are used to analyze the phylogenetic relationships of the hexaploid species of the sections Nigricantes and Phylicifoliae in a phylogenetic framework of 45 Eurasian Salix species. Both sections comprise local endemics as well as widespread species. Based on the molecular data, the described morphological species appeared as monophyletic lineages (except for S. phylicifolia s.str. and S. bicolor, which are intermingled). Both sections Phylicifoliae and Nigricantes are polyphyletic. Infrared-spectroscopy mostly confirmed the differentiation of hexaploid alpine species. The morphometric data confirmed the molecular results and supported the inclusion of S. bicolor into S. phylicifolia s.l., whereas the alpine endemic S. hegetschweileri is distinct and closely related to species of the section Nigricantes. The genomic structure and co-ancestry analyses of the hexaploid species revealed a geographical pattern for widespread S. myrsinifolia, separating the Scandinavian from the alpine populations. The newly described S. kaptarae is tetraploid and is grouped within S. cinerea. Our data reveal that both sections Phylicifoliae and Nigricantes need to be redefined
Niche expansion of polyploid cytotypes shaped the phylogeographical history of the Salix retusa complex in the European Alpine System
No full textAbstract Background and Aims Alpine plants exhibit diverse postglacial recolonization patterns following the last glacial periods. Polyploidization may have impacted these dynamics by introducing ecological and physiological novelties that facilitate adaptation to changing environments. However, consistent trends in the recolonization, niche optima and dynamics of polyploids and their related diploids remain elusive. In this study, we investigate the biogeographical history of the Salix retusa polyploid complex in the European Alpine System. By comparing genetic patterns and their climatic and edaphic niche optima, we explore how polyploidization shaped species’ geographical distributions by influencing their ecological adaptation. Methods RAD sequencing was used to reconstruct the biogeographical history and genetic structure of two related willow species. High-resolution edaphic and climatic data were used to compare the niche optima, breadth and dynamics between the species. Key Results The distribution of the polyploid species overlaps with more peripheral refugial areas, which correlates with its broader geographical range in the European Alpine System. However, genetic analyses suggest more potential peripheral glacial refugia within the Alps for the diploid. Our findings indicate niche conservatism within the S. retusa complex, with the polyploid species having a broader niche but the diploid being adapted to a more extreme niche. Conclusions In our study species, polyploidy is associated with a higher genetic diversity and geographical structure, which might be due to a broader ecological niche and distribution. However, it did not appear to facilitate adaptation or confer a survival advantage during the last glaciation
Hybrid zones in the European Alps impact the phylogeography of alpine vicariant willow species (Salix L.)
Full text linkIn the European Alps, Pleistocene climate oscillations resulted in geographical range expansions and restrictions of species. Postglacial recolonizations often result in secondary contact hybridization of vicariant species, thereby creating hybrid zones with patterns of introgression. Here, we compare the genetic structure of two secondary contact hybrid zones between two vicariant willow species pairs occurring in the European Alpine System. Supplemented by morphological and ecological data, we try to understand the factors shaping the hybrid zones and their influence on geographical range filling patterns.Open-Access-Publikationsfonds 202
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