1,721,074 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
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
Misfortunes never come singly: Structural change, multiple shocks and child malnutrition in rural Senegal
Full text linkThis study considers the two most pronounced shocks Senegalese subsistence farmers struggle with, namely increasing purchase prices and droughts. We assess the relationship of these self-reported shocks with child health in a multi-shock approach to account for concomitance of adverse events from the natural, biological, economic and health sphere. We employ a unique farming household panel dataset containing information on children living in poor, rural households in eight regions of Senegal in 2009 and 2011 and account for structural changes occurring between survey periods due to the large scale, national Nutrition Enhancement Program. By zooming in to the micro level we demonstrate that Senegal as a Sahelian country, mainly reliant on subsistence agriculture, is very vulnerable to climate variability and international price developments: According to our conservative estimates, the occurrence of a drought explains 25% of the pooled weight-for-age standard deviation, income losses 31%. Our multi-shock analysis reveals that the shocks are perceived as more severe in 2011 with droughts explaining up to 44% of the standard deviation of child health, increased prices up to 21%. Yet, the concomitance of droughts and increased prices after the structural change, i.e. the Nutrition Enhancement Program, indicates that the health of children experiencing both shocks in 2011 has improved. We argue that these results are driven by the increase in rural household income as theoretically outlined in the agricultural household model. Thus, adequate policy responses to shocks do not only depend on the nature but also on the concomitance of hazardous events
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
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
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
Conservation in the face of hybridisation: genome-wide study to evaluate taxonomic delimitation and conservation status of a threatened orchid species
No full textThis study assessed inter- and intraspecific relationships and genetic structure in an Australian species complex in the helmet orchids (Corybas) to clarify the taxonomic and conservation status of the threatened species Corybas dowlingii, a narrow endemic from southeast Australia. Taxonomic delimitation between the three closely related species C. aconitiflorus, C. barbarae, and C. dowlingii has been mainly based on floral traits which exhibit varying degrees of overlap, rendering species delimitation in the complex difficult. Genome-wide data for the species complex was generated using double-digest restriction-site associated DNA (ddRAD) sequencing. Phylogenomic, genetic network and genetic structure analysis were carried out as well as co-ancestry analysis and hybridisation detection analysis. The ddRADseq results exhibited fine scale genetic structure within the C. acotiniflorus complex and provided evidence for hybridisation and introgression within the complex, resulting in blurred taxonomic boundaries between the three species. Implications of the results for conservation management in the face of hybridisation are discussed
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
) and revealed multiple evolution of dwarf shrubs
No full textThe large and diverse genus Salix L. is of particular interest for decades of biological research. However, despite the morphological plasticity, the reconstruction of phylogenetic relationships was so far hampered by the lack of informative molecular markers. Infrageneric classification based on morphology separates dwarf shrubs (subg. Chamaetia) and taller shrubs (subg. Vetrix), while previous phylogenetic studies placed species of these two subgenera just in one largely unresolved clade. Here we want to test the utility of genomic RAD sequencing markers for resolving relationships at different levels of divergence in Salix. Based on a sampling of 15 European species representing 13 sections of the two subgenera, we used five different RAD sequencing datasets generated by ipyrad to conduct phylogenetic analyses. Additionally we reconstructed the evolution of growth form and analyzed the genetic composition of the whole clade. The results showed fully resolved trees in both ML and BI analysis with high statistical support. The two subgenera Chamaetia and Vetrix were recognized as nonmonophyletic, which suggests that they should be merged. Within the Vetrix/Chamaetia clade, a division into three major subclades could be observed. All species were confirmed to be monophyletic. Based on our data, arctic-alpine dwarf shrubs evolved four times independently. The structure analysis showed five mainly uniform genetic clusters which are congruent in sister relationships observed in the phylogenies. Our study confirmed RAD sequencing as a useful genomic tool for the reconstruction of relationships on different taxonomic levels in the genus Salix
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