Over the last decade, Tunisia has been invaded by recurrent drought periods which caused an extension of desertification along the North-South axis. Accompanied with various anthropogenic factors, the low and erratic rainfall results in frequent periods of serious drought alternating with periods of floods have caused major damages in the natural forage resources. Face to this situation, The Tunisian Government has recently engaged a vast program for the management, conservation and mobilization of natural genetic resources: national strategies for soil and water conservation, water resources, forage resources and rangelands rehabilitation. Because of its great ecological, agronomic and economic properties, the genus Brachypodium, has been developed as a model for temperate cereals, biofuel and grass crop. In order to define a strategy for improving and managing genetic resources of Brachypodium species in Tunisia, we have characterized the morpho-phenologic and the genetic variation of 180 lines of the complex of species B. distachyon, B. stacei and B. hybridum through 18 quantitatives traits and a large set of SSR and InDels markers. The first results of our analysis showed that the species allotetraploid B. hybridum is the predominant species in Tunisia, while the two diploid species B. distachyon and B.stacei are less frequent. The analysis of morpho-genetic diversity of this complex of species by the 18 morpho-phenologic traits and 15 SSR markers showed that the morphogenetic variation between species dominate that within species. However, the allotetraploid species was found to be more morphologically and genetically variable its two parental species. The detailed analysis of the morpho-phenologic diversity of the Tunisian B. hybridum germplasm (9 natural populations) showed a considerable variation between populations and eco-regions in all studied traits Variation was relatively higher for reproductive (34.8 %) than for vegetative (32.8 %) traits. The majority of traits showed very low ( 0.3) heritability with low border value for average length of spikelet and an average value of 0.64. Analysis of the morpho-phenologic between populations revealed that populations originated from Ain Drahem and Jbel Zaghouan (0.61) are the most differenciated while those Haouria and Raoued are the most morphologically closes (Qst = 0.1) (Overal Qst = 0.32). Moreover, the results showed also that the morphological differentiation between populations is not affected neither by geographic distances nor altitudinal differences. The genetic variation the Tunisian B. hybridum germplasm analyzed by SSR and InDels markers showed that the studied populations of B. hybrdium are characterized by high genetic variability. The results of SSR analysis revealed 100% of polymorphism and an average of genetic diversity (expected heterozygosity) of 0.79 across populations, while those revealed by InDels markers showed that the studied populations exhibited 90% of polymorphism and 35% of genetic variation. The extensive intra-population genetic variation is accompanied by a recurrent inter-populational gene flow (Nm> 2) promoting a homogeneous intra-population genetic variation a relatively low inter-populations genetic differentiation. Indeed, the analysis of molecular variance (AMOVA) based on SSR and Indels data revealed that most of genetic variation was attributed to the within populations component. The level of genetic differentiation among populations was doesn't exceeds 2% for SSR markers (PT = 0.023) and 20% for InDels markers (PT = 0.196). Moreover, the spatial genetic structure established through Cluster analysis (UPGMA) principal co-ordinate analysis (PCoA) and Bayesian approach grouped populations from distinct geographic area and altitudinal classes, suggesting that neither geographical distances nor altitudinal differences constrain the relationships among the populations. Taken together, the results the morpho-phenologic and molecular approaches suggest that the genetic structure of the Tunisian natural populations of B. hybridum is influenced by both, a gene flow via long seed dispersal and the natural selection.
[Background] Brachypodium distachyon (Poaceae), an annual Mediterranean Aluminum (Al)-sensitive grass, is currently being used as a model species to provide new information on cereals and biofuel crops. The plant has a short life cycle and one of the smallest genomes in the grasses being well suited to experimental manipulation. Its genome has been fully sequenced and several genomic resources are being developed to elucidate key traits and gene functions. A reliable germplasm collection that reflects the natural diversity of this species is therefore needed for all these genomic resources. However, despite being a model plant, we still know very little about its genetic diversity. As a first step to overcome this gap, we used nuclear Simple Sequence Repeats (nSSR) to study the patterns of genetic diversity and population structure of B. distachyon in 14 populations sampled across the Iberian Peninsula (Spain), one of its best known areas. ; [Results] We found very low levels of genetic diversity, allelic number and heterozygosity in B. distachyon, congruent with a highly selfing system. Our results indicate the existence of at least three genetic clusters providing additional evidence for the existence of a significant genetic structure in the Iberian Peninsula and supporting this geographical area as an important genetic reservoir. Several hotspots of genetic diversity were detected and populations growing on basic soils were significantly more diverse than those growing in acidic soils. A partial Mantel test confirmed a statistically significant Isolation-By-Distance (IBD) among all studied populations, as well as a statistically significant Isolation-By-Environment (IBE) revealing the presence of environmental-driven isolation as one explanation for the genetic patterns found in the Iberian Peninsula. ; [Conclusions] The finding of higher genetic diversity in eastern Iberian populations occurring in basic soils suggests that these populations can be better adapted than those occurring in western areas of the Iberian Peninsula where the soils are more acidic and accumulate toxic Al ions. This suggests that the western Iberian acidic soils might prevent the establishment of Al-sensitive B. distachyon populations, potentially causing the existence of more genetically depauperated individuals. ; The study has been funded by two consecutive Spanish Ministry of Economy and Competitiveness grant projects (CGL2012–39953-C02–01, CGL2016–79790-P) and one Aragon Government and European Social Fund Bioflora grant to PC and IM. DL-A and VS were funded by a Spanish Ministry of Science and Innovation and a Tomsk State University PhD fellowship, respectively. DL-A was also supported by a Spanish Instituto de Estudios Altoaragoneses grant. IM received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007–2013) under REA grant agreement PIOF-GA-2011-301,257. PH was funded by Spanish Junta de Andalucia project AGR-0482. ; Peer reviewed
99 pags.- Tabls.- Figs. This is the pre-peer reviewed version of the article doi 10.1111/nph.14926 which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/nph.14926/abstract This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ; Few pan-genomic studies have been conducted in plants, and none of them have focused on the intraspecific diversity and evolution of their plastid genomes. We address this issue in Brachypodium distachyon and its close relatives B. stacei and B. hybridum, for which a large genomic data set has been compiled. We analyze inter- and intraspecific plastid comparative genomics and phylogenomic relationships within a family-wide framework. Major indel differences were detected between Brachypodium plastomes. Within B. distachyon, we detected two main lineages, a mostly Extremely Delayed Flowering (EDF+) clade and a mostly Spanish (S+) – Turkish (T+) clade, plus nine chloroplast capture and two plastid DNA (ptDNA) introgression and micro-recombination events. Early Oligocene (30.9 million yr ago (Ma)) and Late Miocene (10.1 Ma) divergence times were inferred for the respective stem and crown nodes of Brachypodium and a very recent Mid-Pleistocene (0.9 Ma) time for the B. distachyon split. Flowering time variation is a main factor driving rapid intraspecific divergence in B. distachyon, although it is counterbalanced by repeated introgression between previously isolated lineages. Swapping of plastomes between the three different genomic groups, EDF+, T+, S+, probably resulted from random backcrossing followed by stabilization through selection pressure. ; P.C., B.C-M., R.S. and D.L-A. received funding from the Spanish Ministry of Economy and Competitivity (Mineco) grant projects (CGL2012-39953-C02-01, CSIC13-4E-2490 and CGL2016-79790-P). B.C-M. was funded by Fundación ARAID. R.S. and D.L-A. were funded by their respective Spanish Mineco PhD fellowships. P.C., R.S. and D.L-A. were partially funded by a Bioflora grant cofunded by the Spanish Aragon Government and the European Social Fund. The work conducted by the US DOE Joint Genome Institute is supported by the Office of Science of the US Department of Energy under Contract no. DE-AC02-05CH11231. ; Peer reviewed
13 Pags.- 6 Figs. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder ; While prokaryotic pan-genomes have been shown to contain many more genes than any individual organism, the prevalence and functional significance of differentially present genes in eukaryotes remains poorly understood. Whole-genome de novo assembly and annotation of 54 lines of the grass Brachypodium distachyon yield a pan-genome containing nearly twice the number of genes found in any individual genome. Genes present in all lines are enriched for essential biological functions, while genes present in only some lines are enriched for conditionally beneficial functions (e.g., defense and development), display faster evolutionary rates, lie closer to transposable elements and are less likely to be syntenic with orthologous genes in other grasses. Our data suggest that differentially present genes contribute substantially to phenotypic variation within a eukaryote species, these genes have a major influence in population genetics, and transposable elements play a key role in pan-genome evolution. ; The work conducted by the US DOE Joint Genome Institute is supported by the Office of Science of the US Department of Energy under Contract no. DE-AC02-05CH11231. D.P. W. and R.A. were funded in part by the National Science Foundation (grant no. IOS–1258126), and the Great Lakes Bioenergy Research Center (Department of Energy Biological and Environmental Research Office of Science grant no. DE– FCO2–07ER64494). TEJ and DLDM were supported by NSF PGRP grant IOS-0922457. P.C. and B.C.M. were funded by Spanish MINECO (CGL2012-39953-C02-01 and CGL2016-79790-P). B.C.M. was partially funded by DGA—Obra Social La Caixa (grant number GA-LC-059-2011) and Spanish MINECO (AGL2013-48756-R, CSIC13-4E-2490). PC was partially funded by Spanish Aragon Government-European Social Fund (Bioflora). ; Peer reviewed
16 Pags.- 8 Figs. This article is licensed under a Creative Commons Attribution 4.0 International License. ; Our understanding of polyploid genome evolution is constrained because we cannot know the exact founders of a particular polyploid. To differentiate between founder effects and post polyploidization evolution, we use a pan-genomic approach to study the allotetraploid Brachypodium hybridum and its diploid progenitors. Comparative analysis suggests that most B. hybridum whole gene presence/absence variation is part of the standing variation in its diploid progenitors. Analysis of nuclear single nucleotide variants, plastomes and k-mers associated with retrotransposons reveals two independent origins for B. hybridum, ~1.4 and ~0.14 million years ago. Examination of gene expression in the younger B. hybridum lineage reveals no bias in overall subgenome expression. Our results are consistent with a gradual accumulation of genomic changes after polyploidization and a lack of subgenome expression dominance. Significantly, if we did not use a pan-genomic approach, we would grossly overestimate the number of genomic changes attributable to post polyploidization evolution. ; The work conducted by the US DOE Joint Genome Institute is supported by the Office of Science of the US Department of Energy under Contract no. DE-AC02-05CH11231 and User Agreement No. FP00006675 between the University of Zaragoza (User) and the DOE (Community Science Program 503504 proposal); S.J. was supported by the DOE Office of Science Graduate Student Research Program; P.C., B.C.-M., A.D.P., and R.S. were supported by a Spanish Ministry of Economy and Competitiveness grant CGL2016-79790-P; P.C., A.D.P., and R.S. were supported by a Bioflora A01-17 grant co-funded by the Spanish Aragon Government and the European Social Fund. R.H., E.W., and J.L. were supported by the National Science Centre Poland (grants DEC-2012/04/A/NZ3/00572 and DEC-2014/14/M/NZ2/00519). J.H.D. and C.N. were supported by Leverhulme Trust (grant no. 10754). A.C.E. and A.D. were supported by the European Research Council under the European Union's Seventh Framework Program (FP7/2007-2013)/ERC grant agreement no [GA335691 "Effectomics"], the Austrian Science Fund (FWF): [P27429-B22, P27818-B22, I 3033-B22], and the Austrian Academy of Science (OEAW). ; Peer reviewed
[Background and Aims] It is accepted that contemporary allopolyploid species have originated recurrently, but very few cases have been documented using multiple natural formations of the same species. To extend our knowledge, we have investigated the multiple origins, genetic variation and structure of the allotetraploid grass Brachypodium hybridum with respect to its progenitor diploid species B. distachyon (D genome) and B. stacei (S genome). For this, our primary focus is the Iberian Peninsula, an evolutionary hotspot for the genus Brachypodium. ; [Methods] We analysed 342 B. hybridum individuals from 36 populations using ten nuclear SSR loci and two plastid loci. The B. hybridum genetic profiles were compared with those previously reported for B. stacei and B. distachyon. In addition, phylogenetic analysis of the plastid data was performed for a reduced subset of individuals. ; [Key Results] The nuclear simple sequence repeat (SSR) genetic analysis detected medium to high genetic diversity, with a strong south-to-north genetic structure cline, and a high selfing rate in B. hybridum. Comparative genetic analysis showed a close relatedness of current B. hybridum D allelic profiles with those of B. distachyon, but a lack of similarity with those of B. stacei, suggesting another B. stacei source for the B. hybridum S alleles. Plastid analysis detected three different bidirectional allopolyploidization events: two involved distinct B. distachyon-like ancestors and one involved a B. stacei-like ancestor. The south-eastern Iberian Peninsula B. hybridum populations were more genetically diverse and could have originated from at least two hybridization events whereas north-eastern/north-western Iberian Peninsula B. hybridum populations were less diverse and may have derived from at least one hybridization event. ; [Conclusions] The genetic and evolutionary evidence supports the plausible in situ origin of the south-eastern and northern Iberian Peninsula B. hybridum allopolyploids from their respective local B. distachyon and unknown B. stacei ancestors. The untapped multiple origins and genetic variation detected in these B. hybridum populations opens the way to future evolutionary analysis of allopolyploid formation and genomic dominance and expression in the B. hybridum–B. distachyon–B. stacei grass model complex. ; This work was supported by the Spanish Ministry of Economy and Competitivity (Mineco) CGL2016-79790-P and University of Zaragoza UZ2016_TEC02 grant projects. V.S. was funded by a Russian Ministry of Science and Higher Education fellowship and grant RFBR no. 18-34-00901. P.C. and I.M. were partially funded by a European Social Fund and Aragón Government Bioflora grant.
Fungal endophytes develop inside plants without visible external signs, and they may confer adaptive advantages to their hosts. Culturing methods have been traditionally used to recognize the fungal endophytic assemblage, but novel metabarcoding techniques are being increasingly applied. This study aims to characterize the fungal endophytic assemblage in shoots, rhizomes and roots of the tall grass Brachypodium rupestre growing in a large area of natural grasslands with a continuum of anthropized disturbance regimes. Seven out of 88 taxa identified via metabarcoding accounted for 81.2% of the reads (Helotiaceae, Lachnum sp. A, Albotricha sp. A, Helotiales A, Agaricales A, Mycena sp. and Mollisiaceae C), revealing a small group of abundant endophytes and a large group of rare species. Although both methods detected the same trends in richness and fungal diversity among the tissues (root > rhizome > shoot) and grasslands (low-diversity >high-diversity grasslands), the metabarcoding tool identified 5.8 times more taxa than the traditional culturing method (15 taxa) but, surprisingly, failed to sequence the most isolated endophyte on plates, Omnidemptus graminis. Since both methods are still subject to important constraints, both are required to obtain a complete characterization of the fungal endophytic assemblage of the plant species. ; M.D. got funding through UPNA's doctorate scholarship. This research was supported by 'la Caixa' Foundation and CAN foundation (LCF/PR/PR13/51080004), Ecoembes-SEO/Birdlife (Libera 2017), Government of Navarra (STEM research project 2018) and Interreg Sudoe Programme, European Regional Development Fund, European-Union, Open2preserve Project (SOE2/P5/E0804).
Plant-soil feedback mechanisms influence the abundance and rarity of plant species and can favour invasive processes, including those of native species. To explore these mechanisms, we analysed correlations between spatial distributions of plant biomass and soil properties in two neighbouring grasslands at different phases of expansion of the native Eurasian tall-grass Brachypodium rupestre (Host) Roem & Schult (B. rupestre cover: >75 and 25–50%). For this, we applied spatially explicit sampling, geostatistical analysis and structural equation models (SEM) to probe causal relationships among measured variables involved in nutrient accumulation. We hypothesized that if litter accumulates as a result of reduced grazing, 'fertility islands' (spots of high SOM and nutrient contents) will form under B. rupestre clumps because the increase in resource inputs from litter will trigger SOM build-up and promote microbial growth. Our results show that 'fertility islands' of P and amino acids occurred under the patchy clumps of B. rupestre in the less invaded grassland. In addition, the SEMs indicated that nutrient accumulation was partially due to mineralization of the SOM and modulated by the soil microbial biomass. However, there was no correlation between spatial patterns of B. rupestre biomass, SOM and microbial biomass. Moreover, the SEMs explained small amounts of variance in them (SOM r2 = 0.22 and microbial biomass r2 = 0.08), suggesting that factors other than B. rupestre biomass were responsible for the high fertility below the patches. Our spatially explicit approach demonstrated that litter inputs in dense temperate grassland communities can generate 'fertility islands' that may favour the stability and expansion of a tall-grass invader and suggest that herbivory may enhance or inhibit this phenomenon. ; The study was funded by 'la Caixa' Foundation, Spain and CAN foundation, Spain (LCF/PR/PR13/51080004), the Ministry of Science and Innovation of the Spanish Government (project refs. CGL2010-21963, CGL2011-29746 and CGL2017-85490-R), and Interreg Sudoe Programme, European Regional Development Fund, European-Union, Open2preserve Project (SOE2/P5/E0804). L. Múgica and M. Durán were funded through a UPNA Research Staff Training Grant.
Not Available ; Iron (Fe) and Zinc (Zn) are the key elements required for many of the biological process in plants and animals. Transporter proteins are essential for uptake, transport and accumulation for Fe and Zn in plants. The present investigation was undertaken to study and compare the structural and functional diversity and evolutionary significance of the yellow stripe-like (YSL) transporters through in-silico tools in five species (barley, Brachypodium, foxtail millet, maize and rice) of Poaceae. One hundred and two YSL transporters collected from public databases were used in the analysis. All YSL transporters possessed PF03169 domain which belongs to the oligo peptide transporters (OPT) super family. Molecular weight of YSL proteins ranged from 11.10 to 84.70 kDa while pI values ranged from 4.99 to 11.64. Scondary structure analysis identified that, alpha helix and random coils were the most common structures of the YSL proteins. Phylogenetic analysis revealed that the YSL transporters are highly conserved in these five grass species. Comparative mapping of genes of YSL transporters showed maximum synteny between Brachypodium and barley (30%) followed by Brachypodium and rice (25%). Neutrality test has in fact revealed the positive or Darwinian selection on YSL transporters. The results of the present investigation provided a significant understanding of the structural and biological role of YSL transporters as well as the evolutionary pattern in Poaceae family. ; Department of Science and Technology, Government of IndiaDepartment of Science & Technology (India) [DST/INSPIRE/2011/IF110504]; ICAR-NPTC on Functional Genomics (Maize component: 21-22)
The effect of neighbouring plants on crop root system architecture may directly interfere with water and nutrient acquisition, yet this important and interesting aspect of competition remains poorly understood. Here, the effect of the weed blackgrass (Alopecurus myosuroides Huds.) on wheat (Triticum aestivum L.) roots was tested, since a low density of this species (25 plants m-2) can lead to a 10% decrease in wheat yield and herbicide resistance is problematic. We used a simplified growth system based on gelled medium, to grow wheat alongside a neighbour, either another wheat plant, a blackgrass or Brachypodium dystachion individual (a model grass). A detailed analysis of wheat seminal root system architecture showed that the presence of a neighbour principally affected the root length, rather than number or diameter under a high nutrient regime. In particular, the length of first order lateral roots decreased significantly in the presence of blackgrass and Brachypodium. However, this effect was not noted when wheat plants were grown in low nutrient conditions. This suggests that wheat may be less sensitive to the presence of blackgrass when grown in low nutrient conditions. In addition, nutrient availability to the neighbour did not modulate the neighbour effect on wheat root architecture. ; This work was supported by European Union FP7 Marie Curie International Reintegration Grant, the Gatsby Charitable Foundation, the Broodbank Trust and the Newton Trust University of Cambridge.
[Introduction] Ribosomal DNA (rDNA) loci have been widely used for identification of allopolyploids and hybrids, although few of these studies employed high-throughput sequencing data. Here we use graph clustering implemented in the RepeatExplorer (RE) pipeline to analyze homoeologous 5S rDNA arrays at the genomic level searching for hybridogenic origin of species. Data were obtained from more than 80 plant species, including several well-defined allopolyploids and homoploid hybrids of different evolutionary ages and from widely dispersed taxonomic groups. [Results] (i) Diploids show simple circular-shaped graphs of their 5S rDNA clusters. In contrast, most allopolyploids and other interspecific hybrids exhibit more complex graphs composed of two or more interconnected loops representing intergenic spacers (IGS). (ii) There was a relationship between graph complexity and locus numbers. (iii) The sequences and lengths of the 5S rDNA units reconstituted in silico from k-mers were congruent with those experimentally determined. (iv) Three-genomic comparative cluster analysis of reads from allopolyploids and progenitor diploids allowed identification of homoeologous 5S rRNA gene families even in relatively ancient (c. 1 Myr) Gossypium and Brachypodium allopolyploids which already exhibit uniparental partial loss of rDNA repeats. (v) Finally, species harboring introgressed genomes exhibit exceptionally complex graph structures. [Conclusion] We found that the cluster graph shapes and graph parameters (k-mer coverage scores and connected component index) well-reflect the organization and intragenomic homogeneity of 5S rDNA repeats. We propose that the analysis of 5S rDNA cluster graphs computed by the RE pipeline together with the cytogenetic analysis might be a reliable approach for the determination of the hybrid or allopolyploid plant species parentage and may also be useful for detecting historical introgression events. ; The work was supported by the Czech Science Foundation (grant 19-03442S), the Polish OPUS project of the National Science Centre (2018/31/B/NZ3/01761) and by the Dirección General de Investigación Científica y Técnica (CGL2016-75694-P AEI/FEDER, UE) from the government of Spain. SG benefited from a Ramón y Cajal contract (RYC-2014-16608) from the government of Spain. ; Abstract Introduction Results Relationship Between Cluster Graph Topology and Intragenomic Diversity of 5S rDNA Tracking the Origin of 5S rDNA Families in Gossypium, Brachypodium, and Spartina Allopolyploids and Homoploid Hybrids by Comparative Cluster Analysis Comparative Analysis Reveals Genetic Complexity in Species With Cryptic Introgression Histories Quantification of 5S and 35S rDNA Homoeologs in Gossypium and Brachypodium Allotetraploids From High-Throughput Sequencing Data Reconstitution of 5S rDNA Units and Gene Copy Number in Gossypium Allotetraploids Southern Blot Hybridization Analysis of 5S rDNA in Spartina Discussion Dynamism of rDNA Loci in Hybrid Genomes Evaluation of the Graph-Based Method for Identification of Allopolyploids and Hybrids Concluding Remarks Materials and Methods DNA Isolation, High-Throughput Sequencing, and Read Archive Accessions In Silico Identification of 5S rDNA Repeats Identification and Quantification of Homoeologous 5S rRNA Gene Families Statistical Methods Southern Blot Hybridization Data Availability Statement Author Contributions Funding Conflict of Interest Acknowledgments Supplementary Material References
We performed a survey of grassland communities in the Ukrainian Carpathians with the aim of: (1) syntaxonomically classifying the meso- and subxerophilous grassland vegetation; (2) analysing the main gradients in their species composition; (3) estimating the effect of selected environmental factors on grassland species composition; (4) assessing the species richness of vascular plants and bryophytes in relation to the measured environmental variables. We collected 46 phytosociological relevés during the growing seasons of 2010 and 2011. Species composition and species richness were studied at two spatial scales (1 m² and 16 m²) in relation to soil parameters (soil depth, pH (KCl), content of P, K, Mg, N and C), management regime (mowing, grazing, ploughing in the past and burning), and other factors (altitude, litter cover, open soil, inclination, solar radiation and animal excrement). Seven grassland types were distinguished belonging to 3 classes and 4 alliances, namely the Nardetea strictae including the Violion caninae (mesic pastures at altitudes of 400–600 m mostly on moderate slopes) and the Nardo strictae-Agrostion tenuis (grasslands on moderate slopes at altitudes of 700–900 m usually managed by mowing and grazing the aftermath); the Molinio-Arrhenatheretea, including the Arrhenatherion elatioris (submontane grasslands originated mostly on former fields after their abandonment in the past) and the Cynosurion cristati (intensive pastures); and the Festuco-Brometea including the Cirsio-Brachypodion pinnati (abandoned grasslands dominated by Brachypodium pinnatum and Inula salicina). Detrended correspondence analysis indicated that the major compositional turnover was related to altitude and soil reaction. A canonical correspondence analysis confirmed that altitude had the strongest effect on species composition in the analysed dataset, followed by management treatments (former ploughing, grazing intensity). For vascular plant species richness, regression tree analysis identified grazing intensity as the most important predictor at the 1 m² scale. At the 16 m² scale, soil humus content was evaluated as the most important predictor of vascular plant species richness, followed by litter cover and grazing intensity. The number of bryophytes was not determined by the studied environmental factors at either of the two spatial scales. Although the number of analysed relevés in this study was limited, our results significantly contribute to the understanding of submontane grasslands in the Ukrainian Carpathians. ; Einleitung: In den ukrainischen Karpaten existieren noch große Flächen naturnahen Graslands, das größtenteils von Hand gemäht oder beweidet wird. Das Gebiet besitzt eine hohe Biodiversität die sich im Grasland stark konzentriert. Das landwirtschaftliche System in den ukrainischen Karpaten entspricht dem high nature value farming, einem Konzept der EU-Agrarpolitik zum Erhalt einer hohen Biodiversität auf landwirtschaftlichen Flächen (BEAUFOY 2007, NUPPENAU et al. 2011). Bislang war das naturnahe Grasland der ukrainischen Karpaten pflanzensoziologisch kaum untersucht. Daher erstellten wir dort in den Jahren 2010 und 2011 insgesamt 46 Vegetationsaufnahmen um (1) das meso- und subxero-phile naturnahe Grasland syntaxonomisch einzuordnen, (2) die floristischen Hauptgradienten zu analysieren und ökologisch zu interpretieren, und um den Einfluss verschiedener Umweltfaktoren auf (3) die Artenzusammensetzung und (4) den Artenreichtum der Gefäßpflanzen und Moose einzuschätzen. Untersuchungsgebiet: Die Studie wurde in folgenden Regionen der ukrainischen Karpaten durchgeführt: Zakarpatska Oblast-Mizhhirskyi Rayon, Volovetskyi Rayon, Khuststkyi Rayon, Rayon und Tyachivskyi Rakhivskyi Rayon, Ivano-Frankovskaja Oblast-Dolynskyi Rayon und Lvivska oblast Skolivskyi Rayon (Abb. 2). Das Ausgangsgestein in den ukrainischen Karpaten wird von wechselnden Schichten des Flysch-Schiefers und Flysch-Sandsteins gebildet; kleinräumig existiert auch Kalkstein oder Granit. Das Klima ist gemäßigt kontinental. Das Untersuchungsgebiet gehört zu den unteren Karpaten mit moderat-hohen Gipfeln (bis 2061 m ü. NN: Hoverla). Die hier präsentierten Vegetationsaufnahmen wurden in Höhenlagen von 137–927 m ü. NN erstellt. Methoden: Während der Vegetationsperiode 2010 und 2011 wurden 46 Vegetationsaufnahmen nach der Braun-Blanquet-Methode mit allen Gefäßpflanzen- und Moosarten erstellt. Die Vegetation wurde auf 1 m²- und 16 m² (4 × 4 m)-Flächen aufgenommen, wobei die 1 m²-Flächen innerhalb der 16 m²-Flächen lagen. Auf den 1 m²-Flächen wurde die Deckung der Arten in Prozentschritten geschätzt während auf den 16 m²-Flächen die neunstufige Braun-Blanquet-Skala verwendet wurde. Für jede Aufnahmefläche wurden die folgenden Bodenparameter und Standortmerkmale erfasst: Bodentiefe, pH (KCl), Gehalte an P, K, Mg, N und C, aktuelle Landnutzung (Mahd, Beweidung, Abbrennen) sowie frühere Ackernutzung, Meereshöhe, Streudeckung, Deckung offener Boden, Hangneigung, Trockenheit und die Präsenz von Tierexkrementen. Die Vegetationsaufnahmen wurden in JUICE 7.0.98 analysiert (TICHÝ 2002, TICHÝ & HOLT 2006). Die Deckungswerte wurden vor den Analysen quadratwurzel-transformiert und die Vegetationsaufnahmen anschließend mit der Ward-Methode mit relativen euklidischen Distanzen analysiert. Eine mit dem Programm CANOCO 4.5 (TER BRAAK & ŠMILAUER 2002) durchgeführte Gradientenanalyse sollte Unterschiede in der Artenzusammensetzung zwischen den Vegetationseinheiten visualisieren. Beziehungen zwischen dem Artenreichtum der Gefäßpflanzen und Moose und 17 Umweltvariablen wurden mit Hilfe von Regressionsbäumen analysiert (BREIMAN et al. 1984). Ergebnisse: Sieben Vegetationstypen aus drei Klassen und vier Ordnungen wurden unterschieden (Beilage S1): Klasse Nardetea strictae → Ordnung Nardetalia strictae → Verbände Violion caninae (Weiden in Höhenlagen von 400–600 m vorwiegend an sanften Hängen) und Nardo strictae-Agrostion tenuis (in Höhenlagen von 700–900 m an sanften Hängen; in der Regel gemäht und anschließend beweidet). Klasse: Molinio-Arrhenatheretea → Ordnung Arrhenatheretalia → Verbände Arrhenatherion elatioris (submontane Wiesen, vorwiegend auf früheren Ackerflächen) und Cynosurion cristati (Inten-sivweiden); Klasse Festuco-Brometea → Ordnung Brachypodietalia → Verband Cirsio-Brachypodion pinnati (Brachen mit Dominanz von Brachypodium pinnatum und Inula salicina). Korrelationen der DCA-Ordinationsachsen mit Ellenberg-Zeigerwerten, Bodenvariablen und Land-nutzungstypen deuteten auf die Meereshöhe und den pH-Wert des Bodens als wichtigste Umweltfaktoren für die Vegetation hin (Abb. 6). Eine kanonische Korrespondenzanalyse (CCA) deutete ebenfalls auf die Meereshöhe als wichtigste Umweltvariable hin, gefolgt von den Landnutzungsvariablen ehemalige Ackernutzung und Beweidungsintensität sowie pH-Wert des Bodens, Abbrennen sowie Phosphor- und Magnesiumgehalt (Tab. 3). Der Gefäßpflanzenartenreichtum war auf den 1 m²-Flächen am stärksten mit der Beweidungsintensität korreliert (Abb. 8) und auf den 16 m²-Flächen mit dem Bodenhumusgehalt, der Streudeckung und Beweidungsintensität (Abb. 9A). Der Moosartenreichtum konnte auf keiner der beiden Raumskalen durch die untersuchten Umweltfaktoren erklärt werden. Am artenreichsten (im Mittel 61 Gefäßpflanzentaxa pro 16 m²) waren montane, regelmässig gemähte Wiesen, die offenbar niemals als Acker genutzt worden waren oder auch nicht intensiv beweidet wurden. Wiesen auf ehemaligen Ackerstandorten zeigten mit 52 Taxa einen mittleren Gäßpflanzenartenreichtum (Tab. 2) während Weiden des Violion caninae und Nardo-Agrostion am artenärmsten waren (45 bzw. 43 Taxa; Abb. 7). Diskussion: Ein direkter Vergleich unserer phytosoziologischen Einteilung mit bereits aus dem Untersuchungsgebiet publizierten Syntaxa wurde nicht vorgenommen, da die betreffenden ukrainischen Pflanzensoziologen einen anderen Klassifikationsansatz, eine andere Skala bei der Schätzung der De-ckungsgrade sowie grössere Aufnahmeflächen (100 m² bis ≥400 m²) verwendet haben. Mit dieser Methodik wurden in den letzten 10 Jahren die Vegetationstypen einiger Nationalparks und Naturschutzgebiete in den ukrainischen Karpaten pflanzensoziologisch klassifiziert (CHORNEY et al. 2005, KLIMUK et al. 2006, TOKARYUK et al. 2009, DERZHYPILSKY et al. 2011). Die Ergebnisse der Studien entsprechen jedoch nur teilweise unseren Einheiten. Schlussfolgerungen: Naturnahes Grasland bildet einen prägenden Bestandteil der Vegetation der Karpaten. Ihre größte Bedrohung sind Änderungen der traditionellen Landnutzung, vor allem aber die Aufgabe der Landnutzung überhaupt. In einigen Regionen ist Intensivierung (meist Überweidung) ein Problem wodurch die Diversität des Graslands erodiert und die Wiesen degradieren. Trotz dieser negativen Entwicklungen stellen die ukrainischen Karpaten für naturnahes Graslands immer noch eine naturschutzfachlich sehr wertvolle Region dar. Die Erkenntnisse dieser Studie sollen zur besseren Kenntnis und zum besseren Verständnis der unterschiedlichen Graslandtypen der Region beitragen.
