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11 p., gráf., tablas ; In higher eukaryotes, the 5S rRNA genes occur in tandem units and are arranged either separately (S-type arrangement) or linked to other repeated genes, in most cases to rDNA locus encoding 18S–5.8S–26S genes (L-type arrangement). Here we used Southern blot hybridisation, PCR and sequencing approaches to analyse genomic organisation of rRNA genes in all large gymnosperm groups, including Coniferales, Ginkgoales, Gnetales and Cycadales. The data are provided for 27 species (21 genera). The 5S units linked to the 35S rDNA units occur in some but not all Gnetales, Coniferales and in Ginkgo (~30% of the species analysed), while the remaining exhibit separate organisation. The linked 5S rRNA genes may occur as single-copy insertions or as short tandems embedded in the 26S–18S rDNA intergenic spacer (IGS). The 5S transcript may be encoded by the same (Ginkgo, Ephedra) or opposite (Podocarpus) DNA strand as the 18S–5.8S–26S genes. In addition, pseudogenised 5S copies were also found in some IGS types. Both L- and S-type units have been largely homogenised across the genomes. Phylogenetic relationships based on the comparison of 5S coding sequences suggest that the 5S genes independently inserted IGS at least three times in the course of gymnosperm evolution. Frequent transpositions and rearrangements of basic units indicate relatively relaxed selection pressures imposed on genomic organisation of 5S genes in plants. ; This work has been supported by the Spanish and Catalan governments (projects CGL2010-22234-C02-01 and 02/BOS, and project 2009SGR00439, respectively), Academy of Sciences of the Czech Republic (RVO68081707) and the Czech Science Foundation (P501/13/10057S; P501/12/G090). SG benefited from a Beatriu de Pino's postdoctoral contract with the support of the Comissionat per a Universitats i Recerca (CUR) del Departament d'Economia i Coneixement (Catalan government) ; Peer reviewed

[Background] In plants, the 5 S rRNA genes usually occur as separate tandems (S-type arrangement) or, less commonly, linked to 35 S rDNA units (L-type). The activity of linked genes remains unknown so far. We studied the homogeneity and expression of 5 S genes in several species from family Asteraceae known to contain linked 35 S-5 S units. Additionally, their methylation status was determined using bisulfite sequencing. Fluorescence in situ hybridization was applied to reveal the sub-nuclear positions of rDNA arrays. ; [Results] We found that homogenization of L-type units went to completion in most (4/6) but not all species. Two species contained major L-type and minor S-type units (termed Ls-type). The linked genes dominate 5 S rDNA expression while the separate tandems do not seem to be expressed. Members of tribe Anthemideae evolved functional variants of the polymerase III promoter in which a residing C-box element differs from the canonical angiosperm motif by as much as 30%. On this basis, a more relaxed consensus sequence of a plant C-box: (5'-RGSWTGGGTG-3') is proposed. The 5 S paralogs display heavy DNA methylation similarly as to their unlinked counterparts. FISH revealed the close association of 35 S-5 S arrays with nucleolar periphery indicating that transcription of 5 S genes may occur in this territory. ; [Conclusions] We show that the unusual linked arrangement of 5 S genes, occurring in several plant species, is fully compatible with their expression and functionality. This extraordinary 5 S gene dynamics is manifested at different levels, such as variation in intrachromosomal positions, unit structure, epigenetic modification and considerable divergence of regulatory motifs. ; This research was funded by the Grant Agency of the Czech Republic (P501-10-0208 and P501/12/G090), Academy of Science CZ (RVO68081707) and by the Spanish and Catalan governments (projects CGL2010-22234-C02-01 and 02/BOS, and project 2009SGR00439, respectively). SG benefited from a Beatriu de Pinós postdoctoral contract with the support of the Comissionat per a Universitats i Recerca (CUR) del Departament d'Economia i Coneixement de la Generalitat de Catalunya (Catalan government), and from a Short-term EMBO (European Molecular Biology Organization) fellowship. ; Peer reviewed

The Genome Size in Asteraceae Database (GSAD, http://www.asteraceaegenomesize.com) has been recently updated, with data from papers published or in press until July 2018. This constitutes the third release of GSAD, currently containing 4350 data entries for 1496 species, which represent a growth of 22.52% in the number of species with available genome size data compared with the previous release, and a growth of 57.72% in terms of entries. Approximately 6% of Asteraceae species are covered in terms of known genome sizes. The number of source papers included in this release (198) means a 48.87% increase with respect to release 2.0. The significant data increase was exploited to study the genome size evolution in the family from a phylogenetic perspective. Our results suggest that the role of chromosome number in genome size diversity within Asteraceae is basically associated to polyploidy, while dysploidy would only cause minor variation in the DNA amount along the family. Among diploid taxa, we found that the evolution of genome size shows a strong phylogenetic signal. However, this trait does not seem to evolve evenly across the phylogeny, but there could be significant scale and clade-dependent patterns. Our analyses indicate that the phylogenetic signal is stronger at low taxonomic levels, with certain tribes standing out as hotspots of autocorrelation between genome size and phylogeny. Finally, we also observe meaningful associations among nuclear DNA content on Asteraceae species and other phenotypical and ecological traits (i.e. plant habit and invasion ability). Overall, this study emphasizes the need to continue generating and analysing genome size data in order to puzzle out the evolution of this parameter and its many biological correlates. ; This work was supported by the Dirección General de Investigación Científica y Técnica (Spanish Government; projects CGL2013– 49097-C2, CGL2016-75694/P AEI/FEDER, UE and CGL2017- 84297-R AEI/FEDER, UE and the Generalitat de Catalunya ("Ajuts a grups de recerca consolidats" 2017SGR01116). S.G. benefitted from a Ramón y Cajal contract (RYC-2014-16608) from the government of Spain.

1020–1030 p., tablas, gráficos, diagrama -- Postprint del artículo publicado en Plant Journal. Versión revisada y corregida ; The online resource http://www.plantrdnadatabase.com/ stores information on the number, chromosomal locations and structure of the 5S and 18S-5.8S-26S (35S) ribosomal DNAs (rDNA) in plants. This resource was exploited to study relationships between rDNA locus number, distribution, the occurrence of linked (Ltype) and separated (S-type) 5S and 35S rDNA units, chromosome number, genome size and ploidy level. The analyses presented summarise current knowledge on rDNA locus numbers and distribution in plants. We analysed 2949 karyotypes, from 1791 species and 86 plant families, and performed ancestral character state reconstructions. The ancestral karyotype (2n = 16) has two terminal 35S sites and two interstitial 5S sites, while the median (2n = 24) presents four terminal 35S sites and three interstitial 5S sites. Whilst 86.57% of karyotypes show S-type organisation (ancestral condition), the L-type arrangement has arisen independently several times during plant evolution. A non-terminal position of 35S rDNA was found in about 25% of single-locus karyotypes, suggesting that terminal locations are not essential for functionality and expression. Single-locus karyotypes are very common, even in polyploids. In this regard, polyploidy is followed by subsequent locus loss. This results in a decrease in locus number per monoploid genome, forming part of the diploidisation process returning polyploids to a diploid-like state over time. ; This work was supported by the Dirección General de Investigación Científica y Técnica, government of Spain (CGL2013-49097-C2-2-P), the Generalitat de Catalunya, Government of Catalonia ('Ajuts a grups de recerca consolidats', 2014SGR514), the IRBIO ('Institut de Recerca en Biodiversitat'), the Czech Science Foundation (P506-16-02149J) and NERC (UK). SG benefits from a Ramón y Cajal contract from the government of Spain. ; Peer reviewed

18 p., il. ; Background: In flowering plants and animals the most common ribosomal RNA genes (rDNA) organisation is that in which 35S (encoding 18S-5.8S-26S rRNA) and 5S genes are physically separated occupying different chromosomal loci. However, recent observations established that both genes have been unified to a single 35S-5S unit in the genus Artemisia (Asteraceae), a genomic arrangement typical of primitive eukaryotes such as yeast, among others. Here we aim to reveal the origin, distribution and mechanisms leading to the linked organisation of rDNA in the Asteraceae by analysing unit structure (PCR, Southern blot, sequencing), gene copy number (quantitative PCR) and chromosomal position (FISH) of 5S and 35S rRNA genes in ~200 species representing the family diversity and other closely related groups. Results: Dominant linked rDNA genotype was found within three large groups in subfamily Asteroideae: tribe Anthemideae (93% of the studied cases), tribe Gnaphalieae (100%) and in the "Heliantheae alliance" (23%). The remaining five tribes of the Asteroideae displayed canonical non linked arrangement of rDNA, as did the other groups in the Asteraceae. Nevertheless, low copy linked genes were identified among several species that amplified unlinked units. The conserved position of functional 5S insertions downstream from the 26S gene suggests a unique, perhaps retrotransposon-mediated integration event at the base of subfamily Asteroideae. Further evolution likely involved divergence of 26S-5S intergenic spacers, amplification and homogenisation of units across the chromosomes and concomitant elimination of unlinked arrays. However, the opposite trend, from linked towards unlinked arrangement was also surmised in few species indicating possible reversibility of these processes. Conclusions: Our results indicate that nearly 25% of Asteraceae species may have evolved unusual linked arrangement of rRNA genes. Thus, in plants, fundamental changes in intrinsic structure of rDNA units, their copy number and chromosomal organisation may occur within relatively short evolutionary time. We hypothesize that the 5S gene integration within the 35S unit might have repeatedly occurred during plant evolution, and probably once in Asteraceae. ; This research was funded by the Grant Agency of the Czech Republic (P501-10-0208), the Academy of Sciences of the Czech Republic (AVOZ50040507 and AVOZ50040702, MSMT LC0604), and the Ministry of Innovation and Science of Spain, MICINN (CGL2007-64839-C02/BOS). S. G. was granted a JAE-DOC contract from the CSIC (Superior Council of Scientific Investigations) and a José Castillejo Grant from the MICINN of the Spanish Government. ; Peer reviewed

Ribosomal DNA (rDNA) loci encoding 5S and 45S (18S-5.8S-28S) rRNAs are important components of eukaryotic chromosomes. Here, we set up the animal rDNA database containing cytogenetic information about these loci in 1343 animal species (264 families) collected from 542 publications. The data are based on in situ hybridisation studies (both radioactive and fluorescent) carried out in major groups of vertebrates (fish, reptiles, amphibians, birds, and mammals) and invertebrates (mostly insects and mollusks). The database is accessible online at www.animalrdnadatabase.com. The median number of 45S and 5S sites was close to two per diploid chromosome set for both rDNAs despite large variation (1–74 for 5S and 1–54 for 45S sites). No significant correlation between the number of 5S and 45S rDNA loci was observed, suggesting that their distribution and amplification across the chromosomes follow independent evolutionary trajectories. Each group, irrespective of taxonomic classification, contained rDNA sites at any chromosome location. However, the distal and pericentromeric positions were the most prevalent (> 75% karyotypes) for 45S loci, while the position of 5S loci was more variable. We also examined potential relationships between molecular attributes of rDNA (homogenisation and expression) and cytogenetic parameters such as rDNA positions, chromosome number, and morphology. ; The Czech Science Foundation (P506/16/02149J) and the Dirección General de Investigación Científica y Técnica from the Government of Spain (CGL2016-75694-P) are acknowledged for funding. JS participates on the PhD program Functional Genomics at the Masaryk University, Brno, CZ. SG benefits from a "Ramón y Cajal" contract from the Government of Spain. ; Peer reviewed

7 p., gráficos -- versión online previa sin paginación -- post-print del artículo publicado en Plant Systematics and Evolution. Versión revisada y corregida ; Here we present the third release of the plant rDNA database (March 2017), an open access online resource with information on numbers, locations and structure of 5S and 18S-5.8S-26S (35S) ribosomal DNA (rDNA) (www.plantrdnadatabase.com). Data are now available for 2148 species (3783 entries), extracted from 785 papers published until the end of 2016. This means an expansion of 33.5% in terms of new species and 13% in new publications consulted. We appreciate an increased interest on rDNA loci research in recent years, since 10.78% of all data available were published only in 2016. The database has been expanded to include information on telomere composition and on species whose genome has been fully sequenced up to date. Telomere sequence is only known with certainty for 9.60% of species in the database and for 36.79% at the genus level, indicating, potentially, that the consensus plant telomere (Arabidopsis-type) might not be as extended as previously thought. We have also introduced the taxonomic category order as an additional option for data browsing. Similarly, we have included a new category to indicate the hybrid status of taxa. In addition, we upgraded and/or proofread tabs and links and slightly modified the website for a more dynamic appearance. This manuscript provides a synopsis of these changes and developments. ; The Dirección General de Investigación Científica y Técnica from the Government of Spain (CGL2016-75694-P), the Czech Science Foundation (P506/16/02149 J) and the Government of Catalonia ("Ajuts a grups de recerca consolidats", 2014SGR514) are acknowledged for funding. Sònia Garcia benefits from a "Ramón y Cajal" contract from the Government of Spain (RYC-2014-16608). ; Peer reviewed

1 p. -- Corrección de erratas detectadas en el artículo original "Third release of the plant rDNA database with updated content and information on telomere composition and sequenced plant" (https://doi.org/10.1007/s00606-017-1440-9 / http://hdl.handle.net/10261/153691) -- ; The Dirección General de Investigación Científica y Técnica from the Government of Spain (CGL2016-75694-P), the Czech Science Foundation (P506/16/02149 J) and the Government of Catalonia ("Ajuts a grups de recerca consolidats", 2014SGR514) are acknowledged for funding. Sònia Garcia benefits from a "Ramón y Cajal" contract from the Government of Spain (RYC-2014-16608). ; Peer reviewed

Editors: Diego Muñoz-Torrero, M. Pilar Vinardell and Javier Palazón. ; Here we present an overview on the results of eight years of research line devoted to the organisation, expression and evolution of rRNA genes in plant genomes. We describe how we discovered a new rDNA arrangement in genus Artemisia, which includes all rRNA genes in a single unit (L-type). This was the first time that such organisation was found in seed plants. We further explored family Asteraceae in depth, to which Artemisia belongs, to find that the L-type arrangement may be present in about 25% of its species. Later on we move to gymnosperms to describe the landscape of rRNA arrangements in a representative sample of its diversity. We assess the expression rate of the L-type rRNA in several L-type species, which is comparable to that of species with separated arrangement of rRNA genes (S-type). Finally, we present the resource www.plantrdnadatabase.com which includes information on type of rDNA arrangement, number and position of rDNA loci in plants. ; This work was supported by Ministry of Economy and Competitiveness from the Government of Spain (CGL2010-22234-C02-01,02/BOS and CGL2013-49097-C2-2-P), the Generalitat de Catalunya, Government of Catalonia ("Ajuts a grups de recerca consolidats", 2009SGR0439 and 2014SGR514) and the IRBio (Institut de Recerca de la Biodiversitat, Universitat de Barcelona). SG benefited from a ―Ramón y Cajal‖ researcher contract of the Ministry of Economy and Competitiveness from the Government of Spain. ; Peer reviewed

[Background] Although karyologically well studied, the genus Tanacetum (Asteraceae) is poorly known from the perspective of molecular cytogenetics. The prevalence of polyploidy, including odd ploidy warranted an extensive cytogenetic study. We studied several species native to Iran, one of the most important centres of diversity of the genus. We aimed to characterise Tanacetum genomes through fluorochrome banding, fluorescent in situ hybridisation (FISH) of rRNA genes and the assessment of genome size by flow cytometry. We appraise the effect of polyploidy and evaluate the existence of intraspecific variation based on the number and distribution of GC-rich bands and rDNA loci. Finally, we infer ancestral genome size and other cytogenetic traits considering phylogenetic relationships within the genus. ; [Results] We report first genome size (2C) estimates ranging from 3.84 to 24.87 pg representing about 11 % of those recognised for the genus. We found striking cytogenetic diversity both in the number of GC-rich bands and rDNA loci. There is variation even at the population level and some species have undergone massive heterochromatic or rDNA amplification. Certain morphometric data, such as pollen size or inflorescence architecture, bear some relationship with genome size. Reconstruction of ancestral genome size, number of CMA+ bands and number of rDNA loci show that ups and downs have occurred during the evolution of these traits, although genome size has mostly increased and the number of CMA+ bands and rDNA loci have decreased in present-day taxa compared with ancestral values. ; [Conclusions]Tanacetum genomes are highly unstable in the number of GC-rich bands and rDNA loci, although some patterns can be established at the diploid and tetraploid levels. In particular, aneuploid taxa and some odd ploidy species show greater cytogenetic instability than the rest of the genus. We have also confirmed a linked rDNA arrangement for all the studied Tanacetum species. The labile scenario found in Tanacetum proves that some cytogenetic features previously regarded as relatively constant, or even diagnostic, can display high variability, which is better interpreted within a phylogenetic context. ; This work was supported by the Dirección General de Investigación Científica y Técnica, Government of Spain (CGL2010-22234-C02-01 and 02/BOS and CGL2013-49097-C2-2-P) and the Generalitat de Catalunya, Government of Catalonia (>Ajuts a grups de recerca consolidats>, 2009SGR0439 and 2014SGR514). SG benefitted from a Juan de la Cierva postdoctoral contract from the Ministry of Economy and Competitiveness, Government of Spain. NO benefitted from a fellowship from the Science, Research and Technology Ministry of Iran. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI) ; Peer Reviewed

11 p., fig. -- Post-print del artículo publicado en Botanical Journal of the Linnean Society. Versión revisada y corregida. ; Fluorescence in situ hybridization (FISH) with 35S and 5S rDNA probes was used to characterize cytogenetically representatives of Artemisia subgenus Dracunculus and allied species and to explore their evolution following polyploidization. At the diploid level two rDNA loci were observed in most species belonging to the A. dracunculus complex, a pattern considered to be the ancestral state for diploid Artemisia. In contrast, representative species from the Eurasian grade which belong to the other major lineage of the subgenus had more heterogeneous rDNA profiles, with three to five loci at the diploid level. Divergent patterns of locus evolution were also detected in polyploids, with the number and distribution of rDNA loci broadly fitting the two main diversification lineages in the subgenus. In the polyploid complex of A. dracunculus, the number of rDNA loci was almost proportional to ploidy, although monoploid genome size was shown to decrease with increasing ploidy. However, in polyploids from the Eurasian grade we found a remarkable reduction in the number of rDNA sites, suggesting that these species might have experienced either a complete loss of loci or a significant reduction in the number of repeats following polyploid formation ; This work was subsidized by DGICYT (Spanish Government; projects CGL2007-64839-C02-01 and 02/BOS, and CGL2010-22234-C02-01 and 02/BOS) and the Catalan government (projects 2005SGR00344 and 2009SGR00439). S.G. benefited from a Beatriu de Pinós postdoctoral contract with the support of the Comissionat per a Universitats i Recerca (CUR) del Departament d'Economia i Coneixement de la Generalitat de Catalunya (Catalan government). ; Peer reviewed

This paper presents a karyological and cytogenetic characterisation of Artemisia absinthium var. absinthium and A. absinthium var. calcigena (Asteraceae, Anthemideae). Genome size (assessed as nuclear DNA amount), chromosome number, karyotype parameters, fluorochrome banding and fluorescent in situ hybridisation (FISH) of 18S–5.8S–26S and 5S rDNA were studied in Polish specimens of both varieties whose phylogenetic relationships were also established based on their molecular structure. The present study is the first with a focus on A. absinthium var. calcigena. The results basically agree with those previously reported from other A. absinthium populations and show no essential genome organization differences between the varieties. ; K. K. received a master student grant of the European Union's LLP-Socrates programme to work at the University of Barcelona, J. P. a predoctoral grant from the Spanish Government (FPI program), S. G. a postdoctoral JAE Doc contract from the CSIC, and J. V. a grant from the Universitat de Barcelona in the frame of the Erasmus programme. This work was subsidized by DGICYT — Spanish Government (projects CGL2007-64839-C02-01 and CGL2007-64839-C02-02) and by the Uniwersytet Wrocławski (grant 2600/W/IBR/06). ; Peer reviewed

8 p., tablas, fot., mapas ; [EN]Artemisia herba-alba is a largely-distributed and often landscape-dom- inating taxon in arid areas of the Mediterranean and Irano-Turanian regions. In Algeria, in 2010 its communities covered 10% of the steppe territory, but its populations have been subjected to overgrazing. A karyological study based on 22 populations together with a cytogenetic characterisation of this species has been performed for the first time in Algerian materials, through genome size and chromosome number determination. Fluorescence in situ hybridisation (FISH) was also used to assess the rDNA loci number and distribution in the two ploidy levels detected. The studied accessions are diploid (2n = 2x = 18 chromosomes, 6 populations) or tetraploid (2n = 4x = 36 chromosomes, 15 popula- tions). One population, occupying a more or less central geographic posi- tion among the studied area, presented both cytotypes. Genome size reflects well the two ploidy levels, with no evidence of downsizing with polyploidy. The karyotypes are rather symmetric (2A Stebbins' class). FISH analyses detected four signals (2 loci) in diploid and eight signals (4 loci) in tetraploid cytotypes for both ribosomal DNA genes, which present an L-type (linked) organisation, i.e. with loci from both rDNA genes colocal- ised. The presence of two ploidy levels suggest a genomic dynamism and even a possible differentiation underlying the morphological uniformity and despite the dramatic decrease experienced by this plant in Algeria in terms of surface coverage. ; [ES]Artemisia herba-alba es un taxon ampliamente distribuido y dominante en el paisaje en áreas áridas de las regiones mediterránea e irano-turania. En Argelia, sus comunidades cubrían en 2010 el 10% de su territorio de estepa, pero sus poblaciones se encuentran sometidas a sobrepastoreo. Se ha llevado a cabo un estudio cariológico basado en 22 poblaciones, se han caracterizado citogenéticamente por primera vez poblaciones argelinas de esta especie y se ha estimado el tamaño del genoma y el número cromosomático, además de la determinación por hibridación in situ fluorescente (FISH) del número y la distribución de los loci del ADN ribosómico en los dos niveles de ploidía. Las accesiones estudiadas son diploides (2n = 2x = 18, 6 poblaciones) o tetraploides (2n = 4x = 36, 15 poblaciones), y una, que ocupa una posición más o menos céntrica entre las consideradas, presenta ambos niveles de ploidía. El tamaño del genoma refleja los dos niveles de ploidía y no se observan indicios de disminución con la poliploidía. Los cariotipos son simétricos (clase 2A de Stebbins). Los análisis de FISH detectan cuatro señales (2 loci) en los citoti- pos diploides y ocho señales (4 loci) en los tetraploides para ambos genes del ADN ribosómico, que presenta una organización del tipo L (ligada), es decir, con los loci de los dos genes del ADNr colocalizados. La pres- encia de dos niveles de ploidía sugiere un dinamismo genético e incluso una posible diferenciación más allá de la uniformidad morfológica, con independencia del retroceso experimentado por esta planta en Argelia. ; This work was supported by the Dirección General de Investigación Científica y Técnica, Spanish government (CGL2013-49097-C2-2-P) and the Generalitat de Catalunya, Catalonian government ("Ajuts a grups de recerca consolidats", 2014SGR514). Y.B. received a grant from the Algerian government for two short stages in coauthors' laboratories in Barcelona. S.G. benefitted from a Juan de la Cierva and Ramón y Cajal contracts from the Ministry of Economy and Competitiveness, Government of Spain. ; Peer reviewed

Genome size of 18 species of the genus Carduncellus, two species of the related genus Phonus and the monotypic genus Femeniasia (F. balearica) has been assessed by flow cytometry for the first time. Ploidy levels were assigned using genome size data together with previously reported chromosome counts. A phylogenetic framework was built to visualize how cytogenetic traits distributed across taxa. The results confirmed three ploidy levels (2x, 4x and 6x), with a predominance of diploids. The 2C values ranged from 3.24 pg in Carduncellus calvus to 11.16 pg in C. eriocephalus, whereas monoploid genome size (1Cx) ranged from 1.29 pg in C. duvauxii (4x) to 2.30 pg in Phonus rhiphaeus (2x). The mean 1Cx for tetraploids was lower than for diploids. For each ploidy level, genome size values of Carduncellus, Femeniasia and Phonus were found to be higher than those of Carthamus. This result is consistent with a trend frequently observed in plants, of higher genome sizes in long life cycle taxa compared to short-lived relatives. ; El tamaño del genoma de 18 especies del género Carduncellus, dos especies de los géneros relacionados, Phonus y el género monotípico Femeniasia (F. balearica) ha sido medido por primera vez mediante citometría de flujo. Los niveles de ploidía se asignaron utilizando datos de tamaño del genoma junto con los recuentos de cromosomas previamente reportados. Se construyó un marco filogenético para visualizar la distribución de las características citogenéticas de los táxones. Los resultados confirmaron tres niveles de ploidía (2x, 4x y 6x), con un predominio de los táxones diploides. Los valores de 2C oscilaron entre 3,24 pg en Carduncellus calvus y 11,16 pg en C. eriocephalus, mientras que el tamaño del genoma monoploide (1Cx) osciló entre 1,29 pg en C. duvauxii (4x) y 2,30 pg en Phonus rhiphaeus (2x). La media de los valores 1Cx para los tetraploides fue menor que para los diploides. Los valores de tamaño del genoma de Carduncellus, Femeniasia y Phonus fueron más elevados que los de Carthamus dentro del mismo nivel de ploidía. Este resultado concuerda con una tendencia frecuentemente observada en plantas en la que los táxones con ciclos de vida largos presentan tamaños del genoma más elevados que los táxones relacionados que poseen ciclos de vida cortos. ; This work has been supported by projects from the Spanish Government [(CGL2016-75694-P (AEI/FEDER, UE)] and the Generalitat de Catalunya (2017SGR1116). SG is the holder of a Ramón y Cajal contract (RYC-2014-16608) ; INTRODUCTION MATERIALS AND METHODS Plant material DNA content assessment Phylogenetic framework Statistical analyses RESULTS AND DISCUSSION CONCLUSIONS

38 p., tablas, gráf. ; Most Calligonum species are desert plants, characteristic of the Saharan bioclimatic region. All species karyologically analyzed until present have the basic chromosome number x = 9 and comprise diploids, triploids and tetraploids. The Tunisian flora comprises diploid Calligonum arich and C. azel, of restricted distribution, and the tetraploid C. comosum with wider distribution. Analyses of their karyotypes and polyploidisation-linked rDNA changes by orcein staining, fluorochrome banding with chromomycin A3 and fluorescent in situ hybridisation with 5S and 26S ribosomal DNA probes have been performed. We report the chromosome number for Calligonum arich (2n = 18) as well as the diploid level for C. comosum for the first time. Chromosome counts have also verified the earlier described tetraploid cytotype (2n = 36) of C. comosum. A general pattern of six GC-rich bands as well as two 35S sites and four 5S sites is described for Calligonum species at the diploid level although there is intraspecific variation regarding the site number in a second type of C. comosum, with one pair of 35S rDNA sites and two pairs of 5S rDNA sites. The tetraploid cytotype of C. comosum has undergone locus loss and genome downsizing. Genome size assessments confirmed previous data. Nonetheless, statistically significant differences were found depending on the type of tissue used for estimation. Measurements from seeds had always larger values than from leaves. The presence of cytosolic compounds in leaves, interfering with DNA staining, is discussed as a possible cause of the differences. ; This work was supported by the Dirección General de Investigación Científica y Técnica, government of Spain (CGL2010-22234-C02-01/BOS and CGL2010-22234-C02-02/BOS) and the Generalitat de Catalunya, government of Catalonia (''Ajuts a grups de recerca consolidats'', 2009SGR0439). SG and OH benefitted from Juan de la Cierva postdoctoral contracts of the Ministry of Economy and Competitiveness, government of Spain. ; Peer reviewed