title: The striking and unexpected cytogenetic diversity of genus Tanacetum L. (Asteraceae): a cytometric and fluorescent in situ hybridisation study of Iranian taxa.
abstract: 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.
authors.affiliation: Department of Biology, Faculty of Basic Science, Malayer University, Malayer, Iran. n.olanj@malayeru.ac.ir.|Laboratori de Botànica - Unitat associada CSIC, Facultat de Farmàcia, Universitat de Barcelona, Avinguda Joan XXIII s/n, 08028, Barcelona, Catalonia, Spain. n.olanj@malayeru.ac.ir.
authors.forename: Nayyereh
authors.initials: N
authors.lastname: Olanj
authors.affiliation: Institut Botànic de Barcelona (IBB-CSIC-ICUB), Passeig del Migdia s/n, Parc de Montjuïc, 08038, Barcelona, Catalonia, Spain. tgarnatje@ibb.csic.es.
authors.forename: Teresa
authors.initials: T
authors.lastname: Garnatje
authors.affiliation: Department of Biology, Medicinal Plants and Drugs Research Institute, Shahid Beheshti University, Evin, 1983963113, Tehran, Iran. a-sonboli@sbu.ac.ir.
authors.forename: Ali
authors.initials: A
authors.lastname: Sonboli
authors.affiliation: Laboratori de Botànica - Unitat associada CSIC, Facultat de Farmàcia, Universitat de Barcelona, Avinguda Joan XXIII s/n, 08028, Barcelona, Catalonia, Spain. joanvalles@ub.edu.
authors.forename: Joan
authors.initials: J
authors.lastname: Vallès
authors.affiliation: Laboratori de Botànica - Unitat associada CSIC, Facultat de Farmàcia, Universitat de Barcelona, Avinguda Joan XXIII s/n, 08028, Barcelona, Catalonia, Spain. soniagarcia@ibb.csic.es.
authors.forename: Sònia
authors.initials: S
authors.lastname: Garcia
mesh_terms: D005075:Biological Evolution; D018744:DNA, Plant / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics*; D005456:Fluorescent Dyes / Q000737:chemistry; D059646:Genome Size; D018745:Genome, Plant; D017404:In Situ Hybridization, Fluorescence; D007492:Iran; D011123:Polyploidy; D031203:Tanacetum / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D004275:DNA, Ribosomal; D005456:Fluorescent Dyes