engleski

Mediterranean centre of origin of Anemoninae (Ranunculaceae) inferred from karyotype history

Comparative cytological analyses combined with phylogeny are a powerful approach for deciphering aspects of evolutionary differentiation that are thoroughly investigated in three closely related genera Anemone, Hepatica and Pulsatilla of the worldwide distributed Anemoninae (Ranunculaceae). Chromosome number, karyotype morphology, heterochromatin distribution and 35S and 5S rDNA localization are investigated in nine Anemone, three Pulsatilla species and Hepatica nobilis. The mechanisms involved in karyotype evolution are identified and interpreted in a phylogenetic context. The basic number of all investigated taxa is 7 and 8. Karyotypes of diploid Anemone and Pulsatilla species that have the basic number 8 are uniform consisting of three pairs of acrocentrics, one pair of acro-, submeta- to metacentric chromosomes, and four pairs of metacentric chromosomes. One to three 35S and one to three 5S rDNA loci were present in diploid and polyploid taxa. 35S rDNA loci are positioned on the short arm of acrocentric chromosomes, while for 5S rDNA loci there is no preferential chromosomal position. The karyotype of A. narcisifolia, the only investigated species with x=7 is similar to the karyotype of Hepatica species with one pair of acrocentric and six pairs of metacentric chromosomes. A narcisifolia possesses a unique karyotype: a satellite positioned on the short arm of the metacentric chromosome 3. Phylogenetic tree based on the cytogenetic data generally agree with the present classification. Anemone species have undergone multiple rounds of diversification, related to the very different ages of the clades. The hypothesis of the Mediterranean centre of origin is supported and an ancestral karyotype similar to A. hortensis (x=8) is proposed. The Anemonidium subgenus (x=7) evolved via major reconstruction of the karyotype: a change in the base chromosome number from x=8 to x=7. This study shows clear evidence that this change has arisen from fusion of two acrocentric chromosomes.

35S and 5S rDNA; Anemone; fluorescence in situ hybridization (FISH); karyotype evolution; Pulsatilla

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