Chromosomal stasis in diploids contrasts with genome restructuring in auto- and allopolyploid taxa of Hepatica (Ranunculaceae).
Polyploidization and chromosomal rearrangements are recognized as major forces in plant evolution. Their role is investigated in the disjunctly distributed northern hemisphere Hepatica (Ranunculaceae). Chromosome numbers, karyotype morphology, banding patterns, 5S and 35S rDNA localization in all known species were investigated and interpreted in a phylogenetic context established from nuclear internal transcribed spacer (ITS) and plastid matK sequences. All species had a chromosome base number of x = 7. The karyotype was symmetric and showed little variation among diploids with one locus each of 5S and 35S rDNA, except for interpopulational variation concerning 35S rDNA loci number and localization in H. asiatica. Tetraploids exhibited chromosomal changes, including asymmetry and/or loss of rDNA loci. Nuclear and plastid sequences resulted in incongruent topologies because of the positions of some tetraploid taxa. The diversification of Hepatica occurred not earlier than the Pliocene. Genome restructuring, especially involving 35S rDNA, within a few million yr or less characterizes evolution of both auto- and allopolyploids and of the diploid species H. asiatica, which is the presumptive ancestor of two other diploid species.
Weiss-Schneeweiss
Hanna
H
Department of Systematic and Evolutionary Botany, and.
Schneeweiss
Gerald M
GM
Department of Biogeography and Botanical Garden, University of Vienna, Rennweg 14, A-1030 Vienna, Austria.
Stuessy
Tod F
TF
Department of Systematic and Evolutionary Botany, and.
Mabuchi
Tomoo
T
2-11-5 Sagami-ohno, Sagamihara, Kanagawa 228-0803, Japan.
Park
Jeong-Mi
JM
Department of Systematic and Evolutionary Botany, and.
Jang
Chang-Gee
CG
Department of Systematic and Evolutionary Botany, and.|Department of Biology Education, College of Education, Kongju National University, Kongju, Chungnam, 314-701, Republic of Korea.
Sun
Byung-Yun
BY
Faculty of Biological Sciences, Chonbuk National University, Chonju, 561-756, Republic of Korea.
D032461:Chromosomes, Plant; D018744:DNA, Plant / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D004171:Diploidy; D019143:Evolution, Molecular; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D010802:Phylogeny; D011123:Polyploidy; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D029626:Ranunculaceae / Q000145:classification / Q000235:genetics*
D018744:DNA, Plant; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D012341:RNA, Ribosomal, 5S