title: Electrophoretic karyotype polymorphism of sibling species of the Paramecium aurelia complex.
abstract: Variability of karyotypes is one of the main mechanisms of speciation in organisms. Electrophoretic karyotypes of the macronucleus (MAC) obtained by pulsed-field gel electrophoresis were compared for 86 strains of all 15 sibling species of the Paramecium aurelia complex in order to determine if karyotype differences corresponded to biological species boundaries. Because the electrophoretic karyotype of the MAC reflects indirectly the frequency and distribution of fragmentation sites in the micronuclear (MIC) chromosomes, any change in MAC electrophoretic karyotype may be a marker of certain chromosomal mutations in the MIC. Thirteen main variants of electrophoretic MAC karyotypes were observed in this species complex. Ten of them appeared to correspond to biological species, while the three other variants characterized several species each. Intraspecific polymorphism was observed for several species: in some cases a certain variant of MAC karyotype was specific for all strains from the same part of the world. Distribution of the MAC karyotype variants along molecular phylogenetic trees of the P. aurelia complex shows that isolation of each species or group of species of this complex was accompanied by divergence in the molecular organization of the genome.
authors.affiliation: Faculty of Biology and Soil Science, St. Petersburg State University, Saint Petersburg 199034, Russia.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Nekrasova
authors.forename: Ewa
authors.initials: E
authors.lastname: Przyboś
authors.forename: Maria S
authors.initials: MS
authors.lastname: Rautian
authors.forename: Alexey A
authors.initials: AA
authors.lastname: Potekhin
mesh_terms: D015139:Blotting, Southern; D002875:Chromosomes; D016172:DNA Fingerprinting; D016054:DNA, Protozoan / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D007621:Karyotyping / Q000379:methods; D048489:Paramecium aurelia / Q000145:classification / Q000166:cytology* / Q000235:genetics; D011110:Polymorphism, Genetic
chemical_list: D016054:DNA, Protozoan