Advances in chromosomal studies in Neottieae (Orchidaceae): constitutive heterochromatin, chromosomal rearrangements and speciation

In this work, we describe a karyomorphological study on three taxa of the tribe Neottieae (Orchidaceae). Epipactis aspromontana and E. schubertiorum are characterized by a chromosome complement of 2n = 2x = 38. Significant differences in heterochromatin distribution were found between them. Similarities in the karyotype structure and C-banding of E. schubertiorum and E. helleborine group have been observed. A specimen of E. aspromoniana showed a triploid chromosome number. The meiosis are characterized by univalent, bivalent and trivalent forms and in some somatic metaphase cells has been possible to observe a series of aneuploid numbers with 46, 47, 48, 49, 50, 51, 52 and 53 chromosomes. The largest differences can be emphasized between the Epipactis species and Neottia nidus-avis, mainly in the the karyomorphology and heterochromatin distributions. In Neottia nidus-avis the evolution process seems to be determined by reversing Robertsonian mutations.