Karyomorphology and Evolution in Italian Populations of Three Neottieae Species (Orchidaceae)

A karyological analysis on Italian populations of 3 species, belonging to the genera Cephalanthera and Listera (Orchidaceae : Neottieae tribe) and characterized by asymmetrical karyotypes, was undertaken. Karyomorphological and C-banding data strongly suggest that in 2 species, namely C. damasonium and L. cordata, chromosomal rearrangements involving the large and medium-large chromosomes constituted the principal mechanism of chromosome evolution. This processis particularly evident in L. cordata, where karyotype evolution occurred by means of centric fission along with an increase in chromosome number and in the overall chromosomal heterochromatin content. Altogether the present observation on Italian specimens of the Neottieae corroborate previous proposals of a central role of Robertsonian rearrangements and quantitative heterochromatin varia-tion in karyotype reorganization.