Viburnales: cytological features and a new circumscription

Cytological studies carried out in 98 species (22 genera out of eight famil ies: Caprifolicaea, Sambucaceae, Viburnaceae, Adoxacene, Dipsacaceae, Morin aceae and Cayceraceae) of the Dipsacales s.l. and the eventually related fa milies Cornaeae, and Hydrangeaceae point to a very close relationship betwe en the Viburnaceae, Sambucaceae and Adoxaceae, corroborating the inclusion of these families into an order different from the Dipsacales, namely the V iburnales. Many cytological features shared by these families differ strong ly from the Dipsacales s.str., especially(1) chromosome size and morphology , (2) the presence of cold induced chromosome regions:(CIRs), (3) interphas e nuclear structure, and (4) chromosome condensing behaviour at prophase. C ornaceae and Hydrangeaceae present similar interphase nuclei, but differ fr om the Viburnales by other karyomorphological characters. The results are d iscussed with respect to previous morphological, embryological, and molecul ar findings.