Cytotaxonomical study ofSaxifraga seriesCeratophyllae s.l. (Saxifragaceae)

Chromosome numbers, mainly gametic, are given for 28 populations belonging to 13 species in ser.Ceratophyllae as circumscribed byWebb & Gornall. From a cytological point of view, we report or confirm the occurrence of aneuploidy in at least 8 of the 19 species recognized. This phenomenon, together with the technical difficulties inherent to the genus, is responsible for a number of incorrect or imprecise previous reports which are here questioned. Aneuploidy and the karyological instability behind it apparently reflect very active extant processes which might play an important role in the evolution of the group. Cytological and morphological data allow the recognition of four groups; one of them is likely to constitute a monophylectic group (ser.Ceratophyllae sensu stricto) but, the monophyly of the seriesCeratophyllae sensu lato is questioned.