Nonea, one of the largest but lesser known genera of Boraginaceae tribe Boragineae, has been investigated by means of phenetics and cladistics to analyse morphological diversity and phylogenetic relationships within the group. Cluster analysis of 29 taxa recognizes five groups of annual species placed in one large cluster and two groups of perennial taxa in another cluster. Principal Component Analysis shows that the enigmatic Greek species, Paraskevia cesatiana (≡ Nonea cesatiana), is morphologically intermediate between Nonea and Pulmonaria, but closer to the latter due to fruit characters. Successive weighting using 42 characters and Pulmonaria as outgroup indicates that Nonea is paraphyletic, because the two species of Elizaldia are nested within the group of annual taxa. The South Mediterranean species N. vesicaria is closer to the North African taxa of Elizaldia than to any other member of Nonea. The perennial species of the N. intermedia group growing in mesic habitats of the Pontic-Caucasian region and Eastern Anatolia are in basal position, whereas Paraskevia cesatiana is not nested within Nonea. Candolle's sections of Nonea are not clearly supported. Nonea sect. Orthocaryum also appears paraphyletic due to the position of N. obtusifolia, a taxon with numerous autapomorphies that are difficult to interprete phylogenetically. Possible trends of character evolution are discussed also in the light of cytogeographical aspects. These aspects indicate x = 10 as the primary base number and either polyploidy or descending dysploidy associated with the adaptive shortening of the life-cycle as major driving forces of species formation.
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