Psephellus is a genus of flowering plants in the family Asteraceae (daisy family), placed in the tribe Cardueae — the thistle tribe that also includes knapweeds, cornflowers, and thistles. The genus is native to eastern Europe and western Asia, with its centre of diversity in the Caucasus region and adjacent Anatolia.
Plants in Psephellus are herbaceous perennials or annuals with alternate, often pinnatifid leaves and composite flower heads typical of the Cardueae: a cup-like involucre of bracts surrounds a disc of tubular florets, with the outermost florets sometimes enlarged and ray-like, giving the head a showy appearance similar to that of Centaurea. Flower colours range from violet-purple to pink and white.
The genus has a complex taxonomic history. Many species were formerly placed in Centaurea (the broad knapweed genus) and were transferred to Psephellus following molecular and morphological revisions that dismembered the old, broadly circumscribed Centaurea into several segregate genera. Psephellus is distinguished from Centaurea by a combination of involucre-bract and achene characters.
Taxonomy Notes
Psephellus was segregated from the large genus Centaurea (family Asteraceae, tribe Cardueae) following taxonomic revisions that used molecular data to resolve the polyphyletic Centaurea sensu lato. Many species formerly treated as Centaurea were transferred to Psephellus as a result. The genus is accepted by GBIF within Asterales.
Distribution
Psephellus is native to eastern Europe and western Asia, with the highest species diversity centred on the Caucasus mountains and adjacent parts of Turkey and Iran. Individual species in the genus extend to areas such as the Van region of eastern Turkey (P. vanensis), the Coruh valley, and the Abkhazia area of the southern Caucasus.
