Fruit differentiation, palynology, and systematics in Pterocephalus Adanson and Pterocephalodes, gen. nov (Dipsacaceae)

The single-seeded fruits of the Dipsacaceae are enclosed by four fused brac ts forming an epicalyx. A detailed study of the epicalyx morphology and ana tomy of nearly all of the approximately 30 species of Pterocephalus s.l., t ogether with other floral, palynological and karyological data, suggest onl y loose relationships and convergent similarities (homoplasies) between the core of the taxa (Pterocephalus s.s.), ranging from south-west and central Asia (P. gedrosiacus, P. afghanicus) to Macaronesia (e.g. P. dumetorum) ea st Africa (P. frutescens) and south-east Asia (P. hookeri, P. bretschneider i and P. siamensis). The latter are separated as a new genus: Pterocephalod es. Pterocephalsus s.s. lacks floral bracts, has numerous feathery calyx br istles and 5-merous corollas, and is apparently monophyletic. Its species d emonstrate the gradual development of a hyaline corona, a diaphragma and ot her specialized epicalyx structures. These and other features allows the re cognition of a relatively plesiomorphic, very widespread and paraphyletic b asal group of perennial species (epicalyx type I), two more apomorphic pere nnial groups (epicalyx types II and III), and two most advanced groups (epi calyx types IV and V) with one perennial and two annual species. Pterocepha lodes has floral bracts and 4-merous corollas, also appears to be monophyle tic, and is limited to the eastern Himalaya and south-west China. It shares with Pseudoscabiosa the lack of a diaphragma in some of its species as wel l as the origin of a feathery pappus and of a corona. Thus, all three gener a allow an insight into the evolutionary processes of fruit differentiation in the Dipsacaceae family. (C) 2000 The Linnean Society of London.