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

Autor(en)

Veronika Mayer, Friedrich Ehrendorfer

Abstrakt

The single-seeded fruits of the Dipsacaceae are enclosed by four fused bracts forming an

epicalyx. A detailed study of the epicalyx morphology and anatomy of nearly all of the

approximately 30 species of Pterocephalus s.l., together with other floral, palynological and

karyological data, suggest only 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) east Africa (P. frutescens) and southeast

Asia (P. hookeri, P. bretschneideri and P. siamensis). The latter are separated as a new genus:

Pterocephalodes. Pterocephalus s.s. lacks floral bracts, has numerous feathery calyx bristles

and 5-merous corollas, and is apparently monophyletic. Its species demonstrate the gradual

development of a hyaline corona, a diaphragma and other specialized epicalyx structures.

These and other features allows the recognition of a relatively plesiomorphic, very widespread

and paraphyletic basal group of perennial species (epicalyx type I), two more

apomorphic perennial groups (epicalyx types II and III), and two most advanced groups

(epicalyx types IV and V) with one perennial and two annual species. Pterocephalodes has floral

bracts and 4-merous corollas, also appears to be monophyletic, 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 well as the origin of a feathery pappus and of a corona. Thus, all three

genera allow an insight into the evolutionary processes of fruit differentiation in the

Dipsacaceae family.

Organisation(en)

Journal

Botanical Journal of the Linnean Society

Band

132

Seiten

247-278

Anzahl der Seiten

ISSN

0024-4074

Publikationsdatum

2000

Peer-reviewed

ÖFOS 2012

106008 Botanik

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