HESPEROCODON, A NEW GENERIC NAME FOR WAHLENBERGIA HEDERACEA (CAMPANULACEAE): PHYLOGENY AND CAPSULE DEHISCENCE

Abstract

The European species Wahlenbergia hederacea (L.) Rchb. (Campanulaceae) is molecularly distant from the remainder of the wahlenbergioids, and its inclusion with them renders the tribe Wahlenbergieae Endl. (1838) non-monophyletic. Additional support for this conclusion may be derived from its gross morphological characteristics, which are essentially campanuloid. However, although not strictly identical to that of Wahlenbergia Schrad. ex Roth, the capsule dehiscence mechanism of W. hederacea is still fundamentally wahlenbergioid and differs from the majority of campanuloids. Several genera such as Feeria and Jasione, which are intermediate between typical wahlenbergioids and typical campanuloids, have similar capsule characteristics, and it is postulated that Wahlenbergia hederacea, together with these ‘transitional’ genera, are all relatively ancient components of a campanulaceous palaeoflora of the early Tertiary of Eurasia. The wahlenbergioid type of dehiscence is considered to be a plesiomorphic character whereas the diverse campanuloid types of dehiscence mechanisms are derived under conditions of intense selection. It is suggested that Wahlenbergia hederacea is probably most closely related to, and ancestral to, the rapunculoid lineages of Campanula s.l. that subsequently evolved over much of Eurasia and North America. Consequently, Wahlenbergia hederacea should be classified in the Campanuloideae and the new generic name Hesperocodon Eddie & Cupido gen. nov. is proposed.