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The phylogenetic position of Pterocephalidium and the new African genus Pterothamnus within an improved classification of Dipsacaceae

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Abstract:

New data on fruit anatomy, floral characters and pollen morphology are reported for three species of Pterocephalus s.l. in its traditional circumscription: the annual W-Mediterranean Pterocephalus diandrus (now Pterocephalidium diandrum), the shrubby SE African P. centennii, and the E African P. frutescens. For comparison and augmentation of taxonomically relevant data, a few selected taxa of Cephalaria, Dipsacus, Knautia, Succisa, and Succisella were also studied. Important apomorphic differences between P. diandrus, P. centennii and the African P. frutescens as a typical representative of Pterocephalus s.str., support generic status for P. diandrus (as Pterocephalidium diandrum) and also strongly suggest separation of P. centennii from Pterocephalus s.str. as the new monotypic genus Pterothamnus, endemic to Africa (Mozambique). Pterocephalidium and Pterothamnus share several features (presence of floral bracts, 4-merous flowers, epicalyx anatomy, peculiar pollen morphology) and are placed into the new tribe Pterocephalidieae, which is clearly separated from Pterocephalus s.str. Available morphological, anatomical and palynological data support recent DNA-analytical evidence that Pterocephalidieae are related to the former tribes Dipsaceae (including Dipsacus, Cephalaria and possibly Simenia) and Knautieae (only Knautia), plus the new tribes Succiseae (Succisa and Succisella) and Pseudoscabioseae (Pseudoscabiosa). These four tribes constitute the “Dipknautid clade” sensu Carlson & al. and are here united under subfamily Dipsacoideae. Phylogenetically, this is sister to but quite distinct from subfamily Scabiosoideae, which includes the tribes Scabioseae s.str. (Scabiosa s.str., Sixalix, Pterocephalus s.str.) and the new Lomelosieae (Lomelosia, Pycnocomon). The position of the relic E Asian genus Bassecoia (incl. Pterocephalodes) is uncertain. Whereas DNA evidence places it at the base of Dipsacaceae and sister to the rest of the family, morphological characters strongly demonstrate closer affinities to Pseudoscabioseae. As a compromise, Bassecoia is made a separate tribe Bassecoieae, sister to Pseudoscabioseae within Dipsacoideae. This improved classification of Dipsacaceae shows unequivocally that multiplied and plumose calyx teeth, formerly considered exclusive for Pterocephalus, constitute a homoplastic and taxonomically misleading character that has evolved at least six times independently in Dipsacaceae.

Keywords: DIPSACACEAE; DIPSACOIDEAE; EPICALYX; FRUIT STRUCTURE; POLLEN CHARACTERS; SCABIOSOIDEAE

Document Type: Research Article

Affiliations: 1: Department of Structural and Functional Botany, Faculty Centre of Biodiversity, Faculty of Life Sciences, University of Vienna, Rennweg 14, 1030 Wien, Austria;, Email: veronika.mayer@univie.ac.at 2: Department of Systematic and Evolutionary Botany, Faculty Centre of Biodiversity, Faculty of Life Sciences, University of Vienna, Rennweg 14, 1030 Wien, Austria

Publication date: 2013-02-20

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