A reappraisal of Phyllolepidum (Brassicaceae), a neglected genus of the European flora, and its relationships in tribe Alysseae

Abstract

New light is shed on the evolutionary affinities and generic diversity in Alysseae (Brassicaceae) by means of nuclear DNA sequences. Internal transcribed spacer analysis was used to assess the relationships and the monophyletic status of Aurinia and Ptilotrichum, when defined to include three poorly known taxa from southeast Europe. The alpine Ptilotrichum rupestre from central Appennines and its Balkan and Anatolian relative Ptilotrichum cyclocarpum clustered together as sister to Bornmuellera and Leptoplax, while their evident lack of affinity with the Asian type species of Ptilotrichum (Arabideae) leads to the definitive exclusion of the latter from the European flora. To accommodate the two species mentioned above, the so far neglected genus Phyllolepidum is accepted. The rare pontic endemic Aurinia uechtritziana resulted closely related to Berteroa and Galitzkya and is treated here as the sole member of Lepidotrichum. Comparative scanning electron micrograph analyses of trichome morphology are consistent with the phylogenetic evidence. The new combinations Phyllolepidum cyclocarpum and P. cyclocarpum subsp. pindicum are proposed, and a key for the identification of all European genera of the Alysseae is presented.

Keywords:

• Aurinia
• Lepidotrichum
• molecular phylogeny
• Phyllolepidum
• Ptilotrichum
• trichome morphology

Acknowledgements

Fabio Conti (University of Camerino) provided fresh samples of P. rupestre for molecular analysis. Tiziana Gonnelli and Marta Mariotti (University of Florence) kindly gave technical support for SEM analyses. Chiara Nepi, curator of the Herbarium Centrale Italicum (FI) kindly allowed study of herbarium material. Special thanks to Federico Selvi (University of Florence) for his precious help in results, discussion and proof revision. The bulk of molecular data-set derives by the studies of Suzanne Warwick and co-workers. An anonymous reviewer provided useful comments and suggestions on the first version of the manuscript.