Phylogenetic relationships in the tribe Alysseae (Brassicaceae) based on nuclear ribosomal ITS DNA sequences

Abstract

Sequence data from the nuclear ribosomal internal transcribed spacer (ITS) region of 85 species (131 accessions) were used to determine the tribal limits, monophyly status, and phylogenetic intra-tribal relationships of genera within the tribe Alysseae (Brassicaceae). Both maximum parsimony and maximum likelihood analyses support the recognition of the tribe Alysseae s. str. (12 genera: Alyssoides , Alyssum , Aurinia , Berteroa , Bornmuellera , Clastopus , Clypeola , Degenia , Fibigia , Galitzkya , Hormathophylla , and Physoptychis ). Six well-supported clades were recognized within the Alysseae clade, including two Alyssum clades (one of which includes Clypeola ), an Alyssoides and allies clade (includes Alyssoides , Bornmuellera , Clastopus , Degenia , Fibigia , Hormathophylla , and Physoptychis ), a Berteroa and allies clade (includes Aurinia , Berteroa , and Galitzkya ), a Bornmuellera clade, and a Hormathophylla clade. Morphological and cytological support for these clades is reviewed. The ITS data support the exclusion of the following taxa from the Alysseae, with appropriate tribal assignment given in parentheses: Alyssum klimesii Al-Shehbaz (Camelineae), Asperuginoides (unresolved), Athysanus (Arabideae), Botschantzevia (Arabideae), Didymophysa (unresolved), Farsetia (Malcolmieae), Lobularia (Malcolmieae), and Ptilotrichum (Arabideae). Farsetia and Lobularia are inferred to be monophyletic, and based on molecular and morphological characters they are assigned to Malcolmieae, a recently described tribe.