Wood anatomy of the tribe Podalyrieae (Fabaceae, Papilionoideae): Diversity and evolutionary trends

Detailed wood anatomical data for 32 species from all nine genera of the tribe Podalyrieae are presented, together with numerical analyses and the mapping of character states onto the latest available molecular phylogeny. It was found that trees (Cadia, Calpurnia and Virgilia) have vessels in small isolated groups, whilst fynbos shrubs (the remaining genera: Amphithalea, Cyclopia, Liparia, Podalyria, Stirtonanthus and Xiphotheca) commonly show highly grouped narrow vessels (frequently in a dendritic pattern), and helical thickening on the vessel walls. Comparisons of the main character state changes with the molecular phylogeny of the tribe show that the wood structure of trees probably represents the basic condition in the tribe; character states present in shrubs appear to have arisen a few times and very likely represent adaptations to seasonal water stress. In general, the wood anatomy is congruent with current subtribal and generic delimitations. Fire-survival strategy is reflected in the rays, with seeders having mostly procumbent cells whilst sprouters have square and upright cells. The close similarity in wood anatomy between Cadia and Calpurnia is in agreement with the transfer of Cadia to the Podalyrieae. A remarkable diversity of crystals was found, including prismatic, acicular and navicular crystals, the last two of which may occur singly or in sheaf-like aggregates.