Pollen of the Cercideae
The Cercideae is basally branching in the Leguminosae, and is a highly varied and complex group which has undergone many taxonomic re-organisations and contains many unresolved relationships. The pollen is correspondingly varied and complex, and is being studied to add characters to broader systematic studies as well as to understand pollination systems, ecology and evolution.
The pollen of the Cercideae has long been known to be diverse and variable. However, an unresolved species and genus level taxonomy has previously hindered understanding the complexity of the similarities and differences between various pollen structures. Recent studies suggest that a narrower circumscription of the genus Bauhinia is required, with the reinstatement of at least seven other genera which, until recently, were included in Bauhinia sensu lato (comprising around 350 species). In a recent molecular phylogenetic study, Brenierea forms a clade with the genera Piliostigma and Bauhinia sensu stricto. The remaining genera (Gigasiphon, Tylosema, Barklya, Phanera, Lasiobema and Lysiphyllum) form a second clade sister to the first.
Kew has a long history of studying pollen in collaboration with legume systematists, both within the RBG Kew legume team and world-wide, and in 2011 the focus of legume pollen studies turned to the monophyletic Cercideae to assist and complement other systematic and taxonomic work that was either in progress or planned. Thus, in addition to palynological data, characters from wood structure, floral development, biochemistry, macromorphology and DNA sequences will be included to further resolve relationships in this group. The pollen studies will firstly focus on the micro-structure of apertures, wall structure and ornamentation, which preliminary studies have revealed to be highly variable and important indicators of taxonomic and evolutionary significance.
Project Partners and Collaborators
Anne Bruneau, Carole Sinou (University of Montreal)