Systematics and Evolution of Pandanales
Sciaphila major (Triuridaceae), SEM female floral unit in axil of scale leaf
The newly-recircumscribed monocot order Pandanales includes five families, Cyclanthaceae, Pandanaceae, Stemonaceae, Triuridaceae and Velloziaceae, each of which contains relatively few genera and species. They range in habit from large arborescent species of Pandanus, through climbers such as Stemona, to the inconspicuous achlorophyllous mycoheterotrophic Triuridaceae.
This novel association of families has prompted us to reassess the wide range of reproductive structures in the order, some of which appear highly anomalous with respect to more typical lilioid monocot flowers. For example, flowers of Triuridaceae possess multiple free carpels, and those of some Stemonaceae and Pandanaceae possess a single carpel; both conditions are unusual in monocots, and are derived in this group. Furthermore, dimerous and tetramerous flowers occur frequently within Pandanales, contrasting with the trimerous flowers that are common in other monocots. In some Pandanales even the identity of the flower is questionable, since the flower–inflorescence boundary is ambiguous. The notorious "inside-out" floral construction in the Mexican genus Lacandonia (Triuridaceae) has been interpreted as representing either a single flower, or as a pseudanthium derived from a group of highly reduced flowers.
Understanding the relationships and synapomorphies within the newly-circumscribed Pandanales is crucial to understanding the evolutionary history of their diverse floral characters. Analyses of molecular data have hitherto proved problematic because chloroplast DNA data are lacking for the mycoheterotrophic family Triuridaceae; thus we are utilising a combination of morphological and molecular data to provide a phylogenetic hypothesis that will form the basis for assessments of floral evolution.
Project Team
Project Leader: Rudall, Paula
Herbarium
William Baker, Martin Cheek, Paul Wilkin
Jodrell Laboratory
Carol Furness, Paula Rudall , Richard Bateman
Project Partners and Collaborators
Mexico
Francisco Vergara-Silva
UK
Natural History Museum