Systematics and Evolution of Pandanales

Character evolution in the monocot order Pandanales (five families), encompassing several anomalous morphological structures.

Sciaphila major (Triuridaceae), SEM female floral unit in axil of scale leaf

The circumscription of the monocot order Pandanales changed dramatically in the molecular phylogenetic era to include a novel association of five relatively species-poor families, Cyclanthaceae, Pandanaceae, Stemonaceae, Triuridaceae and Velloziaceae. The order encompasses a broad range of different habits – from large arborescent species of Pandanus, through climbers such as Stemona, to the inconspicuous achlorophyllous mycoheterotrophic Triuridaceae. It also includes many morphological structures that appear highly anomalous with respect to more “typical” monocots.

This project investigates the evolutionary history of the highly unusual morphological structures in the order. 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, though recent research supports a flower interpretation (Rudall & Bateman 2006; Rudall 2008).

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. We also employ novel techniques such as X-ray tomography (in collaboration with other researchers) to evaluate fossils in this group (Smith et al. 2008). This is a long-term project that is based in the Jodrell Laboratory and involves international collaborations, especially with the US-based project Assembling the Monocot Tree of Life (MonAToL). Research output is approximately one publication per year.