About Dioscorea

Dioscorea is a monocotyledon.  This genus of, arguably, 600-800 species of climbing plants is found mostly in tropical regions of the Old and New Worlds.   Dioscorea contains species that are economically important tubers crops, some of which are cultivated, some collected wild.  Many species are of medicinal importance in traditional medicines, and some have been exploited as sources of diosgenin, a precursor to semisynthetic steroids.

The history and distribution of yams around the world may be intimately connected  with the historical movement of continents and migration of human beings.   A phylogenetic understanding of the genus would allow us to add to this knowledge of the history of domestication of edible yams.  One of the goals of this laboratory (in collaboration with other scientists across the world) is to arrive at such a phylogenetic framework for the genus.

Molecular phylogenetic analyses of monocotyledons place  Dioscorea (and other Dioscoreales sensu stricto) nested within the monocotyledons.  However, several morphological data sets place Dioscorea near the origin of monocotyledons.  This difference in results may arise, in part, from its 'dicot'-like vegetative form.
 

The broad-leaved, long-petiolate, net-veined leaves of Dioscorea raise fascinating questions such as

• Are these retained ancestral, reversals, or re-inventions?
• Can developmental studies provide clues to the origin of this 'dicot'-like morphology?
•  early development
•  late development
• Does the development of complex leaves in Dioscorea resemble that of other monocots (Arisaema, palms)?
• Does it resemble complex leaf development in 'dicots'?

Species Relationships (PCR amplification, sequencing, phylogenetic analyses):

Chloroplast DNA sequences (ndhF gene and trnT-L, atpB-rbcL spacers)
Mitochondrial DNA sequences (nad 4)

Leaf Structure (Light and Scanning Electron Microscopy, Morphometric Analyses):

Early development and vascularization
Variation in leaf shape and venation
Heteroblastic variation in leaf form and vein density

 Leaf Function (being developed):

Water transport
Biomechanics