Systematics of Dioscoreales

Kew has played a key role in the discovery of novel information on the relationships of the yams and their allies and discovering new taxa. The information has been used to underpin conservation in a vitally important edible and medicinal plant group.

Female plant of Dioscorea birmanica Prain & Burkill from Thailand

Dioscoreales are one of the most critical taxa in monocot systematics, but have historically received much less attention than Asparagales or Liliales. The first goal of this project at its outset was to delimit the order and discover its higher level relationships. Having achieved this, subsequent research has focused on the yam genus Dioscorea, which is by far the most species-rich and economically important genus in the order. At least 50 species forming a wild-domesticated continuum are a vital starch source for millions in the tropics. The first (and to date only) phylogenetic systematic study of the genus was published by Kew in 2005; a dated phylogeny including additional taxa and sequence data from further DNA regions is in final preparation with collaborators (September 2011). Comparative studies are underpinned and facilitated by baseline plant diversity research, especially in Thailand and Madagascar, and by the discovery of new taxa in Dioscoreaceae and Burmanniaceae.

The data generated on yam diversity plays a critical role in identifying threatened taxa and links the project to conservation outcomes for taxa such as the recently described critically endangered species Dioscorea strydomiana.

A total of 13 papers on Dioscoreales have been published in peer-reviewed journals since 2006. Future phylogenetic research will be orientated towards extensively sampled species-level studies of the main clades of Dioscorea, initially in South Africa, Madagascar and Brazil.