Malpighiales

Euphorbia polychroma. Photo: W. Stuppy.

Euphorbia polychroma. Photo: W. Stuppy.

The Malpighiales Science Team at RBG Kew was formed in 2001 in response to new insights in angiosperm systematics based on DNA sequence analysis. Its team members are based in the Herbarium, in the Molecular Systematics, Genetics, Micromorphology and Biological Interactions Sections of the Jodrell Laboratory and in the Seed Conservation Department. The main objective of Malpighiales research at RBG Kew is further resolution of relationships of major clades using molecular and non-molecular characters. This research aims to refine the present phylogenetic hypothesis of the clades and classification of the taxa comprising this order, some of which are still of doubtful rank and affinity. The novel concept of the order Malpighiales is now well-established in the botanical community, not least through publications and contributions to conferences by Kew staff. In the last five years, detailed molecular phylogenetic studies of all major segregate families of Euphorbiaceae sensu lato and the former Flacourtiaceae have been co-authored by members of the Kew Malpighiales Team. Phylogenetic analyses of some of the largest angiosperm genera, Euphorbia sensu lato and Phyllanthus sensu lato, have also been published with Kew participation. The study of character evolution made possible by a phylogenetic classification in a group where morphological characters are not openly indicative of phylogenetic relationships will provide particularly valuable insights into evolutionary mechanisms. An international development with large potential implications for Malpighiales systematics research is the generation of a near-complete genome sequence for a Populus species (www.ornl.gov/sci/ipgc/). Ongoing projects in the Genetics Section of the Jodrell Laboratory utilise genetic markers and expressed sequence tags (ESTs) generated by this consortium for population genomic studies of hybrid zones in the European species P. alba and P. tremula. These projects address the genetic make-up of the species barrier among these European taxa, and they are also expected to yield information about genetic markers or sequence regions for use in other related members of the Malpighiales.

In addition to molecular and anatomical-ontogenetic work, more baseline plant diversity research (taxonomic revisions and Flora accounts) is still urgently needed. Two new genera will be described in 2006 in Euphorbiaceae sensu lato alone, with a third to follow. Kew contributions have been made or are in progress to the Catalogue of Vascular Plants of the Southern Cone, Flore de Madagascar, Flora of China, Flora Malesiana and Flora of Thailand, and family overviews in reference works such as Kubitzki’s Families and Genera of Vascular Plants and the Natural History of Madagascar have been presented. A milestone in improving taxonomic expertise and accessibility of morphological data was the Interactive Key to the genera of Euphorbiaceae sensu lato which is now available at the Kew website. More Malpighiales families are being added such as Achariaceae sensu lato, Salicaceae sensu lato and Ochnaceae. Representation of taxa in Kew collections (mainly herbarium and DNA collections), especially in Euphorbiaceae sensu lato and Achariaceae/Salicaceae sensu lato, is strongest in continental Africa, SE Asia, the Indian subcontinent and South America. It has been further increased through fieldwork by Kew staff and targeted exchange with other institutions although certain geographic areas such as Indochina, Madagascar, New Caledonia and parts of Central America and the Caribbean remain under-represented. International interest in the order has increased over the last five years, particularly at the Smithsonian Institution and Harvard University Herbaria, and has been further boosted by the discovery that holoparasitic Rafflesiaceae are members of Malpighiales.