XVI International Botanical Congess

For most of this century, discrimination of higher taxa in the Phaeophyceae was based on thallus construction and life history pattern. These characters were broad in concept and did not always allow precise and unambiguous grouping of species. They were used for discriminating so-called lower and advanced orders, and for inferring phylogenetic relationships. Circumscription of orders and ideas on phylogeny became more refined with improved knowledge of the biology of brown algae, in particular as a result of detailed studies of life histories, reproduction and cell ultrastructure. At the same time, the status of some orders remained controversial, most notably within the group known as the Ectocarpales sensu lato. Gene-sequencing techniques provide new and powerful evidence that allows us to identify taxonomic characters that most accurately reflect phylogenetic relationships.