A CLADISTIC-ANALYSIS OF THE EVOLUTION AND BIOGEOGRAPHY OF DURVILLAEA (PHAEOPHYTA)

The genus Durvillaea currently has four recognized species found along many exposed, rocky coastlines of the temperate to sub-Antarctic regi ons in the Southern Hemisphere. We propose that the current species di stributions are related primarily to vicariance events and subsequent speciation associated with the breakup of Gondwana between 40 and 100 Ma. From an ancestral species, a stipitate species developed in the Ta sman basin, with separation and speciation resulting in the D. potator um/D. willana complex in southeastern Australia and New Zealand. A sec ond line of evolution led to D. chathamensis and D. antarctica charact erized by a honey-combed Medulla. The extensive distribution of D. ant arctica throughout the Southern Hemisphere is related to both vicarian ce and dispersal events. The status of D. chathamensis as a species di stinct from D. antarctica is questioned. The affinities of an as yet u ndescribed taxon from the Antipodes Islands are thought to be with the D. potatorum complex but require further study before they can be def ined more precisely.