Figure 1. Bipolar distribution of the temperate seaweed genus Palmaria (Rhodophyta) with its single endemic species (P. palmata) in the North Atlantic, and seven other species in the North Pacific and circumpolar southern oceans (arrow heads). More or less continuous distributions in northern hemisphere indicated with thickened coastlines. Additional scattered records in Arctic Ocean for P. palmata not indicated. This distribution is similar to the overall distribution of the Palmariaceae, which includes at least eight additional species in three other genera.

Figure 2. Summary of primary historical events (A, S, P) influencing tropical marine algal floristic regions: 1, Indo-West Pacific tropical region; 2, eastern Pacific tropical region; 3, western Atlantic tropical region; and 4, eastern Atlantic tropical region. In the Permian a continuous tropical flora existed in the Tethys Sea. In the Jurassic the rifting of the Atlantic Ocean (A) differentiated floras in the Old and New Worlds (OW and NW, respectively), with the African flora strongly influenced by the Western Atlantic. The land bridge at Suez (S) closed dispersal into the central Atlantic in the Miocene (19 million years ago) and the isthmus at Panama (P) closed dispersal in the New World in the Pliocene (4 million years ago). Note some dispersal from the tropical Indian Ocean to tropical West Africa and the Americas from the Cretaceous. Arrow heads show approximate northern and southern limits of tropical floras on relevant continental margins. Arrow size indicates relative importance of dispersal (modified from Lüning, 1990).

Figure 3. Distribution of the three species of Macrocystis: M. integrifolia (asterisks), M. angustifolia (arrows), M. pyrifera (arrow heads). Note amphiequatorial distribution and extensive range in southern hemisphere.