World-wide latitudinal and longitudinal seaweed distribution patterns and their possible causes, as illustrated by the distribution of Rhodophytan genera

• Published in: Helgoländer Meeresuntersuchungen
• Main Author: van den Hoek, C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 1984
• Subjects: Antarctic; Arctic; New Zealand; Pacific; The Antarctic; Antarc*
• Online Access: https://hdl.handle.net/11370/6202a760-9e8e-44e4-a07d-825c6f03c7cb; https://research.rug.nl/en/publications/6202a760-9e8e-44e4-a07d-825c6f03c7cb; https://doi.org/10.1007/BF01997483

The degree of similarity between red algal generic floras in each pair of 22 climatically defined biogeographic regions was established on a world-wide scale by Jaccard's similarity index and by an hierarchical clustering with an agglomerative centroid method. Two clusterings were carried out, the first one on the basis of all 637 genera, and the second one on the basis of genera not occurring in the tropics and non-endemic to any one of the 22 regioms (145 genera). This latter clustering served to detect better the relationships among non-tropical floras. The results indicate the following division of the earth's rhodophytan seaweed floras: (1) A rich tropical-warm temperate "Tethyan" group including the rich tropical Indo W Pacific and W Atlantic floras, and the rich warm temperate NW Pacific and NE Atlantic floras; (2) the depauperate extensions of the above group (the tropical E Pacific and E Atlantic floras, and the warm temperate NW and SW Atlantic floras); (3) a cold temperate and a warm temperate N Pacific group; (4) an Arctic-cold temperate N Atlantic group and a NE Atlantic warm temperate flora; (5) an Antarctic-cold temperate southern hemisphere group including the cold temperate SE Pacific, SW Atlantic, SE Atlantic floras, and the Antarctic flora; (6) the two highly individual, but slightly related warm temperate SE Atlantic flora (S. Africa) and SW Pacific flora (Southern Australia and Northern New Zealand); (7) the depauperate warm temperate SE Pacific flora. Although the northern and southern hemisphere temperate and polar floras are quite unrelated (on the basis of genera lacking in the tropics), they share nonetheless a number of cool water genera which apparently have succeeded in passing the adverse tropical belt. The rich tropical-warm temperate group is thought to consist of vicariant portions of a formerly continuous Tethyan flora. The N Pacific and N Atlantic temperate floras are thought to have developed independently since the Oligocene (~ 40.106 y) deterioration of the climate and to ...