A critique of traditional approaches to seaweed distribution in light of the development of vicariance biogeography
An overview of the primary approaches to seaweed biogeography is provided in light of the development of vicariance biogeography. Each approach is discussed with particular regard to the extent to which the methods and objectives are compatible with vicariance. Ecological biogeography is considered an offshoot of ecology and physiology and is more appropriate in determining current distributions of organisms and aspects of physiological ecology rather than the speciation history of monophyletic groups. The R/P quotient of Feldmann and distribution of algal life-forms do not fall within the aegis of vicariance and are considered useful only in a descriptive sense. The examination of seaweed spans propounded by Pielou is considered flawed because of the lack of dependence on monophyletic groups. The floristic school of analysis of many seaweed biogeographers is analagous to the panbiogeography of Croizat, and provides the basis for the more concrete phylogenetic hypotheses that are the basis for vicariance analysis. The latter is considered the best methodology for studying the relationship between patterns of cladogenesis and the distribution of constituent taxa.
Geographical variation in the distributions of macroalgae in estuaries
Assemblages of macroalgal species present in the upper reaches of estuaries were compared using published species lists for the North Atlantic, covering a north-south gradient in Europe from Iceland to northern Spain, and in North America between the St. Lawrence and Virginia. Patterns were sought using cluster analysis and ordination. Three groupings of estuaries were noted: Icelandic, mainland European and American. There was a slight trend of increase in the ratio of red to brown algae with decreasing latitude in Europe, though not as marked as for open coastal algae. This might be associated with the effect of temperature on salinity tolerance. Despite this biogeographic trend, some of the commonest species appear to be widely spread through estuaries, possibly including southern Atlantic and Pacific locations. Confirmation of the trends suggested requires further data from southern European estuaries.
Kelps as Fouling Organisms on North Sea Platforms
As a result of laboratory experiments and studies of the life cycle with both light and electron microscopy, it is suggested that the most likely stages of dispersal from coastal populations to the platforms are the filamentous gametophytes and young sporophytes. While still at the microscopic phase the sporophyte develops rhizoids, which are cells specially modified for adhesion. The structure of these cells and the development of the basal attaching organ is outlined.