Abstract

According to biogeographic studies made two decades ago, marine benthic algal species of the Pacific temperate coast of South America could be grouped into five components according to their geographic affinities. Each of these components was distributed differentially along the coastline between 3 degrees and 56 degreesS and thus, their contribution to the overall flora varied depending on the latitude. Species composition changed at specific latitudes in such a way that three groups could be observed: from 4 to 6 degreesS, from 6 to 30 degreesS and from 30 to 55 degreesS. Since 1980, new information on marine algae along this coastline allows 3 review of the previous phytogeographic characterization. The presence/absence of algal species, separated by division and geographic affinity, was recorded for each degree of latitude from 4 degrees to 56 degreesS and used to analyze the similarity in species composition and possible changes in distribution patterns. Results show the same five geographic components detected 20 years ago with similar distributions. Differences observed an a further southward intrusion of subtropical elements, a decrease in endemic species number and relative contribution to the flora at the southern tip of South America, and two breaking points in species composition at 12 degrees and 42 degreesS. Another two breaking points occur at 20 degreesS and at 33 degreesS in Phaeophyta and Rhodophyta species composition respectively. The inclusion of single-record species does not affect significantly the distribution of species along this coastline.