Patterns and breaking points in the distribution of benthic algae along the temperate Pacific coast of South America

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 4º and 56ºS 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 6ºS, from 6 to 30ºS and from 30 to 55ºS. Since 1980, new information on marine algae along this coastline allows a 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 4º to 56ºS 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 are 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 12º and 42ºS. Another two breaking points occur at 20ºS and at 33ºS in Phaeophyta and Rhodophyta species composition respectively. The inclusion of single-record species does not affect significantly the distribution of species along this coastline