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 alg al species of the Pacific temperate coast of South America could be grouped into five components according to their geographic affinities. Each of the se components was distributed differentially along the coastline between 3 degrees and 56 degreesS and thus, their contribution to the overall flora v aried depending on the latitude. Species composition changed at specific la titudes in such a way that three groups could be observed: from 4 to 6 degr eesS, from 6 to 30 degreesS and from 30 to 55 degreesS. Since 1980, new inf ormation on marine algae along this coastline allows 3 review of the previo us phytogeographic characterization. The presence/absence of algal species, separated by division and geographic affinity, was recorded for each degre e of latitude from 4 degrees to 56 degreesS and used to analyze the similar ity in species composition and possible changes in distribution patterns. R esults show the same five geographic components detected 20 years ago with similar distributions. Differences observed an a further southward intrusio n of subtropical elements, a decrease in endemic species number and relativ e contribution to the flora at the southern tip of South America, and two b reaking points in species composition at 12 degrees and 42 degreesS. Anothe r two breaking points occur at 20 degreesS and at 33 degreesS in Phaeophyta and Rhodophyta species composition respectively. The inclusion of single-r ecord species does not affect significantly the distribution of species alo ng this coastline.