Zoogeography of benthic macroinvertebrates of the Chilean coast: contribution for marine conservation

The diversity of marine macroinvertebrates has received increasing attention, although with little emphasis on its biogeographical significance. The present study analyses an updated data base on 1,601 littoral benthic species, belonging to: Demospongiae, Anthozoa, Polychaeta, Mollusca, Crustacea, Echinodermata y Ascideacea, whose records grouped into 10 zones, have been studied from the zoogeographic perspective. The groups best represented along the Chilean coast include the Mollusca (611 species), Polychaeta (403) and the Crustacea (370), with an important influence on its general pattern of biodiversity. This biodiversity showed a mild but progressive increase along the latitudinal gradient li om north to south, interrupted by maxima which appear to reflect differences in study effort rather than normal behavior. The degree of relationship between zones showed three faunistic units recently defined by Lancellotti % Vasquez. This arrangement, which was evident in the most diverse groups, became altered in the lesser speciose groups where differences obeyed a pattern of affinity to particular zones within the Transitional Temperate Region. The presence of a zoogeographic break near 41 degrees S, as broadly suggested in the literature, was only seen in data for the Echinodermata and the Demospongiae other taxa show the existence of a region of transitional character having gradual replacement of species. Within the Regions, the biodiversity showed great homogeneity, contrary to endemism, which leached 52% in the Cold Temperate Region, as a consequence of an important number of single species records (38.2% species recorded in only one zone). This represents the present lack of knowledge of the Chilean fauna, probably overestimating regional endemism, and thus distorting knowledge of local patterns of biodiversity.