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

The diversity of marine macroinvertebrates has received increasing attentio n, although with little emphasis on its biogeographical significance. The p resent study analyses an updated data base on 1,601 littoral benthic specie s, belonging to: Demospongiae, Anthozoa, Polychaeta, Mollusca, Crustacea, E chinodermata y Ascideacea, whose records grouped into 10 zones, have been s tudied from the zoogeographic perspective. The groups best represented alon g the Chilean coast include the Mollusca (611 species), Polychaeta (403) an d the Crustacea (370), with an important influence on its general pattern o f biodiversity. This biodiversity showed a mild but progressive increase al ong the latitudinal gradient li om north to south, interrupted by maxima wh ich appear to reflect differences in study effort rather than normal behavi or. The degree of relationship between zones showed three faunistic units r ecently defined by Lancellotti % Vasquez. This arrangement, which was evide nt 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 ne ar 41 degrees S, as broadly suggested in the literature, was only seen in d ata for the Echinodermata and the Demospongiae other taxa show the existenc e of a region of transitional character having gradual replacement of speci es. Within the Regions, the biodiversity showed great homogeneity, contrary to endemism, which leached 52% in the Cold Temperate Region, as a conseque nce of an important number of single species records (38.2% species recorde d in only one zone). This represents the present lack of knowledge of the C hilean fauna, probably overestimating regional endemism, and thus distortin g knowledge of local patterns of biodiversity.