Relaciones florísticas entre las comunidades relictuales del Norte Chico y la zona Central con el bosque del Sur de Chile

Abstract

Discontinuously distributed forests occurring along the coasts of central Chile and Norte Chico (northern Chile) present marked floristic affinities with the Valdivian rainforest of southern Chile. Those forests have been generally considered as relics of northward pleistocene extensions of the southern rainforest. In the present paper we determine the floristic similarity of forests from 11 localities between the IV and X Regions in Chile (30-40° S lat.), 4 of them from the north, 3 from the centre and 4 from the south. The similarity coefficients are correlated with geographic distances between sites. As expected, forests localized within each of the 3 geographic areas showed the highest floristic similarity (05A.77). The similarity values for northern and central forests were intermediate (035-0.54). Lower similarities were found be^ ween northern, central and southern localities. Notwithstanding the differences in geographic distances, northern and central forests present similar values of floristic relationship (0.07-0.28, N-S; 0.15-0.27. C-S) with the south. The various types of southern forest compared do not differ among themselves in their relation with northern and central ones. When comparing the floristic affinities of both central and northern localities with the southern rainforests, higher similarities were observed between the isolated island-like northernmost forests (Fray Jorge and Talinay) and the southernmost forests (Pérez Rosales). Likewise, Mocha island (Isla Mocha) showed a higher floristic similarity with the Perez Rosales forests tan with the nearestneighbor continental forest considered (Lebu). These results suggest that the northernmost and southernmost localities studied and Isla Mocha are floristically conservative. Our results do not support the hypothesis of a glacial or postglacial austral origin for the relict forests of the Norte Chico. Alternatively, the possible existence of a more ancient forest community, originally distributed throughout the 3 areas studied, is suggested.