DISTRIBUCIÓN BIOGEOGRÁFICA DE LOS MOLUSCOS HOLOCENOS DEL LITORAL ARGENTINO-URUGUAYO

Abstract

The biogeographie distribution of the Holoeene marine molluses from the Argentine-Uruguayan littoral was analyzed. Following the present-day denomination, two biogeographie regions were defined: the Argentina Province and the Magellan Province. The 197 species formed several faunal groups: species widely distributed within the region; species with intermediate range; and species restrieted to specific areas. With few exceptions, the Holoeene fauna consists of species living in the adjacent waters. The geographic persistenee of the species indicates, on the whole, similar climatic conditions during the Holocene. Nevertheless, minor temperature fluetuations produced slight displacements of the distribution range of some taxa. From an ecological viewpoint, the major differences between the two provinces are the increase of (he epifauna in the Magellan Province and a higher proportion of burrowing speeies in the Argentina Province, in accordance with the predominance of rocky or sandy substrata, respectively.