RELATIONSHIP BETWEEN LARVAL TYPE AND GEOGRAPHIC RANGE IN MARINE SPECIES - COMPLEMENTARY OBSERVATIONS ON GASTROPODS

From a faunal list of 216 of the most common species of prosobranch gastropods at Beaufort, North Carolina, a group of 87 species was selected on the basis of known life cycles and geographic distributions. The larval types were categorized as teleplanic, actaeplanic, or nonplanktonic. The presence of these species in eight approximately equivalent latitudinal zones along the western shore of the Atlantic Ocean was then recorded (Scheltema, 1989). This list has been used, in the present paper, in three different ways: to identify homogeneity or heterogeneity of spatial distribution of the three biological groups; to record the presence of species in geographic sectors defined on the basis of average annual sea surface temperature; and to compare, at the two extremes of the region studied, the areas occupied by species having a particular type of development in common. It was found that: 1) the dominant type of development within a latitudinal zone depends on the geographic position of this zone; 2) the extent of the area of distribution of species with a given type of reproduction varies with latitude; 3) in terms of sea surface temperature limits, teleplanic and nonplanktonic species have similar patterns of distribution; 4) the distributions observed, whether along the coastline or transoceanic, are not fully accounted for by the inherent dispersal capacities related to larval type.