DEVELOPMENTAL MODE AND SPECIES GEOGRAPHIC RANGE IN REGULAR SEA-URCHINS (ECHINODERMATA, ECHINOIDEA)

Among marine benthic organisms, the ability to disperse, primarily dur ing the larval stage, is widely thought to influence the extent of spe cies geographic range. Because related species often differ in their m odes of larval development (pelagic, feeding larvae; pelagic, nonfeedi ng larvae; or brooded development), and these can have dramatically di fferent planktonic intervals, the mode of development may influence ge ographic range. A global survey of 215 regular echinoids shows that sp ecies with pelagic, feeding larvae have significantly larger ranges th an those with pelagic, nonfeeding larvae, but there is no difference i n ranges between species with pelagic, nonfeeding larvae and those wit h brooded development. These patterns are maintained within the Cidaro ida and the Temnopleuroida, which account for the great majority of sp ecies with pelagic, nonfeeding development and brooded development. Th is limited effect of developmental mode on geographic range is found a mong species occurring predominantly in waters shallower than 100 m. F or species occurring deeper than 100 m. there is no significant differ ence in geographic range related to type of development. The relations hip between developmental mode and species range was examined more clo sely for circa 30 species for which the developmental period was known from laboratory observations. Adjusting the developmental times to a common temperature, 20 degrees C, using realistic values for Q(10) fro m 2.0 to 3.6, showed a highly significant, negative correlation betwee n egg volume and developmental time, indicating the potential for deve lopmental mode to influence the planktonic interval. However, there wa s no relationship between time in the plankton, estimated from unadjus ted developmental times, and extent of species geographic range. These results suggest that developmental mode may influence extent of speci es geographic ranges indirectly through the consequences of dispersal for gene how or recovery from disturbance.