GENETIC VARIATION WITHIN AND BETWEEN GEOGRAPHICALLY SEPARATED POPULATIONS OF THE SEA URCHIN, ARBACIA PUNCTULATA

¹ Biology Department, Yale University, New Haven, Connecticut 06520

Genotypic variation, inferred from isozyme differences in twelve enzyme systems, was measured by means of horizontal microacrylamide gel electrophoresis in four populations of the sea urchin, Arbacia punctulata, from the Atlantic coast of the United States. An additional population from the Gulf of Mexico was surveyed for four enzymes. Although gene frequencies were significantly different among Atlantic populations, the overall values of genetic distance were within the range observed for geographic populations of other species. A balance between migration and selection is proposed to account for the patterns of genetic variation. Striking differences in gene frequency were not observed when Atlantic coast populations were compared with Gulf of Mexico specimens.