ALLOZYME VARIATION AND PHYLOGENETIC-RELATIONSHIPS OF ASIAN, NORTH-AMERICAN, AND EUROPEAN POPULATIONS OF THE THREESPINE STICKLEBACK, GASTEROSTEUS-ACULEATUS

Allozyme variation was examined electrophoretically in the circumboreal threespine stickleback, Gasterosteus aculeatus, from 16 locations: Japan (6), western North America (4), eastern North America (2), and Europe (4). Thirteen of 18 loci were polyallelic among the samples, and statistical analyses demonstrated significant interpopulation divergence. Phylogenetic analyses of the relationships of the populations, employing Gasterosteus wheatlandi as the outgroup, recognized two primary clades: (1) European, North American, and some Japanese samples, which could be divided into an Atlantic basin clade comprised of the eastern North American and European populations, and a basal Pacific basin assemblage comprised of western North American and some Japanese Populations; and (2) a divergent group of Japanese populations. The larger assemblage of Pacific and Atlantic basin populations together comprise G. aculeatus. The divergent Japanese clade deserves further study and possible taxonomic recognition.