POSTGLACIAL RECOLONIZATION AND THE BIOGEOGRAPHY OF PALMARIA-MOLLIS (RHODOPHYTA) ALONG THE NORTHEAST PACIFIC COAST

We used random amplified polymorphic DNA (RAPD) markers to examine the distribution of genotypes of Palmaria mollis (Setchell et Gardner) va n der Meer et Bird, a red alga. We sampled populations along the North east Pacific coast from northern Washington to southwestern Alaska, an area extensively glaciated during the last ice age. Our objective was to determine whether the tracks of postglacial recolonization could b e extracted from the extant pattern of genotype distribution in a spec ies with limited dispersal capabilities. Thirty-eight individuals from 14 sites were sampled for RAPD markers using nine different random pr imers. As expected, individuals from the same population were more clo sely related to each other than to individuals from other populations. Relationships among populations, however, did not necessarily reflect geographic proximity. Rather, populations fell into groups correspond ing approximately to outer and inner coastal sites: the northwestern e nd of Vancouver Island and the Queen Charlotte Islands formed one oute r coast group, which associated with sites from Prince William Sound, the Alaska Peninsula, and Sitka, Alaska; the eastern side of Vancouver Island and Ketchikan, Alaska, represented one group of inner sites, w hich associated with sites near Juneau, Alaska and the eastern end of the Strait of Juan de Fuca. We conclude that this pattern does not rep resent a single postglacial recolonization event.