Sources of invasions of a northeastern Pacific acorn barnacle, Balanus glandula, in Japan and Argentina

Within years of its introduction, the North American barnacle Balanus glandula Darwin, 1854 became an abundant member of rocky intertidal communities in Japan and Argentina. To determine the regional sources of these invasions, we compared mitochondrial cytochrome c oxidase subunit 1 (COI) and nuclear elongation factor 1 alpha (EF1) genotypes of native and introduced populations. Previously described population structure at these loci in North America conferred geographic information to genotypes. B. glandula from Argentina and southern to central California shared genotypes not found in other native populations. B. glandula from Japan and the northeastern Pacific (Puget Sound and Alaska) were differentiated from other populations by the presence of a nearly fixed nucleotide in EF1 and contained all 3 major haplotype groups of COI. These patterns indicate that sources of B, glandula in Japan and Argentina are largely from Alaska/Puget Sound and California, respectively. The broad similarity of mean seawater temperatures among introduced and native regions may have facilitated these invasions. The presence of greater variation in air temperatures in the invaded than native regions raises the possibility that temperature-related selection may play an important role in the evolution of these invasive populations. We found no evidence of multiple geographic sources of B, glandula in Japan and Argentina, nor of genetic bottlenecks in either invaded region.