Rawson P D, Macnamee R, Frick M G, Williams K L
School of Marine Sciences, 5751 Murray Hall, University of Maine, Orono, ME 04469, USA.
Mol Ecol. 2003 Oct;12(10):2697-706. doi: 10.1046/j.1365-294x.2003.01940.x.
The barnacle, Chelonibia testudinaria, is a common inhabitant of the marine turtle epibiont community and plays a key role in the development of this community. Phylogeographic analysis of 79 cytochrome c oxidase I (COX1) sequences for barnacles collected from five populations found contrasting patterns of divergence for populations in the Atlantic vs. the Pacific Ocean. Our analysis indicates that the two Pacific populations, Senri Beach, Japan and Bahia Magdalena, Mexico, were not only highly divergent from the Atlantic populations but are highly divergent from one another. We suggest that barnacles from these populations may represent cryptic species. In contrast, sequence divergence was greatly reduced among barnacles collected from Wassaw Island, GA, USA, Keewaydin, FL, USA, and Kyparissia, Pèloponnésus Island, Greece. A reduction in sequence diversity at the latter site was attributed to a recent range expansion into the Mediterranean Sea. We examined historical patterns of migration among the three Atlantic and Mediterranean populations using the program migrate. This analysis indicates a high rate of migration from Keewaydin to Wassaw Island, contrasted with a much lower rate of migration in the opposite direction. The estimated migration rate from Kyparissia to Keewaydin was also non-negligible. We suggest that the association between C. testudinaria and loggerhead turtles and the patterns of turtle migration have played key roles in the expansion of the range of C. testudinaria into the Mediterranean Sea and the subsequent patterns of barnacle migration. We further propose that the difference between ocean basins, with respect to the impact of host migration on barnacle gene flow, probably stems from the fact that host-mediated dispersal in the Atlantic depends on advanced stage juveniles and adults while any host-mediated dispersal in the Pacific would have to involve early "pelagic" stage juvenile loggerheads.
龟甲藤壶（Chelonibia testudinaria）是海龟体表共生生物群落中的常见成员，在该群落的发展中起着关键作用。对从五个种群收集的79个藤壶细胞色素c氧化酶I（COX1）序列进行的系统地理学分析发现，大西洋种群与太平洋种群的分化模式形成对比。我们的分析表明，两个太平洋种群，即日本的千里海滩和墨西哥的马格达莱纳湾，不仅与大西洋种群高度分化，而且彼此之间也高度分化。我们认为，来自这些种群的藤壶可能代表隐存种。相比之下，从美国佐治亚州的瓦索岛、美国佛罗里达州的基韦丁岛和希腊伯罗奔尼撒半岛的基帕里西亚采集的藤壶之间的序列差异大大降低。后者地点的序列多样性降低归因于最近向地中海的范围扩张。我们使用migrate程序研究了三个大西洋和地中海种群之间的历史迁移模式。该分析表明，从基韦丁到瓦索岛的迁移率很高，而相反方向的迁移率则低得多。从基帕里西亚到基韦丁的估计迁移率也不可忽视。我们认为，龟甲藤壶与蠵龟之间的关联以及海龟的迁移模式在龟甲藤壶向地中海的范围扩张以及随后的藤壶迁移模式中发挥了关键作用。我们进一步提出，不同大洋盆地在宿主迁移对藤壶基因流动影响方面的差异，可能源于这样一个事实，即大西洋中宿主介导的扩散依赖于晚期幼体和成体，而太平洋中任何宿主介导的扩散都必须涉及早期“浮游”阶段的蠵龟幼体。
