Jang Sook-Jin, Park Eunji, Lee Won-Kyung, Johnson Shannon B, Vrijenhoek Robert C, Won Yong-Jin
Interdisciplinary Program of EcoCreative, The Graduate School, Ewha Womans University, Seoul, South Korea.
Division of Ecoscience, Ewha Womans University, Seoul, South Korea.
BMC Evol Biol. 2016 Oct 28;16(1):235. doi: 10.1186/s12862-016-0807-9.
The Equator and Easter Microplate regions of the eastern Pacific Ocean exhibit geomorphological and hydrological features that create barriers to dispersal for a number of animals associated with deep-sea hydrothermal vent habitats. This study examined effects of these boundaries on geographical subdivision of the vent polychaete Alvinella pompejana. DNA sequences from one mitochondrial and eleven nuclear genes were examined in samples collected from ten vent localities that comprise the species' known range from 23°N latitude on the East Pacific Rise to 38°S latitude on the Pacific Antarctic Ridge.
Multi-locus genotypes inferred from these sequences clustered the individual worms into three metapopulation segments - the northern East Pacific Rise (NEPR), southern East Pacific Rise (SEPR), and northeastern Pacific Antarctic Ridge (PAR) - separated by the Equator and Easter Microplate boundaries. Genetic diversity estimators were negatively correlated with tectonic spreading rates. Application of the isolation-with-migration (IMa2) model provided information about divergence times and demographic parameters. The PAR and NEPR metapopulation segments were estimated to have split roughly 4.20 million years ago (Mya) (2.42-33.42 Mya, 95 % highest posterior density, (HPD)), followed by splitting of the SEPR and NEPR segments about 0.79 Mya (0.07-6.67 Mya, 95 % HPD). Estimates of gene flow between the neighboring regions were mostly low (2 Nm < 1). Estimates of effective population size decreased with southern latitudes: NEPR > SEPR > PAR.
Highly effective dispersal capabilities allow A. pompejana to overcome the temporal instability and intermittent distribution of active hydrothermal vents in the eastern Pacific Ocean. Consequently, the species exhibits very high levels of genetic diversity compared with many co-distributed vent annelids and mollusks. Nonetheless, its levels of genetic diversity in partially isolated populations are inversely correlated with tectonic spreading rates. As for many other vent taxa, this pioneering colonizer is similarly affected by local rates of habitat turnover and by major dispersal filters associated with the Equator and the Easter Microplate region.
东太平洋的赤道和复活节微板块区域呈现出地貌和水文特征，这些特征对许多与深海热液喷口栖息地相关的动物构成了扩散障碍。本研究考察了这些边界对喷口多毛纲动物庞贝蠕虫（Alvinella pompejana）地理细分的影响。在从十个喷口地点采集的样本中，检测了来自一个线粒体基因和十一个核基因的DNA序列，这些地点涵盖了该物种已知的分布范围，从东太平洋海隆北纬23°到太平洋南极海岭南纬38°。
从这些序列推断出的多位点基因型将个体蠕虫聚类为三个复合种群片段——东太平洋海隆北部（NEPR）、东太平洋海隆南部（SEPR）和东北太平洋南极海岭（PAR）——被赤道和复活节微板块边界分隔开。遗传多样性估计值与构造扩张速率呈负相关。迁移隔离（IMa2）模型的应用提供了关于分歧时间和种群统计学参数的信息。估计PAR和NEPR复合种群片段大约在420万年前（Mya）（242 - 3342万年前，95%最高后验密度，（HPD））分裂，随后SEPR和NEPR片段在约79万年前（007 - 667万年前，95% HPD）分裂。相邻区域之间的基因流估计大多较低（2Nm < 1）。有效种群大小的估计值随纬度降低：NEPR > SEPR > PAR。
高效的扩散能力使庞贝蠕虫能够克服东太平洋活跃热液喷口的时间不稳定性和间歇性分布。因此，与许多同域分布的喷口环节动物和软体动物相比，该物种表现出非常高的遗传多样性水平。尽管如此，其在部分隔离种群中的遗传多样性水平与构造扩张速率呈负相关。与许多其他喷口类群一样，这种先锋殖民者同样受到当地栖息地更替速率以及与赤道和复活节微板块区域相关的主要扩散过滤因素的影响。
