Fauvelot C, Bernardi G, Planes S
Ecole Pratique des Hautes Etudes, ESA CNRS 8046, Université de Perpignan, F-66860 Perpignan Cedex, France.
Evolution. 2003 Jul;57(7):1571-83. doi: 10.1111/j.0014-3820.2003.tb00365.x.
This study investigated the influence of reproductive strategy (benthic or pelagic eggs) and habitat preferences (lagoon or outer slope) on both diversity and genetic differentiation using a set of populations of seven coral reef fish species over different geographic scales within French Polynesia. We hypothesized that a Holocene sea-level decrease contributed to severe reduction of population size for species inhabiting lagoons and a subsequent decrease of genetic diversity. Conversely, we proposed that species inhabiting stable environments, such as the outer slope, should demonstrate higher genetic diversity but also more structured populations because they have potentially reached a migration-genetic drift equilibrium. Sequences of the 5' end of the mitochondrial DNA (mtDNA) control region were compared among populations sampled in five isolated islands within two archipelagos of French Polynesia. For all the species, no significant divergences among populations were found. Significant differences in mtDNA diversity between lagoonal and outer-slope species were demonstrated both for haplotype diversity and sequence divergence but none were found between species with different egg types. Pairwise mismatch distributions suggested rapid population growth for all the seven species involved in this study, but they revealed different distributions, depending on the habitat preference of the species. Although several scenarios can explain the observed patterns, the hypothesis of population size reduction events relative to Holocene sea-level regression and its consequence on French Polynesia coral reefs is the most parsimonious. Outer-slope species have undergone a probable weak and/or old bottleneck (outer reefs persisted during low sea level, leading to reef area reductions), whereas lagoonal species suffered a strong and/or recent bottleneck since Holocene sea-level regression resulted in the drying out of all the atolls that are maximum 70 meters deep. Since present sea level was reached between 5000 and 6000 years ago, different demographic events (bottlenecks or founder events) have lead to the actual populations of lagoons in French Polynesia.
本研究利用法属波利尼西亚不同地理尺度下的七种珊瑚礁鱼类的一组种群，调查了繁殖策略（底栖卵或浮游卵）和栖息地偏好（泻湖或外坡）对多样性和遗传分化的影响。我们假设全新世海平面下降导致栖息在泻湖中的物种种群规模严重减少，进而导致遗传多样性降低。相反，我们提出栖息在稳定环境（如外坡）中的物种应表现出更高的遗传多样性，但种群结构也更明显，因为它们可能已达到迁移 - 遗传漂变平衡。对法属波利尼西亚两个群岛中五个孤立岛屿采样的种群，比较了线粒体DNA（mtDNA）控制区5'端的序列。对于所有物种，未发现种群间有显著差异。在单倍型多样性和序列分歧方面，泻湖物种和外坡物种的mtDNA多样性均显示出显著差异，但不同卵类型的物种之间未发现差异。成对错配分布表明本研究涉及的所有七种物种的种群均快速增长，但根据物种的栖息地偏好，它们呈现出不同的分布。尽管有几种情况可以解释观察到的模式，但相对于全新世海平面消退及其对法属波利尼西亚珊瑚礁的影响而言，种群规模减少事件的假设是最简洁的。外坡物种可能经历了一个可能较弱和/或较久以前的瓶颈期（外礁在低海平面时持续存在，导致礁区面积减少），而泻湖物种自全新世海平面消退导致所有最大深度为70米的环礁干涸以来，遭受了强烈和/或近期的瓶颈期。由于现今海平面在5000至6000年前达到，不同的人口统计学事件（瓶颈期或奠基者事件）导致了法属波利尼西亚泻湖目前的种群状况。
