Maes Gregory E, Pujolar J M, Hellemans B, Volckaert Filip A M
Laboratory of Aquatic Ecology, Katholieke Universiteit Leuven, Ch. Deberiotstraat 32, B-3000 Leuven, Belgium.
Mol Ecol. 2006 Jul;15(8):2095-107. doi: 10.1111/j.1365-294X.2006.02925.x.
Life history traits of highly vagile marine species, such as adult reproductive success and larval dispersal, are strongly determined by oceanographic and climatic forces. Nevertheless, marine organisms may show restricted dispersal in time and space. Patterns of isolation by distance (IBD) have been repeatedly observed in marine species. If spawning time is a function of geographical location, temporal and spatial isolation, can easily be confounded or misinterpreted. In this study, we aimed at discriminating between various forces shaping the genetic composition of recruiting juveniles of the European eel (Anguilla anguilla L.). By controlling for geographical variation, we assessed temporal variation and tested for possible isolation by time (IBT) between recruitment waves within and between years. Using 12 polymorphic allozyme and six variable microsatellite loci, we show that genetic differentiation was low (F(ST) = 0.01-0.002) and significant between temporal samples. Regression analysis between genetic and temporal distance, was consistent with a subtle interannual pattern of IBT. Our data suggest that the population dynamics of the European eel may be governed by a double pattern of temporal variance in genetic composition: (i) a broad-scale IBT of spawning cohorts, possibly as a consequence of the large migration loop in anguillids and strong variance in annual adult reproductive contribution; and (ii) a smaller-scale variance in reproductive success (genetic patchiness) within cohorts among seasonally separated spawning groups, most likely originating from fluctuating oceanic and climatic forces. The consistency of both mechanisms remains to be verified with fine-scale analyses of both spawning/migrating aged adults and their offspring to confirm the stochastic/deterministic nature of the IBT pattern in eel.
高度洄游性海洋物种的生活史特征，如成年个体的繁殖成功率和幼体扩散，在很大程度上由海洋学和气候因素决定。然而，海洋生物在时间和空间上的扩散可能会受到限制。距离隔离模式（IBD）在海洋物种中已被多次观察到。如果产卵时间是地理位置的函数，那么时间和空间隔离很容易被混淆或误解。在本研究中，我们旨在区分影响欧洲鳗鲡（Anguilla anguilla L.）幼鱼遗传组成的各种因素。通过控制地理变异，我们评估了时间变异，并测试了不同年份内和不同年份间补充群体之间可能存在的时间隔离（IBT）。利用12个多态性等位酶位点和6个可变微卫星位点，我们发现遗传分化较低（F(ST)=0.01 - 0.002），且在不同时间样本之间差异显著。遗传距离与时间距离之间的回归分析与IBT的微妙年际模式一致。我们的数据表明，欧洲鳗鲡的种群动态可能受遗传组成时间变异的双重模式控制：（i）产卵群体的大规模IBT，这可能是鳗鲡科大型洄游回路以及成年个体年度繁殖贡献强烈变异的结果；（ii）季节性分离的产卵群体中同一年龄组内繁殖成功率的较小尺度变异（遗传斑块性），最有可能源于海洋和气候力量的波动。这两种机制的一致性仍有待通过对产卵/洄游成年个体及其后代的精细分析来验证，以确认鳗鲡IBT模式的随机/确定性本质。
