Triest Ludwig, Sierens Tim, Menemenlis Dimitris, Van der Stocken Tom
Ecology and Biodiversity Research Group, Plant Biology and Nature Management, Vrije Universiteit Brussel, Brussels, Belgium.
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States.
Front Plant Sci. 2018 Jun 13;9:806. doi: 10.3389/fpls.2018.00806. eCollection 2018.
Coastal salt- and brackish water lagoons are unique shallow habitats characterized by beds of submerged seagrasses and salt-tolerant species. Established long-term and large-scale patterns of connectivity in lagoon systems can be strongly determined by patterns of nearshore and coastal currents next to local bird-mediated seed dispersal. Despite the importance of dispersal in landscape ecology, characterizing patterns of connectivity remains challenging in aquatic systems. Here, we aimed at inferring connectivity distances of along European coastal lagoons using a population genetic imprint and modeled dispersal trajectories using an eddy-resolving numerical ocean model that includes tidal forcing. We investigated 1,303 individuals of 46 populations alongside subbasins of the Mediterranean (Balearic, Tyrrhenian, Ionian) and the Atlantic to Baltic Sea coastline over maximum distances of 563-2,684 km. Ten microsatellite loci under an autotetraploid condition revealed a mixed sexual and vegetative reproduction mode. A pairwise permutation test of populations revealed high levels of historical connectivity only for distance classes up to 104-280 km. Since full range analysis was not fully explanatory, we assessed connectivity in more detail at coastline and subbasin level using four approaches. Firstly, a regression over restricted geographical distances (300 km) was done though remained comparable to full range analysis. Secondly, piecewise linear regression analyses yielded much better explained variance but the obtained breakpoints were shifted toward greater geographical distances due to a flat slope of regression lines that most likely reflect genetic drift. Thirdly, classification and regression tree analyses revealed threshold values of 47-179 km. Finally, simulated ocean surface dispersal trajectories for propagules with floating periods of 1-4 weeks, were congruent with inferred distances, a spatial Bayesian admixed gene pool clustering and a barrier detection method. A kinship based spatial autocorrelation showed a contemporary within-lagoon connectivity up to 20 km. Our findings indicate that strong differentiation or admixtures shaped historical connectivity and that a pre- and post LGM genetic imprint of along the European coasts was maintained from their occurrence in primary habitats. Additionally, this study demonstrates the importance of unraveling thresholds of genetic breaks in combination with ocean dispersal modeling to infer patterns of connectivity.
沿海咸水和微咸水泻湖是独特的浅水栖息地，其特征是有水下海草床和耐盐物种。泻湖系统中已确立的长期和大规模连通模式，可能会受到近岸和沿岸海流模式以及当地鸟类介导的种子传播的强烈影响。尽管扩散在景观生态学中很重要，但在水生系统中描述连通模式仍然具有挑战性。在这里，我们旨在利用种群遗传印记推断欧洲沿海泻湖的连通距离，并使用包含潮汐强迫的涡旋分辨数值海洋模型模拟扩散轨迹。我们调查了地中海（巴利阿里海、第勒尼安海、爱奥尼亚海）和大西洋至波罗的海海岸线子流域的46个种群的1303个个体，最大距离为563 - 2684公里。在同源四倍体条件下的10个微卫星位点显示出有性繁殖和营养繁殖的混合模式。对种群的成对排列检验表明，仅在距离类别达104 - 280公里时存在高水平的历史连通性。由于全范围分析并不完全具有解释性，我们使用四种方法在海岸线和子流域层面更详细地评估连通性。首先，对有限地理距离（300公里）进行回归分析，不过结果仍与全范围分析具有可比性。其次，分段线性回归分析产生了更好的可解释方差，但由于回归线斜率平缓（很可能反映了遗传漂变），得到的断点向更大的地理距离偏移。第三，分类和回归树分析揭示了47 - 179公里的阈值。最后，对漂浮期为1 - 4周的繁殖体的模拟海洋表面扩散轨迹，与推断距离、空间贝叶斯混合基因库聚类和障碍检测方法一致。基于亲缘关系的空间自相关显示当代泻湖内连通性可达20公里。我们的研究结果表明，强烈的分化或混合塑造了历史连通性，并且末次盛冰期前后欧洲海岸沿线的遗传印记从它们在原生栖息地出现时就得以保留。此外，本研究证明了结合海洋扩散模型揭示遗传断点阈值以推断连通模式的重要性。
