WAMSI Node 1.2.3 - An assessment of likely dispersal patterns for marine organisms based on hydrodynamic and population genetic models

Here we predict oceanographic connectivity among four geographical locations in the south west of Western Australia using hydrodynamic modelling of larval dispersal and test these predictions against genetic descriptions of population structure, population boundaries and estimates of larval migration in two co-distributed sea urchin species. Sea urchins are excellent models for characterising marine population connectivity because of their commonness, diversity of larval life histories, ease of sampling, and ecological importance as grazers in coastal benthic habitats. Our study sampled two species, Heliocidaris erythrogramma and Phylocanthius irregularis. H. erythrogramma spawns predominantly in summer and its lecithrotrophic larvae are free swimming for 3-4 days in laboratory observations. In contrast, little is known about spawning time and larval duration in P. irregularis. The south-west corner of Australia is dominated by the Leeuwin current system, the worlds only poleward-flowing western continental boundary current. The Leeuwin current (LC) is particularly strong in the late autumn and winter months and is weaker in the summer. Strong seasonal contrasts in the LC flow pattern make it possible to generate testable predictions about the predominant direction of larvae-mediated gene flow in H. erythrogramma. Comparison of genetic structure with oceanographic model predictions allowed us to make predictions about the possible larval biology of the less well characterised urchin P. irregularis.

本研究借助幼体扩散的水动力模拟，预测澳大利亚西南部四个地理区域间的海洋连通性，并以两种同域分布海胆的种群结构、种群边界遗传特征，以及幼体迁移评估结果，对该预测进行验证。海胆因分布广泛、幼体生活史类型多样、易于采样，且作为沿海底栖生境的牧食者具有重要生态功能，是表征海洋种群连通性的理想模式生物。本研究选取了两个物种：*Heliocidaris erythrogramma* 与 *Phylocanthius irregularis*。*H. erythrogramma* 主要在夏季产卵，实验室观测显示其卵黄营养型（lecithrotrophic）幼体可自由游泳3~4天。相较而言，目前对 *P. irregularis* 的产卵时间与幼体持续时长仍知之甚少。澳大利亚西南部海域以李维斯海流系统（Leeuwin Current System）为主，该海流是全球唯一沿西大陆边缘向极流动的海流。李维斯海流（LC）在晚秋与冬季流速较强，夏季则相对较弱。李维斯海流流型存在显著的季节差异，这使得我们能够对 *H. erythrogramma* 中幼体介导的基因流的主导方向生成可验证的预测。将种群结构的遗传特征与海洋动力模型预测结果进行比对，可帮助我们对特征尚不充分的 *P. irregularis* 的潜在幼体生物学特性做出预测。