Comparison of population-genetic structuring in congeneric kelp- versus rock-associated snails: a test of a dispersal-by-rafting hypothesis

Phylogeographic studies indicate that many marine invertebrates lacking autonomous dispersal ability are able to achieve trans-oceanic colonization by rafting on buoyant macroalgae. However, less is known about the impact of rafting on on-going population-genetic connectivity of intertidal species associated with buoyant macroalgae. We hypothesize that such species will have higher levels of population-genetic connectivity than those exploiting nonbuoyant substrates such as rock. We tested this hypothesis by comparing nuclear multilocus population-genetic structuring in two sister topshell species, which both have a planktonic larval phase but are fairly well segregated by their habitat preference of low-tidal bull-kelp holdfasts versus mid-to-low tidal bare rock. We analyzed population samples from four sympatric sites spanning 372 km of the east coast of southern New Zealand. The sampled region encompasses a 180 km wide habitat discontinuity and is influenced by a stable, northward co...

系统地理学研究（Phylogeographic studies）表明，许多缺乏自主扩散能力的海洋无脊椎动物能够通过附着在漂浮大型藻类上漂流实现跨洋定殖。然而，对于漂流行为对与漂浮大型藻类相关的潮间带物种现存种群遗传连通性（population-genetic connectivity）的影响，目前所知仍较为有限。我们假设，此类物种的种群遗传连通性水平将高于利用岩石等非漂浮基质的物种。我们通过比较两种姐妹海螺物种的核多位点种群遗传结构（nuclear multilocus population-genetic structuring）来验证这一假设；这两种物种均具有浮游幼体阶段，但因其栖息地偏好（低潮带巨藻固着器 vs 中低潮带裸露岩石）而相对隔离。我们分析了来自新西兰南部东海岸4个同域分布位点（sympatric sites）的种群样本，这些位点跨度达372公里。采样区域包含一个180公里宽的栖息地不连续区域，并受稳定的北向流（原文此处未完整）影响。