Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, Dunedin 9016, New Zealand.
Mol Ecol. 2010 Oct;19(20):4572-80. doi: 10.1111/j.1365-294X.2010.04842.x. Epub 2010 Sep 28.
Coastal populations are often connected by unidirectional current systems, but the biological effects of such asymmetric oceanographic connectivity remain relatively unstudied. We used mtDNA analysis to determine the phylogeographic origins of beach-cast bull-kelp (Durvillaea antarctica) adults in the Canterbury Bight, a 180 km coastal region devoid of rocky-reef habitat in southern New Zealand. A multi-year, quantitative analysis supports the oceanographically derived hypothesis of asymmetric dispersal mediated by the north-flowing Southland Current. Specifically, 92% of beach-cast specimens examined had originated south of the Bight, many drifting north for hundreds of kilometres, and some traversing at least 500 km of ocean from subantarctic sources. In contrast, only 8% of specimens had dispersed south against the prevailing current, and these counter-current dispersers likely travelled relatively small distances (tens of kilometres). These data show that oceanographic connectivity models can provide robust estimates of passive biological dispersal, even for highly buoyant taxa. The results also indicate that there are no oceanographic barriers to kelp dispersal across the Canterbury Bight, indicating that other ecological factors explain the phylogeographic disjunction across this kelp-free zone. The large number of long-distance dispersal events detected suggests drifting macroalgae have potential to facilitate ongoing connectivity between otherwise isolated benthic populations.
沿海地区的种群通常由单向的海流系统连接，但这种不对称的海洋连通性的生物学效应仍相对未被研究。我们使用 mtDNA 分析来确定新西兰南部坎特伯雷湾海滩上丢弃的巨型巨藻（Durvillaea antarctica）成年个体的系统地理学起源，该湾是一个 180 公里长的沿海地区，没有岩石礁石栖息地。一项多年的定量分析支持了由北流的南地海流介导的不对称扩散的海洋学假设。具体来说，92%的被检查的海滩丢弃样本起源于比尔特以南，许多向北漂流数百公里，有些则从亚南极地区穿过至少 500 公里的海洋。相比之下，只有 8%的样本是与主流相反的向南扩散，这些逆流扩散者可能只移动了相对较小的距离（几十公里）。这些数据表明，海洋连通性模型可以为被动生物扩散提供可靠的估计，即使对于高度浮性的类群也是如此。结果还表明，巨型巨藻在坎特伯雷湾的扩散没有海洋障碍，这表明其他生态因素解释了这个无巨藻区的系统地理学间断。大量远距离扩散事件的检测表明，漂流的大型藻类有可能促进原本孤立的底栖种群之间的持续连通。
