Goetze Erica
Integrative Oceanography Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla 92093-0218, USA.
Evolution. 2005 Nov;59(11):2378-98.
Although theory dictates that limited gene flow between populations is a necessary precursor to speciation under allopatric and parapatric models, it is currently unclear how genetic differentiation between conspecific populations can arise in open-ocean plankton species. I examined two recently distinguished sympatric, circumglobal sister species, Eucalanus hyalinus and Eucalanus spinifer, for population genetic structure throughout their global biogeographic ranges. Here I show that oceanic zooplankton species can be highly genetically structured on macrogeographic spatial scales, despite experiencing extensive gene flow within features of the large-scale ocean circulation. Mitochondrial DNA analyses of 450 and 383 individuals of E. hyalinus and E. spinifer, respectively, revealed that habitat discontinuities at the boundaries of subtropical gyres in the North and South Pacific, as well as continental land masses, acted as effective barriers to gene flow for both species. However, the impact of specific barriers on population genetic structure varied between the sister species, despite their close phylogenetic relationship and similar circumglobal biogeogeographic distributions. The sister species differed in their oceanographic distributions, with E. spinifer dominating oligotrophic waters of the subtropical gyres and E. hyalinus more abundant along central water mass boundaries and in frontal zones and upwelling systems. This species-specific difference in the oceanographic habitat is an important factor determining the historical and contemporary patterns of dispersal of the two species. I suggest that species-specific ecological differences are likely to be a primary determinant of population genetic structure of open-ocean plankton.
尽管理论表明，在异域和邻域模型下，种群间有限的基因流动是物种形成的必要前提，但目前尚不清楚在开阔海洋浮游生物物种中，同种种群之间的遗传分化是如何产生的。我研究了两个最近才区分出来的同域分布、环全球的姐妹物种——透明真哲水蚤（Eucalanus hyalinus）和刺真哲水蚤（Eucalanus spinifer），以了解它们在全球生物地理范围内的种群遗传结构。在这里我表明，尽管在大规模海洋环流特征范围内经历了广泛的基因流动，但海洋浮游动物物种在宏观地理空间尺度上仍可能具有高度的遗传结构。分别对450个透明真哲水蚤个体和383个刺真哲水蚤个体进行的线粒体DNA分析表明，北太平洋和南太平洋亚热带环流边界以及大陆地块处的栖息地不连续性，对这两个物种而言都是有效的基因流动障碍。然而，尽管这两个姐妹物种具有密切的系统发育关系和相似的环全球生物地理分布，但特定障碍对种群遗传结构的影响在它们之间却有所不同。这两个姐妹物种的海洋学分布不同，刺真哲水蚤在亚热带环流的贫营养水域占主导，而透明真哲水蚤在中心水团边界、锋区和上升流系统中更为丰富。这种海洋学栖息地的物种特异性差异是决定这两个物种历史和当代扩散模式的一个重要因素。我认为，物种特异性的生态差异很可能是开阔海洋浮游生物种群遗传结构的主要决定因素。
