Geographic parthenogenesis in the brown alga Scytosiphon lomentaria (Scytosiphonaceae): Sexuals in warm waters and parthenogens in cold waters

Geographic parthenogenesis, a phenomenon where parthenogens and their close sexual relatives inhabit distinct geographic areas, has been considered an interesting topic in evolutionary biology. Reports of geographic parthenogenesis from land and freshwater are numerous, however, this occurrence has been rarely reported from the sea. Brown algae are mostly marine and are thought to include numerous obligate parthenogens; still, little is known about the distribution, origin, and evolution of parthenogens in this group. Here we report a novel pattern of geographic parthenogenesis in the isogamous brown alga Scytosiphon lomentaria. Sex ratio investigation demonstrated that, in Japan, sexual populations grew in the coast along warm ocean currents, whereas female-dominant parthenogenetic populations grew mainly in the coast along a cold ocean current. In the two localities where sexual and parthenogenetic populations were parapatric, parthenogens grew in more wave-exposed areas than sexuals....

地理孤雌生殖（geographic parthenogenesis）是指孤雌生殖个体（parthenogens）与其近缘有性类群占据截然不同地理分布区的现象，长期以来都是进化生物学领域的热门研究课题。目前关于陆地与淡水生境中地理孤雌生殖的报道数量颇丰，但海洋环境中的此类现象却鲜有记载。褐藻（brown algae）大多为海洋生物，且被认为包含诸多专性孤雌生殖类群，但学界对该类群孤雌生殖个体的分布、起源与演化机制仍知之甚少。本研究报道了同配生殖（isogamous）褐藻带形水云（Scytosiphon lomentaria）中一种全新的地理孤雌生殖模式。性别比例调查结果显示，在日本海域，有性生殖种群分布于暖流流经的沿岸区域，而以雌性占优的孤雌生殖种群则主要栖息于寒流流经的沿岸地带。在有性与孤雌生殖种群呈邻域分布（parapatric）的两个采样点中，孤雌生殖个体的栖息生境较有性生殖类群更为暴露于海浪冲击之下。