Coyer J A, Peters A F, Hoarau G, Stam W T, Olsen J L
Department of Marine Biology, Centre of Ecology and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands.
Proc Biol Sci. 2002 Sep 7;269(1502):1829-34. doi: 10.1098/rspb.2002.2093.
Historically, the intertidal seaweeds Fucus serratus (Fs) and Fucus evanescens (Fe) were sympatric only along the western coast of Norway. In the mid-1890s, Fe (monoecious) was accidentally introduced into the Oslofjord. Putative hybridization with the endemic Fs (dioecious) was observed in Oslofjord by 1977 and in the Kattegat and western Baltic Seas by 1998. At Blushøj, Denmark (Kattegat Sea) putative Fs x Fe hybrids were present only when densities of Fe and Fs exceeded 14 and 2 m(-2), respectively. All of the 58 putative hybrids that were collected in 1999 were dioecious and intermediate in morphology. Essentially all (57 out of 58) were reproductively mature, but the oogonia possessed fewer and more variably sized eggs than either parent. Examination of each parental species and putative hybrids with nuclear, mitochondrial and chloroplast molecular markers confirmed the occurrence of hybridization. Furthermore, all of the hybrids possessed Fe-type chloroplasts and mitochondria, indicating that only the Fe egg x Fs sperm pairing was successful in the field. The reciprocal cross of Fs egg x Fe sperm was absent in the field and significantly less successful in laboratory crossings. Asymmetrical hybridization has also been reported for several species of plants and animals.
从历史上看，潮间带海藻锯齿墨角藻（Fs）和消失墨角藻（Fe）仅在挪威西海岸同域分布。在19世纪90年代中期，Fe（雌雄同体）被意外引入奥斯陆峡湾。到1977年在奥斯陆峡湾观察到其与当地的Fs（雌雄异体）可能发生了杂交，到1998年在卡特加特海峡和波罗的海西部也观察到了这种情况。在丹麦的布卢绍伊（卡特加特海峡），仅当Fe和Fs的密度分别超过14株/平方米和2株/平方米时才出现可能的Fs×Fe杂种。1999年采集的58个可能的杂种全部为雌雄异体，形态上为中间型。基本上所有（58个中的57个）都已生殖成熟，但卵囊中的卵比任何一个亲本都少且大小变化更大。用核、线粒体和叶绿体分子标记对每个亲本物种和可能的杂种进行检测，证实了杂交的发生。此外，所有杂种都具有Fe型叶绿体和线粒体，这表明在自然环境中只有Fe卵子×Fs精子的配对是成功的。在自然环境中不存在Fs卵子×Fe精子的反向杂交，在实验室杂交中成功率也显著较低。对于几种动植物也有不对称杂交的报道。
