Santos S R, Shearer T L, Hannes A R, Coffroth M A
Department of Biological Science, State University of New York at Buffalo, Buffalo, NY 14260, USA.
Mol Ecol. 2004 Feb;13(2):459-69. doi: 10.1046/j.1365-294x.2003.02058.x.
The success of coral reefs is due to obligate mutualistic symbioses involving invertebrates and photosynthetic dinoflagellate symbionts belonging to the genus Symbiodinium. In the Caribbean, the vast majority of octocorals and other invertebrate hosts associate with Symbiodinium clade B, and more selectively, with a single lineage of this clade, Symbiodinium B1/B184. Although B1/B184 represents the most prevalent Symbiodinium in the Caribbean, there is little evidence supporting fine-scale diversity and host-alga specificity within this lineage. We explored simultaneously the questions of diversity and specificity in Symbiodinium B1/B184 by sequencing the flanking regions of two polymorphic microsatellites from a series of Symbiodinium clade B cultures along with Symbiodinium B1/B184 populations of the octocorals Pseudopterogorgia elisabethae, P. bipinnata and Gorgonia ventalina. Seven unique sequence variants were identified based on concatenation of the two loci. Phylogenetic analyses of these variants, which we refer to as phylotypes, recognized five as belonging to B1/B184, thus providing the first evidence of distinct taxa within this Symbiodinium lineage. Furthermore, sympatric P. elisabethae and P. bipinnata at San Salvador in the Bahamas were found to harbour distinct Symbiodinium B1/B184 phylotypes, demonstrating unequivocally the existence of fine-scale specificity between Caribbean octocorals and these algae. Taken together, this study exemplifies the complex nature of Symbiodinium biodiversity and specificity.
珊瑚礁的成功归因于无脊椎动物与属于共生藻属的光合甲藻共生体之间的专性互利共生关系。在加勒比地区，绝大多数八放珊瑚和其他无脊椎动物宿主与B类共生藻相关联，更具选择性地是与该类群的一个单一谱系——共生藻B1/B184相关联。尽管B1/B184是加勒比地区最普遍的共生藻，但几乎没有证据支持该谱系内的精细尺度多样性和宿主 - 藻类特异性。我们通过对一系列B类共生藻培养物以及八放珊瑚华丽软柳珊瑚、双羽软柳珊瑚和扇形柳珊瑚的共生藻B1/B184群体的两个多态微卫星侧翼区域进行测序，同时探讨了共生藻B1/B184中的多样性和特异性问题。基于两个位点的串联鉴定出了七个独特的序列变体。对这些我们称为系统型的变体进行系统发育分析，识别出其中五个属于B1/B184，从而首次提供了该共生藻谱系内不同分类群的证据。此外，在巴哈马圣萨尔瓦多同域分布的华丽软柳珊瑚和双羽软柳珊瑚被发现含有不同的共生藻B1/B184系统型，明确证明了加勒比八放珊瑚与这些藻类之间存在精细尺度的特异性。综上所述，这项研究例证了共生藻生物多样性和特异性的复杂本质。
