Widespread prevalence of cryptic Symbiodinium D in the key Caribbean reef builder, Orbicella annularis
Widespread prevalence of cryptic Symbiodinium D in the key Caribbean reef builder, Orbicella annularis
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DOI：
10.1007/s00338-015-1264-4
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发表时间：
2015-06-01
期刊：
影响因子：
3.5
通讯作者：
Stevens, Jamie R.
中科院分区：
文献类型：
--
作者：
Kennedy, Emma V.;Foster, Nicola L.;Stevens, Jamie R.
共生藻D，一个相对罕见的进化枝的藻类内共生体与全球分布，已引起人们的兴趣，因为它的一些亚进化枝类型诱导增加的耐热性和相关的权衡，包括在其珊瑚宿主的生长速度降低。越来越多的报道称，共生藻D的成员组成了低丰度的“神秘”（<10%）比例的混合珊瑚内共生体群落，具有未知的生态影响。针对特定类型的实时PCR（RT-PCR）足够灵敏以检测这些背景共生体水平。在这项研究中，RT-PCR被用来筛选552个加勒比海珊瑚礁建造者Orbicella annularis的菌落，这些菌落在540万公里（2）范围内取样，以寻找隐蔽的共生藻“D1”（即，主要的加勒比ITS 2变体，D1和D1-4）。在33个被分析的种群中，除了一个种群外，所有种群都显示出共生藻D1的低丰度，每个地点平均有> 30%的珊瑚被发现窝藏共生体。当使用常规筛选技术，变性梯度凝胶电泳分析相同的样品时，仅在12个种群中检测到共生odinium D1，并且似乎由<12%的存在的菌落主持（与其他报道的O. annularis）。隐共生藻D1在整个加勒比地区的分布基本上是均匀的，尽管中美洲堡礁珊瑚中隐共生藻D1的数量比预期的要多得多，这可能是1998年该地区强烈变暖的结果。耐热共生藻在O. annularis可能反映了珊瑚通过共生体改组暂时应对变暖事件的能力。然而，与珊瑚钙化减少的联系意味着共生藻D1在O.在保持珊瑚礁生长对维持珊瑚礁生态系统功能至关重要的时候，环纹珊瑚种群不太可能阻止珊瑚礁健康状况的长期下降。
Symbiodinium D, a relatively rare clade of algal endosymbiont with a global distribution, has attracted interest as some of its sub-cladal types induce increased thermal tolerance and associated trade-offs, including reduced growth rate in its coral hosts. Members of Symbiodinium D are increasingly reported to comprise low-abundance 'cryptic' (< 10 %) proportions of mixed coral endosymbiont communities, with unknown ecological implications. Real-time PCR (RT-PCR) targeted to specific types is sufficiently sensitive to detect these background symbiont levels. In this study, RT-PCR was employed to screen 552 colonies of the key Caribbean reef builder Orbicella annularis sampled across a 5.4 million km(2) range for the presence of cryptic Symbiodinium 'D1' (i.e., the principal Caribbean ITS2 variants, D1 and D1-4). All but one out of 33 populations analysed were shown to host low abundances of Symbiodinium D1, with an average of > 30 % of corals per site found to harbour the symbiont. When the same samples were analysed using the conventional screening technique, denaturing gradient gel electrophoresis, Symbiodinium D1 was only detected in 12 populations and appeared to be hosted by < 12 % of colonies where present (in agreement with other reported low prevalence/absences in O. annularis). Cryptic Symbiodinium D1 showed a mainly uniform distribution across the wider Caribbean region, although significantly more Mesoamerican Barrier Reef corals hosted cryptic Symbiodinium D1 than might be expected by chance, possibly as a consequence of intense warming in the region in 1998. Widespread prevalence of thermally tolerant Symbiodinium in O. annularis may potentially reflect a capacity for the coral to temporarily respond to warming events through symbiont shuffling. However, association with reduced coral calcification means that the ubiquitous nature of Symbiodinium D1 in O. annularis populations is unlikely to prevent long-term declines in reef health, at a time when maintaining reef growth is vital to sustain reef ecosystem function.