Competitive dominance by tabular corals: an experimental analysis of recruitment and survival of understorey assemblages
Competitive dominance by tabular corals: an experimental analysis of recruitment and survival of understorey assemblages
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DOI：
10.1016/s0022-0981(00)00209-4
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发表时间：
2000-08-23
影响因子：
2
通讯作者：
Hughes, TP
中科院分区：
文献类型：
--
作者：
Baird, AH;Hughes, TP
鹿角珊瑚属的斑珊瑚和鹿角珊瑚经常在浅层珊瑚礁上形成低多样性的林分，大概是由于它们的生长速度快，并且有能力胜过下层植物组合。在丰富的印太板状珊瑚（Acropora hyacinthus）下面的珊瑚覆盖面积，比大堡礁北部蜥蜴岛（Lizard Island）礁顶附近的底层低四倍。我们通过放置实验板和珊瑚碎片在风信子的大菌落下，研究了风信子对其招募和死亡模式的影响。8周后，风信子下的珊瑚、丝状藻类和甲壳藻（CCA）的招募量分别比露天板低96%、85%和50%。相比之下，双壳类和多毛类在不同处理下的招募量是均匀的，而苔藓虫在风信草下的招募量是露天处理下的4倍。因此，在a . hyncinthus下面的珊瑚招募率低，似乎不是由于在桌子下面产卵的幼虫减少。相反，光养和异养分类群之间的差异表明，风信子下光照水平的降低是招募组合差异的部分原因。为了检验风信子对已建立生物的早期死亡率和生长的影响，我们在露天放置招募板9周，然后在风信子下再移植8周。在桌子下面的幼珊瑚的存活率不到那些在没有阴影的珊瑚礁顶部的控制面板上的一半。此外，移植面板上的藻皮和CCA丰度明显降低。相比之下，无论处理方式如何，异养生物的覆盖面积都有所增加。中间Acropora intermedia和大角Pocillopora damicornis的实验分支片段移植到风信子下后，与相邻的未遮荫对照相比，成活率也较差。我们的结论是，风信子是一个强大的竞争对手，它通过过度生长杀死邻近的珊瑚，并通过减少珊瑚的补充来抢占未来的竞争。(C) 2000 Elsevier Science BN。版权所有。
Tabular and staghorn corals of the genus Acropora often form low-diversity stands on shallow coral reefs, presumably due to their rapid growth rate and ability to outcompete understorey assemblages. Coral cover underneath the abundant Indo-Pacific tabular coral, Acropora hyacinthus, was four times lower than on the adjacent substratum on the reef crest at Lizard Island on the northern Great Barrier Reef. We investigated the effect of A. hvacinthlts on patterns of recruitment and mortality by placing experimental panels and coral fragments underneath large colonies of A. hyacinthus. After 8 weeks, recruitment of corals, filamentous algae and crustose coralline algae (CCA) underneath A. hyacinthus was 96, 85 and 50% lower, respectively, compared to panels placed in the open. In contrast, recruitment by bivalves and polychaetes was uniform among treatments, while bryozoans recruited four times more abundantly under A. hyacinthus than in the open. Consequently, the low rate of recruitment by corals beneath A. hyncinthus does not appear to be due to a reduction in the delivery of larvae underneath tables. Instead, the disparity between phototrophic and heterotrophic taxa suggests that diminished Light levels under A. hyacinthus are partially responsible for the divergence in recruit assemblages. To test the effect of A. hyacinthus on early mortality and growth of established organisms, recruitment panels were placed on the open for 9 weeks then transplanted underneath A. hyacinthus for a further 8 weeks. The survivorship of juvenile corals underneath tables was less than half that of those on control panels on the unshaded reef crest. Furthermore, the abundance of algal turfs and CCA was sharply lower on transplanted panels. In contrast, heterotrophic organisms increased in cover, regardless of treatment. Experimental branch fragments of Acropora intermedia and Pocillopora damicornis also survived poorly following transplantation underneath A. hyacinthus, compared to adjacent, unshaded controls. We conclude that A. hyacinthus is a formidable competitor which call kill neighbouring corals by overgrowing them, and pre-empt future competition by reducing coral recruitment. (C) 2000 Elsevier Science BN. All rights reserved.