1. Anemonefish and host anemones are distributed in the shallow waters of coral reefs, and thus their existence may be affected by coastal development. The Ryukyu Archipelago includes the Okinawa and Sakishima Islands; the former has experienced extensive land reclamation and drainage in coastal areas while the latter still mostly contains natural coasts. To consider the layout of protected areas needed to conserve diversity of host anemones and anemonefish in the Ryukyu Archipelago, the community structure and coexistence mechanisms of anemones and anemonefish were compared between Okinawa and Sakishima Islands.
2. Six species of anemonefish and seven species of host anemone are distributed in both islands. Among 15 species‐pair interactions observed in six species of anemonefish in the Sakishima Islands, 14 were explained by the niche differentiation hypothesis and only one interaction was explained by the cohabitation hypothesis. In the Okinawa Islands, 13 interactions were explained by the niche differentiation hypothesis, one by the cohabitation hypothesis and one by the lottery hypothesis.
3. For both host anemones and anemonefish, β‐diversity in the Okinawa Islands was lower and had a more nested structure than that of the Sakishima Islands. β‐Diversity and its nestedness did not differ between the two regions excluding study sites adjacent to coastlines, suggesting that differences in the coastal environment affected the diversity of anemones and anemonefish in the Ryukyu Archipelago.
4. These results suggested that there is an urgent need to prioritize the conservation of reef edges, where species diversity is relatively higher than directly next to the terrestrial coastline in Okinawa Island. In the Sakishima Islands, where many natural coasts remain, a wider area from directly next to the coast out to the reef edge needs to be comprehensively protected to increase β‐diversity.

中文翻译：

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天然海岸线的丧失影响琉球群岛的海葵和寄主海葵的物种多样性

1. 海葵和寄主海葵分布在珊瑚礁的浅水区，因此它们的存在可能会受到沿海发展的影响。琉球群岛包括冲绳和崎岛。前者在沿海地区经历了广泛的土地开垦和排水，而后者仍主要包含自然海岸。为了考虑到保护琉球群岛宿主海葵和海葵的多样性所需要的保护区的布局，比较了冲绳岛和崎岛群岛海葵和海葵的群落结构以及共存机制。
2. 在两个岛屿中分布着六种银莲花和七种寄主银莲花。在Sakishima群岛的6种海葵鱼中观察到的15个种对相互作用中，有14种是由生态位分化假说解释的，而只有一种是由同居假说解释的。在冲绳群岛，利基分化假说解释了13种相互作用，同居假说解释了一种相互作用，彩票论则解释了一种相互作用。
3. 对于寄主海葵和海葵鱼，冲绳群岛的β多样性较低，并且嵌套结构比崎岛群岛更丰富。除与海岸线相邻的研究地点以外的两个地区之间，β多样性及其嵌套性没有差异，这表明沿岸环境的差异影响了琉球群岛海葵和海葵的多样性。
4. 这些结果表明，迫切需要优先保护礁石边缘，因为这里的物种多样性相对比直接在冲绳岛陆地海岸线附近更高。在拥有许多自然海岸的Sakishima群岛上，需要全面保护从紧邻海岸到礁石边缘的更广阔区域，以增加β多样性。