Long-distance dispersal (LDD) is an essential event for species colonization and expansion in oceanic island ecosystems. Endozoochory by birds is an important factor promoting the LDD of plant seeds, but its contribution to interisland seed dispersal is still unclear. Here, we show possible seed dispersal by a seed predator pigeon, the Japanese wood pigeon Columba janthina, among oceanic islands in the Izu archipelago, Japan. Although some previous studies showed that most seeds swallowed by this pigeon are crushed, intact seeds were found in 44.5% of pigeon feces, indicating the contribution of these birds to seed dispersal. Seasonal population fluctuations and movements by pigeons between neighbouring islands which are 4 km apart by pigeons can promote interisland seed dispersal. We found seeds from fruiting trees not located on the islands where the pigeon feces were collected, which could have been transported from another island. Although many tree species overlap their fruiting phenology with pigeon movement between islands, the seeds of only six species were dispersed by pigeons, and most of the dispersed seeds were from species with small seeds less than 1.5 mm in diameter. Fruit consumption and frequent interisland movement of Japanese wood pigeons might homogenize the distribution of plants with small seeds among neighboring islands. In contrast, their intensive seed consumption might disturb the recruitment of plants with large seeds and make their expansion to other islands difficult. Such effects of mutualistic (dispersal) and antagonistic (predation) interactions with highly mobile seed predators may modify plant distributions and gene flow in oceanic archipelagos.

中文翻译：

---

高度移动的种子捕食者有助于海洋群岛内的岛际种子传播

远距离扩散（LDD）是海洋岛屿生态系统中物种定殖和扩张的重要事件。鸟类内生动物是促进植物种子LDD的重要因素，但其对岛间种子传播的贡献尚不清楚。在这里，我们展示了种子捕食者鸽子日本木鸽Columba janthina可能传播的种子，在日本伊豆群岛的海洋岛屿之间。虽然之前的一些研究表明，这只鸽子吞下的大多数种子都被压碎了，但在 44.5% 的鸽子粪便中发现了完整的种子，这表明这些鸟对种子传播的贡献。季节性种群波动和鸽子在相距 4 公里的相邻岛屿之间的迁徙可以促进岛际种子传播。我们发现果树的种子不在收集鸽子粪便的岛屿上，这些种子可能是从另一个岛屿运来的。虽然许多树种的结果物候与鸽子在岛屿间的移动重叠，但只有6个树种的种子被鸽子散播，大部分散播的种子来自直径小于1.5毫米的小种子。日本木鸽的水果消费和频繁的岛间移动可能会使相邻岛屿之间带有小种子的植物分布均匀化。相反，它们密集的种子消耗可能会干扰具有大种子的植物的补充，并使其难以扩展到其他岛屿。与高度移动的种子捕食者相互作用的这种互惠（分散）和对抗（捕食）相互作用的影响可能会改变海洋群岛中的植物分布和基因流动。