Ricardo Gerard, Doropoulos Christopher, Babcock Russell C, Buccheri Elizabeth, Khalil Andrew, Mumby Peter J
Marine Spatial Ecology Lab, School of the Environment, The University of Queensland, St. Lucia, Queensland, Australia.
CSIRO Environment, St. Lucia, Queensland, Australia.
Nat Ecol Evol. 2025 Sep 2. doi: 10.1038/s41559-025-02844-y.
Climate change and other anthropogenic stressors have severe impacts on the ecological functioning of marine ecosystems by causing widespread declines in population sizes and, for surviving individuals, limiting the capacity for population recovery through sexual reproduction. Ecological theory suggests that affected populations can suffer local extinction because of Allee effects, where reduced population densities prevent gamete encounters, resulting in reproductive failure. Without understanding the relationship between the density or spacing of spawning individuals and fertilization success, coral reefs may unknowingly pass a critical population threshold, further complicating conservation efforts. In this study we conducted a series of independent manipulative field experiments using three common simultaneous hermaphroditic spawning Acropora species in two locations (One Tree Island, Great Barrier Reef, and Ngermid Bay, Palau) to assess evidence of Allee effects in small populations. Experimental 'patches' of corals were structured with mean intercolonial distances ranging from 1 m to 2 m, resulting in low but measurable fertilization success (1.2-8.7%). We developed a mechanistic coral fertilization model and validated its predictions against this empirical data, finding close alignment. Depending on the species and their colony size, the model predicts that adult coral densities need to exceed 13-50 colonies per 100 m for reefs to ensure 10% fertilization success.
气候变化和其他人为压力源对海洋生态系统的生态功能产生了严重影响，导致种群数量普遍下降，而且对于存活下来的个体而言，限制了通过有性繁殖实现种群恢复的能力。生态理论表明，受影响的种群可能会因阿利效应而局部灭绝，即种群密度降低会阻碍配子相遇，从而导致繁殖失败。如果不了解产卵个体的密度或间距与受精成功率之间的关系，珊瑚礁可能会在不知不觉中越过关键的种群阈值，使保护工作更加复杂。在本研究中，我们在两个地点（大堡礁的一棵树岛和帕劳的恩格米德湾）对三种常见的同步雌雄同体产卵的鹿角珊瑚物种进行了一系列独立的现场操纵实验，以评估小种群中阿利效应的证据。实验性的珊瑚“斑块”构建为平均群体间距离在1米至2米之间，导致受精成功率较低但可测量（1.2% - 8.7%）。我们开发了一个珊瑚受精机制模型，并根据这些实证数据验证了其预测结果，发现两者非常吻合。根据物种及其群体大小，该模型预测，为确保10%的受精成功率，珊瑚礁的成年珊瑚密度需要超过每100平方米13 - 50个群体。
