Behaviourally-mediated shifts in reef fish communities following severe disturbance

预计个人、种群和物种将因气候变化而迁移、适应或死亡。然而，我们对这些过程如何发挥作用的理解存在很大差距，因此很难预测未来会发生什么。一个缺口在于个体动物行为对这些反应的贡献。然而，它一直很难在预测中包括行为，因为它是如何扩大规模，影响更大，更明显的生态模式是不清楚的。动物行为作为一个潜在的调解人社区规模的反应得到了相对较少的关注，因为预测往往侧重于更大规模，更明显的影响，如物种范围的变化和灭绝。然而，行为可以提供一个重要的拼图，因为它可以比生理耐受性更快地改变，几乎可以瞬间缓冲气候变化的负面影响。快速反应对于科普严重的短期干扰尤为重要;例如，我们的研究表明，在2016年珊瑚礁大规模漂白事件之后，珊瑚鱼减少了三倍的攻击性相互作用，以在次优环境中保存能量。虽然行为改变可能不会带来持久的解决方案，但在这种情况下，它提供的缓冲可能至关重要，可以为生态系统恢复或长期生理适应的发展赢得额外的时间。然而，快速的行为反应也可能会破坏社区组织基础的“参与规则”，从而产生意想不到的副作用。因此，我们必须缩小这一知识差距，以便准确理解和预测物种对气候变化的反应。我们的项目通过将自然干扰实验之前和之后6-12个月收集的现有经验数据与干扰后3-4年有针对性地收集的新数据相结合，创建一个前所未有的行为观察和多个指标，描述生态社区的时间序列。此外，我们将创建理论模型来揭示攻击行为的变化是否以及如何改变不同物种个体之间的相互作用，以及如何扩大规模以重新组织生态群落。最后，我们将测试这些理论预测与实地数据的吻合程度，以首次确定干扰后生态群落的重组是否是由改变的行为引发的。珊瑚礁提供了一个很好的模型系统来测试这些问题，因为它们拥有令人难以置信的多样性，这些鱼类积极地争夺资源，这被认为是构建更广泛的珊瑚礁鱼类群落的重要过程。2016年，一场强度空前的厄尔尼诺现象导致整个印度洋-太平洋地区的海洋温度持续上升，导致大规模珊瑚白化，随后导致整个热带地区的死亡。我们现有的数据提供了一个基线（漂白前），并量化了（漂白后6-12个月），鱼类行为和生态群落结构在多个珊瑚礁的初始快速变化。因此，我们现在有一个独特的机会，利用这个罕见的，大规模的自然实验，探索行为如何通过纳入一个长期的观点，在现实环境中调解社区的变化。通过在多个地点量化这些影响，我们可以确定任何观察到的变化都是由漂白事件驱动的，而不是珊瑚礁之间的其他环境或地质差异。我们的工作将产生第一个强大的理论假设和经验证据，说明行为如何介导更广泛的生态系统。研究结果将提高人们的理解，并使生态学家能够将行为纳入物种对气候变化反应的预测中。

Individuals, populations and species are expected to move, adapt or die in response to climate change. However, there are big gaps in our understanding of how these processes play out, making it difficult to predict what will happen in the future. One gap lies in the contribution of individual animal behaviour to these responses. However, it has been difficult to include behaviour in predictions because it is unclear how it scales-up to influence larger, more visible ecological patterns.Animal behaviour has received relatively little attention as a potential mediator of community-scale responses because predictions tend to focus on larger-scale, more visible impacts, such as species range shifts and extinctions. However, behaviour could provide an important piece of the puzzle because it can be modified much more rapidly than physiological tolerance, providing an almost instantaneous buffer against negative effects of climate change. Rapid responses are particularly important to cope with severe short-term disturbances; for example, our research has shown that following the coral reef mass bleaching event in 2016, reef fish decreased their aggressive interactions three-fold to conserve energy in what became a suboptimal environment. Whilst behavioural change might not deliver a lasting solution, the buffer it provides could be critical in such cases to buy extra time for ecosystem recovery or for longer-term physiological adaptations to develop. Yet rapid behavioural responses could also create unintended side effects by disrupting the "rules of engagement" that underlie community organisation. Therefore, it is imperative that we close this knowledge gap to enable accurate understanding and future predictions of species responses to climate change.Our project addresses this challenge by combining existing empirical data collected before and 6-12 months after a natural disturbance experiment with targeted collection of new data 3-4 years after the disturbance, to create an unprecedented time series of behavioural observations and multiple metrics that describe the ecological community. In addition, we will create theoretical models to reveal if and how changes in aggressive behaviour can alter the interactions between individuals of different species, and how this can scale up to re-organise ecological communities. Finally, we will test how closely these theoretical predictions match the field data to establish for the first time whether re-organisation of ecological communities following disturbance is triggered by modified behaviour.Coral reefs offer an excellent model system to test these questions because they host an incredible diversity of fishes that fight aggressively for access to resources, which is thought to be an important process for structuring the wider reef fish community. In 2016, an extended El Niño event of unprecedented strength led to sustained increases in ocean temperature throughout the Indo-Pacific, causing mass coral bleaching and subsequent mortality across the tropics. Our existing data provides a baseline for (before bleaching), and quantifies the initial rapid changes in (6-12 months after bleaching), fish behaviour and the structure of ecological communities across multiple reefs. As a result, we now have a unique opportunity to use this rare, large-scale natural experiment to explore how behaviour mediates community shifts in a realistic setting by incorporating a longer-term perspective. By quantifying these impacts in multiple locations, we can be sure that any observed changes are driven by the bleaching event, rather than other environmental or geological differences between reefs. Our work will generate the first robust theoretical hypotheses and empirical evidence for how behaviour mediates the wider ecosystem. The results will enhance understanding and enable ecologists to incorporate behaviour into predictions of species responses to climate change.