Behaviourally-mediated shifts in reef fish communities following severe disturbance

预计个人、种群和物种将迁徙、适应或死亡，以应对气候变化。然而，我们对这些过程如何发展的理解存在很大差距，这使得我们很难预测未来会发生什么。其中一个差距在于个体动物行为对这些反应的贡献。然而，很难将行为包括在预测中，因为还不清楚它如何扩大到影响更大、更明显的生态模式。动物行为作为社区规模反应的潜在调解人，受到的关注相对较少，因为预测往往集中在更大规模、更明显的影响上，如物种范围的变化和灭绝。然而，行为可能提供了一个重要的谜题，因为它可以比生理耐受性更快地改变，提供几乎瞬间的缓冲，抵御气候变化的负面影响。快速反应对于应对严重的短期干扰特别重要；例如，我们的研究表明，在2016年珊瑚礁大规模白化事件之后，珊瑚鱼为了在次优环境中保存能量，将它们的攻击性相互作用减少了三倍。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，它提供的缓冲可能是为生态系统恢复或长期生理适应发展争取额外时间的关键。然而，快速的行为反应也可能产生意想不到的副作用，因为它扰乱了支撑社区组织的“参与规则”。因此，我们必须弥合这一知识鸿沟，以便能够准确地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年的有针对性的新数据收集相结合来应对这一挑战，以创建史无前例的行为观察和描述生态群落的多种度量的时间序列。此外，我们将创建理论模型，揭示攻击性行为的变化是否以及如何改变不同物种个体之间的互动，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现场数据的匹配程度，以首次确定干扰后生态群落的重新组织是否由行为改变引发。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的鱼类，它们积极争夺资源，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，一场强度空前的长期厄尔尼诺事件导致整个印度洋-太平洋地区的海洋温度持续上升，导致整个热带地区的大规模珊瑚白化和随后的死亡。我们现有的数据提供了(漂白前)的基线，并量化了漂白后(漂白后6-12个月)的初始快速变化、鱼类行为和多个珊瑚礁的生态群落结构。因此，我们现在有了一个独特的机会，可以利用这个罕见的大规模自然实验，通过纳入更长期的视角，来探索行为如何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。我们的工作将为行为如何调节更广泛的生态系统产生第一个强有力的理论假设和经验证据。这一结果将增进理解，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.