Behaviourally-mediated shifts in reef fish communities following severe disturbance

预计个体、种群和物种将迁移、适应或死亡，以应对气候变化。然而，我们对这些过程如何发挥作用的理解存在很大差距，这使得预测未来会发生什么变得困难。其中一个缺口在于动物个体行为对这些反应的贡献。然而，很难将行为纳入预测，因为尚不清楚它如何扩大规模，影响更大、更明显的生态模式。动物行为作为群落规模反应的潜在中介受到的关注相对较少，因为预测往往侧重于更大规模、更明显的影响，如物种范围转移和灭绝。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，几乎可以即时缓冲气候变化的负面影响。快速反应对于应对严重的短期干扰尤为重要；例如，我们的研究表明，在2016年珊瑚礁大规模白化事件发生后，珊瑚鱼将它们的攻击性相互作用减少了三倍，以在次优环境中节省能量。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，可以为生态系统的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产生意想不到的副作用，因为它破坏了作为社区组织基础的“交战规则”。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年有针对性的新数据收集相结合，来解决这一挑战，以创建一个前所未有的行为观察时间序列和描述生态群落的多个指标。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，以及这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匹配程度，以首次确定干扰后生态群落的重组是否由改变的行为触发。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鱼类多样性，这些鱼类积极争夺资源，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，一场强度空前的厄尔尼诺Niño事件导致整个印度洋-太平洋地区的海洋温度持续上升，导致整个热带地区出现大规模珊瑚白化和随之而来的死亡。我们现有的数据提供了（漂白前）的基线，并量化了（漂白后6-12个月）鱼类行为和多个珊瑚礁生态群落结构的最初快速变化。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，通过结合更长远的视角，探索行为如何在现实环境中调节社区变化。通过对多个地点的这些影响进行量化，我们可以确定任何观察到的变化都是由白化事件驱动的，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提供第一个强有力的理论假设和经验证据。这些结果将增强人们的理解，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.