BREAKDOWN: The regulation of breakdown of cooperation among species

物种间的合作--或互利共生--推动了生命之树上一些最重要的创新，并为我们提供了关键的生态系统服务。虽然人们已经投入了大量的努力来理解互惠是如何产生的，但令人惊讶的是，我们对导致互惠崩溃的原因知之甚少。互惠共生为什么以及何时会崩溃？失去互利共生的物种在进化上的直接后果是什么？我过去的研究表明，伴侣依赖的程度是宏观进化尺度上互利共生崩溃的一个关键预测因素，兼性血统更容易被抛弃。然而，解释这种宏观进化模式的潜在机制尚不清楚。因此，我的项目的目标是测试生态过程，并揭示互利主义崩溃的进化后果。为了实现这一目标，我将利用附生Rubiaceae植物（Hydnophytinae）和蚂蚁之间的互惠系统，其中涉及一个相当大的分支中的独立互惠分解事件的异常数量。我的团队将首先通过实验测试兼性物种与专性物种的生理和性状（目标1）以及基因表达（目标2）如何对互利共生崩溃的模拟做出反应。接下来，我们将通过追踪互惠基因工具包在新产生的基因组规模的同源性（Aim 3）中的进化来破译互惠崩溃的进化后果，并测试互惠崩溃的全基因组后果的竞争假设（Aim 4）。通过整合方法和跨越尺度，BREAKDOWN将实现对为什么一些谱系放弃互惠的预测性理解，以及这将带来什么样的进化后果。理解互利主义的崩溃对于解释自然界中互利主义的普遍性和预测依赖于它们的许多系统的潜在崩溃的条件都至关重要。

Cooperation among species -or mutualism- has driven some of the most important innovations across the tree of life, and provide us with key ecosystem services. While a great deal of effort has been put into understanding how mutualisms arise, we know surprisingly little of what leads to their breakdown. Why and when do mutualism break down? What are the direct evolutionary consequences for species that lose mutualism? My past research revealed that the level of partner dependence is a key predictor of mutualism breakdown at the macroevolutionary scale, with facultative lineages being more vulnerable to abandonment. Yet, the underlying mechanisms explaining this macroevolutionary pattern are unknown. The goal of my project, therefore, is to test the ecological processes and reveal the evolutionary consequences of mutualism breakdown. To achieve this, I will capitalize on the mutualistic system between epiphytic Rubiaceae plants (Hydnophytinae) and ants, which involves an exceptional number of independent mutualism breakdown events in a sizeable clade. My team will first experimentally test how physiology and traits (Aim 1) and gene expression (Aim 2) in facultative vs. obligate species respond to simulations of mutualism breakdown. Next, we will decipher the evolutionary consequences of mutualism breakdown, by tracing the evolution of the mutualistic gene toolkit across a newly generated genome-scale phylogeny (Aim 3), and test competing hypotheses underlying the genome-wide consequences of mutualism breakdown (Aim 4). By integrating approaches and crossing scales, BREAKDOWN will achieve a predictive understanding of why some lineages abandon mutualisms, and what evolutionary consequences this bears. Understanding mutualism breakdown is critical to both explaining the prevalence of mutualisms in the natural world and predicting the conditions for potential collapse of the many systems that rely upon them.