Collaborative Research: Higher order interactions, functional trait changes, and species coexistence in an annual plant community

自然群落通常由几十个或几百个相互作用的物种组成。然而，为了简单起见，生态学中物种相互作用的研究通常集中在物种对之间的相互作用上。生态学家通常认为，我们对物种之间相互作用的理解可以用来理解整个群落的动态。这一核心假设受到高阶相互作用（HOI）的挑战，高阶相互作用发生在一对物种之间的相互作用因第三物种的存在而改变时。HOI可以使物种更容易或更难在多样化的社区中共存，这取决于影响的强度和性质。因此，这些相互作用的可能存在从根本上挑战了我们对自然群落如何维持生物多样性的理解。然而，我们对自然界中HOI的强度或分布范围知之甚少。 该研究将量化草地群落中植物物种之间HOI的强度和流行程度，并测试植物物种的某些物理或生理特征是否更容易发生HOI。该项目将解决社区生态学中的一个基本挑战，培训一名研究生和博士后研究员，并用于改进高中、本科和研究生课程。 该研究将结合联合收割机大规模田间实验、植物功能性状的详细测量以及数学理论的应用，提出三个问题：（1）自然界竞争者之间的高阶相互作用（HOI）有多强？(2)HOI如何影响物种共存的机会？(3)生态学家能用植物功能特性的知识来预测自然界中这些相互作用的大小吗？该项目将通过在加州一年生植物群落中进行的大型实地实验，对近150种三向HOI的大小进行量化，使焦点物种同时受到两种不同竞争物种的不同密度的影响。然后将具有HOI的模型拟合到收集的人口统计数据。为了解决拟合HOI的共存后果，将在包括或排除这些HOI项的参数化模型中评估共存和物种持续时间的入侵条件。为了评估HOI的可预测性，该研究将测量植物功能性状如何对其他竞争者的密度做出可塑性反应，这些信息将用于预测拟合HOI的值。总之，这项研究将使生态学家既量化HOI物种共存的重要性，并确定其功能基础，奠定了这些相互作用的进一步机制研究的基础。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Natural communities are often composed of dozens or hundreds of interacting species. However, for simplicity, the study of species interactions in ecology most often focuses on interactions between pairs of species. Ecologists often then assume that our understanding of interactions between species pairs can be used to make sense of the dynamics of entire communities. This core assumption is challenged by the potential for Higher Order Interactions (HOIs), which occur when the interaction between a pair of species is changed by the presence of a third species. HOIs can either make it easier or more difficult for species to coexist in a diverse community, depending on the strength and the nature of the effects. The possible existence of these interactions therefore fundamentally challenges our understanding of how biodiversity is maintained in natural communities. However, we know very little about how strong or widespread HOIs might be in nature. The research will quantify the strength and prevalence of HOIs among plant species in a grassland community and test if certain physical or physiological characteristics of plant species make HOIs more likely to occur. The project will address a fundamental challenge in community ecology, train a graduate student and postdoctoral researcher, and be used to improve courses offered at the high school, undergraduate and graduate level. The research will combine large-scale field experiments, detailed measurements of plant functional traits, and the application of mathematical theory to ask three questions: (1) How strong are Higher Order Interactions (HOIs) among competitors in nature? (2) How do HOIs affect opportunities for species coexistence? (3) Can ecologists predict the magnitude of these interactions in nature with knowledge of plant functional traits? The project will quantify the magnitude of nearly 150 three-way HOIs through a large field experiment in a California annual plant community subjecting focal species to simultaneously varying densities of two different competitor species. Models with HOIs will then be fit to the demographic data collected. To address the coexistence consequences of the fitted HOIs, the invasion condition for coexistence and species persistence times will be evaluated in parameterized models that either include or exclude these HOI terms. To assess the predictability of HOIs, the research will measure how plant functional traits plastically respond to the densities of other competitors, and this information will be used to predict the value of the fitted HOIs. Taken together, the research will allow ecologists to both quantify the importance of HOIs for species coexistence and identify their functional basis, laying the groundwork for further mechanistic studies of these interactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.