Collaborative Research: Niche and Neutral Controls over the Coexistence of Serpentine Annual Plants

生态群落中物种的广泛多样性为人类提供了许多生态系统服务。然而，科学家们才刚刚开始了解是什么因素维持了植物群落的多样性。是什么让生长最快、最具竞争力的植物免于导致其他物种灭绝？一个世纪以来，生态学家用“生态位差异”来回答这个问题，即植物物种在关键方面的差异使它们能够最大限度地减少竞争。例如，不同的植物可能从不同的土壤深度吸收水分。然而，最近生态学家开始认识到物种不需要不同就能共存。事实上，在数学模型中，相同的物种在很长一段时间内共存，提出了共存的另一种假设。该提案的主要研究者已经开发了一个新的框架来确定物种差异是否构成植物群落生物多样性的基础。这一框架基于这样一个事实：当物种密度下降到低水平时，“生态位差异”会给物种带来优势，从而降低它们灭绝的可能性，增加多样性。研究人员将评估生活在蛇形土壤上的加州一年生植物物种在稀有情况下是否会有这样的优势。在这样做的过程中，他们评估了生态位差异在维持这个独特而多样的栖息地的多样性方面所起的作用。更广泛的影响包括在两所大学培训研究生、发展生态教学模式、向贫困学校的学生伸出援助之手，以及增进对保育生境的了解。这项研究将是解决物种差异在控制生物多样性方面所起作用的首批实验研究之一。

The wide diversity of species found in ecological communities provides numerous ecosystem services to humankind. Yet scientists are only beginning to understand what factors maintain the diversity seen in plant communities. What keeps the fastest growing, most competitive plant from driving other species extinct? For a century, ecologists answered this question with "niche differences", where plant species differ in key ways that allow them to minimize competition. For example, different plants may take up water from different soil depths. Recently however, ecologists have come to recognize that species need not differ to coexist. In fact, identical species co-occur for long periods of time in mathematical models, raising an alternative hypothesis for coexistence. The principle investigators of this proposal have developed a novel framework for determining whether species differences underlie the biodiversity seen in plant communities. This framework relies on the fact that 'niche differences' give species advantages when they drop to low density, decreasing their probability of extinction and increasing diversity. The investigators will assess whether California annual plant species living on serpentine soils experience such advantages when rare. In so doing, they assess the role that niche differences play in maintaining diversity in this unique and diverse habitat. The broader impacts include the training of graduate students at two universities, the development of ecological teaching modules, outreach to students from underprivileged schools, and increased understanding of a habitat of conservation concern. The research will be among the first experimental studies addressing the role that species differences play in controlling biodiversity.