Using tribe cariceae (cyperaceae) as a model system to test ecological and evolutionary theory

生物多样性及其因人类活动造成的损失日益受到生物学家的关注，了解生物多样性的起源、维持和分布有助于在面对全球气候变化和人类活动水平的情况下进行保护规划。实现这种理解的一个困难是，自然规律、历史偶然性和偶然事件的相对作用很难分开。最近的研究在方法和范围上各不相同，从特定科和属的系统发育到种群的遗传结构，再到多样性热点的地理。我和我的学生在一个单一的大型植物谱系的背景下研究这些问题，Cariceae部落（苏柏科），通常被称为莎草。这一组包括广泛分布的Carex属，有近2000种（全球10大属之一）和4个较小的属，分布更有限，嵌套在其中。该类群具有世界性分布，大多数物种分布在温带、寒带、北极、高山和亚热带地区，它们的栖息地随日照、湿度、海拔和营养的梯度而变化。在一个单一的大型、多样化和广泛分布的进化分支中进行研究，为检验生态学和进化的几个领域的假设提供了一个无与伦比的系统：1)与栖息地和地理范围有关的多样化模式和特征进化；2)局地适应与散布等随机因子对植物群落聚集的相对重要性；3)不同环境条件下的适应性辐射和特征演化；4)物种丰富度和特有模式，以指导保护重点。我们将继续使用DNA序列来重建这一群体的进化历史（系统发育），并利用这一系统发育来研究植物群落组装的进化约束，特别是在极端环境下。我们还将比较在北美东部和东亚进化的平行毛苔系的功能特征的进化，以了解在过去1500万年的独立进化中，这些特征之间的相互关系和进化顺序的限制。

Biodiversity and its loss due to human activities is an increasing concern to biologists and understanding the origin, maintenance, and distribution of biodiversity can help conservation planning in the face of global changes in climate and levels of human activity. One difficulty in achieving this understanding is that the relative roles of natural laws, historical contingency, and chance events are hard to disentangle. Recent studies vary in approach and in scope from the phylogeny of particular families and genera, to the genetic structure of populations, to the geography of diversity hotspots. My students and I study these issues in the context of a single large lineage of plants, tribe Cariceae (Cyperaceae), commonly known as sedges. This group includes the broadly distributed genus Carex with nearly 2000 species (among 10 largest genera, globally) and four smaller genera with more restricted distributions that are nested within it. The group has a cosmopolitan distribution with most species found in temperate, boreal, arctic, alpine, and subtropical regions in a variety of habitats that vary along gradients of insolation, moisture, elevation, and nutrition. Working within a single large, diverse and widespread clade provides an unparalleled system for testing hypotheses in several fields of ecology and evolution: 1) patterns of diversification and trait evolution in relation to habitat and geographic range; 2) the relative importance of local adaptation and stochastic factors like dispersal to plant community assembly; 3) adaptive radiation and character evolution in response to different environmental conditions; and 4) patterns of species richness and endemism to guide conservation priorities. We will continue using DNA sequences to reconstruct the evolutionary history (phylogeny) of this group and use this phylogeny to study the evolutionary constraints on plant community assembly, especially in extreme environments. We will also compare the evolution of functional traits in parallel lineages of Carex that have evolved in Eastern N. America and Eastern Asia to understand constraints on the order of evolution and correlations among these traits during the past 15 million years of independent evolution.