Global plant diversity patterns: case studies from early branching legume clades

最近的所有研究都表明，物种多样性在进化史上的时间、跨地理区域和谱系之间的分布非常均匀。尽管人们普遍认为，多样性的增加推动了物种的多样化，但梳理出物种多样化的原因仍然是一个挑战。我实验室的研究重点是经济上重要的豆科植物(豆科)的系统学、系统发育和进化。豆科植物有765个属和约19,500个物种，是第三大开花植物家族，代表着植物进化多样化的最壮观例子之一，几乎存在于全球每一个生物群中。我们研究了该科以热带为主的基本谱系。我研究的长期目标是使用全面采样、稳健和良好分辨的系统发育来建立稳定的分类，并更好地了解宏观进化的形态、生态和生物地理模式。未来五年将实现三个目标。1)我们将研究全球多样化模式，以测试五个豆科基础支系之间和内部的显著比率变化。为了实现这一点，我们将使用系统基因组学方法对核基因100‘S进行测序，以生成全面采样的系统发育图。速率变化将从地理、生物群、功能特征和花卉进化方面进行研究。2)将研究与植物相关的内在特性，以检验性状相关的多样性。花卉特征将在两个在花部形态上表现出显著多样性的谱系--龙舌兰亚科和龙舌兰亚科中进行研究，与栖息地适应相关的功能特征将在凯撒皮亚科中进行研究，那里已经发生了对所有主要生物群的辐射。3)将对红豆亚科和红豆亚科的生物地理和生物群演化进行研究，以确定这些主要是湿润的森林分支的分布是否可以追溯到始新世早期至中期，即大多数豆科植物所建议的干燥环境多样化。利用化石校准的系统发育，我们将调查当今的地理和生态分布，推断祖先的生物群，寻找生物群转移的证据，并批判性地评估生物群保守性与地质历史在解释这两个分支的分布方面的相对重要性。我们最近的工作取得了重大进展，朝着更加稳健和稳定的基于系统发育的豆科植物分类。这里提出的研究提供了巩固这些努力的机会，以清楚地了解全球豆类多样性的模式。这一合作和基础广泛的研究项目为学生提供了植物系统学和进化方面的培训机会，这对更好地了解世界各地现有的生物多样性至关重要。

All recent studies suggest that species diversity is distributed very evenly through time, across geographical regions and amongst lineages in phylogenetic history. Although it is widely believed that increased variability drives species diversification, teasing apart the causes of diversification remains a challenge. Research in my laboratory focuses on systematics, phylogenetics and evolution of the economically important plant family Leguminosae (Fabaceae). With 765 genera and c. 19,500 species, legumes are the third largest flowering plant family, represent one of the most spectacular examples of evolutionary diversification in plants, and occur in nearly every biome across the globe. We study the mostly tropical basal lineages of the family. The long term objective of my research is to use comprehensively sampled, robust and well-resolved phylogenies to establish stable classifications and to better understand macro-evolutionary morphological, ecological and biogeographical patterns. Three objectives will be addressed in the next five years. 1) We will examine global patterns of diversification to test for significant rate shifts across and within the five basal legume clades. To achieve this, we will generate comprehensively sampled phylogenies using a phylogenomics approach to sequence 100's of nuclear genes. Rate shifts will be studied in relation to geography, biomes, functional traits and floral evolution. 2) Intrinsic plant-related characteristics will be studied to test for trait-dependent diversification. Floral characters will be examined in Detarioideae and Dialioideae, two lineages that exhibit remarkable diversity in floral morphology, and functional traits related to habitat adaptations will be studied in Caesalpinioideae, where radiations into all major biomes have occurred. 3) Biogeography and biome evolution will be studied in Detarioideae and Dialioideae to determine whether the distribution of these primarily wet forest clades can be traced to an early to mid-Eocene, dry environment diversification, as suggested for most legumes. Using fossil calibrated phylogenies, we will investigate present-day geographic and ecological distributions, infer ancestral biomes, look for evidence of biome shifts and critically evaluate the relative importance of biome conservatism versus geological history in explaining the distribution of these two clades. Our recent work has made significant progress towards a more robust and stable phylogenetically-based classification of legumes. The research proposed here offers scope to consolidate these efforts to clearly understand patterns of legume diversity across the globe. This collaborative and broadly based research program provides opportunities for training of students in plant systematics and evolution, which are essential to a better understanding of existing biodiversity worldwide.