Dissertation Research: Phylogeny, Biogeography, and Rates of Speciation in Valerianaceae (Dipsacales)

进化生物学家和生态学家长期以来一直对表现出巨大形态多样性和占据广泛栖息地的物种的爆炸性辐射着迷。开花植物谱系缬草科包含300-350种，已被列入14-17属，其中近200种是南美洲特有的。这些物种表现出惊人的花和营养形式。据推测，南美洲的物种代表了最近的辐射。化石的可用性将使我们能够明确地测试生物地理学假说，并调查这一群体的物种形成率。本研究的目的是：1)利用多个DNA序列数据推断缬草科植物的系统发育；2)研究形态特征的进化；3)阐明缬草科植物的生物地理历史；4)评估物种形成率，重点研究南美辐射。这将是第一次对缬草科植物进行系统发育分析，其中包括来自每个属的物种的广泛样本，并将为研究进化和物种形成的速度提供几种新方法的经验应用。具体来说，我们将验证一个假设，即自大约3-6百万年前巴拿马地峡形成以来，已有200多种缬草科植物起源。该项目将补充正在进行的Dipsacales其他谱系的研究，并将增强我们对北半球生物地理和南美植物群起源的理解。虽然我们的主要目的是解决具有广泛进化意义的问题，但从保护的角度来看，这项研究有一个紧迫的因素。具体来说，现在在南美洲安第斯山脉发现的巨大多样性正受到人类对高海拔“paramo”植被的影响的威胁。

Evolutionary biologists and ecologists have long been fascinated by explosive radiations of species that exhibit tremendous morphological diversity and occupy a wide range of habitats. The flowering plant lineage Valerianaceae contains 300-350 species that have been placed in 14-17 genera, with nearly 200 of the species being endemic to South America. These species exhibit a striking range of floral and vegetative forms. It has been hypothesized that the South American species represent a recent radiation. The availability of fossils will allow us to explicitly test biogeographic hypotheses and investigate rates of speciation within this group. The goals of this study are: 1) to infer the phylogeny of Valerianaceae using several DNA sequence data sets, 2) to examine morphological character evolution, 3) to elucidate the biogeographic history of Valerianaceae, and 4) to assess rates of speciation, with an emphasis on the South American radiation. This will be the first phylogentic analysis of Valerianaceae to include a broad sample of species from each of the genera and will also provide an empirical application of several new methods for the study of rates of evolution and speciation. Specifically we will test the hypothesis that over 200 species of Valerianaceae have originated since the formation of the Isthmus of Panama some 3-6 million years ago. This project will compliment ongoing studies of other lineages of the Dipsacales and will enhance our understanding of Northern Hemisphere biogeography and the origin of the South American flora. While our main aim is to address questions of broad evolutionary significance, there is an element of urgency to this research from the standpoint of conservation. Specifically, the enormous diversity now found in the Andes of South America is threatened by human impacts on the high elevation "paramo" vegetation.