Spatio-temporal evolution of Cedreleae (Cedrela, Toona) from Paleocene to Pleistocene

雪松属(Meliaceae)是世界上最具经济价值和开发利用价值的木材属之一，但其分类地位并不令人满意。通过确定进化物种之间的边界，可以询问物种边界与什么特征相关，物种的各种方面是否倾向于一致进化，以及外部环境在产生遗传和表型集群方面发挥了什么作用。拟议项目的一个主要目的是根据全球气候变化和古新世至上新世的构造历史，调查单系部落雪松(新大陆雪松，东半球香椿)的时空演化。这一时期的气候变化被认为是形成梧桐科植物空间格局的驱动力。香椿的分布范围包括中南美洲(新大陆)，香椿分布于印度、印度支那-中国、马来西亚和澳大拉西亚(旧大陆)。从始新世到中新世，这两个属都是北半球热带植物区系的一部分，欧亚和北美以及以前连接大陆的地区(北大西洋大陆桥，贝林贾)的一些化石发现证实了这一点。对于塞德雷拉，多个化石发现表明，从中新世到上新世，从北美向南迁移到中美洲。我们将在特定和亚特定水平上对两个属采用多基因系统发育学，通过化石校准或限制在时间范围内设定。结合物种地理和生态属性的信息和分布区地质历史的知识，我们想要回答以下问题：(1)雪松在什么时候和在什么背景下分化为雪松和香椿？(2)雪松的多样性是否与栖息地生态位要求有关？(3)分布在雨林和干旱地区的广泛和可变的低地物种是由雪松的干燥森林物种与当地范围派生的吗？(4)生态/气候偏好的相似性与雪松物种的进化关系是否相关？结果将被纳入Cedrela的现代通用专著(Pennington和Muellner正在编写中)，并作为建立IUCN受威胁物种红色名单评估的信息来源。此外，Cedrela的DNA数据可以作为官方当局今后鉴定木材的条形码。

Although Cedrela (Meliaceae) is one of the world´s economically most important and exploited timber genera, its taxonomic status is by no means satisfactory. By identifying boundaries between evolutionary species, it is possible to ask what features are associated with species boundaries, whether the multifarious aspects of species tend to evolve in concert, and what role the external environment plays in producing genetic and phenotypic clusters. A major aim of the proposed project is the investigation of the spatio-temporal evolution of the monophyletic tribe Cedreleae (New World Cedrela, Old World Toona) in the light of global climate change and tectonic history from Paleocene to Pliocene. Climate change during this period of time is known to have been a driving force for shaping spatial patterns of Meliaceae. The distribution range of Cedrela comprises Central and South America (New World), whereas Toona is distributed throughout India, Indo-China, Malesia, and Australasia (Old World). From Eocene to Miocene the two genera were both part of the tropical flora of the Northern Hemisphere, which is corroborated by a number of fossil findings in Eurasia and North America and in areas formerly linking the continents (North Atlantic land bridge, Beringia). For Cedrela, multiple fossil findings indicate southward migration from North America to Central America from the Miocene to Pliocene. We will employ multi-gene phylogenies for both genera on specific and infra-specific level, set in a temporal context by fossil calibrations or constraints. Together with information on the geographical and ecological attributes of species and knowledge about the geological history of the distributional areas, we want to answer the following questions: (1) At what time and in which setting did Cedreleae diverge into Cedrela and Toona?;(2) Was diversification in Cedrela associated with habitat niche requirements?;(3) Were widespread and variable lowland species distributed in rain forest and in drier areas derived from dry forest species of Cedrela with local ranges?;(4) Is similarity of ecological/climate preferences correlated with evolutionary relatedness of species in Cedrela? Results will be incorporated in a modern generic monograph of Cedrela (Pennington and Muellner, in preparation) and serve as source of information for setting up IUCN Red List assessments for species under threat. In addition, DNA data of Cedrela might act as barcodes for future identification of timber by official authorities.