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

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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.