Investigating the Cradle of the Angiosperms Based on State-of-the-Art Parametric Biogeographic Methods
The origin of flowering plants (angiosperms) and their extraordinary diversity (ca. 250,000 species) remain one of the most enduring mysteries in evolutionary biology, generations of scientists have devoted much attention to this question. For a long time, the oldest known fossils of angiosperms were from the Mid-Cretaceous and these are strikingly similar to current angiosperm taxa. How could such an extraordinary diversity of species could have arisen in such a short time span? Most scientists studying this question have focused on the temporal aspect of it, by investigating developmental, paleobotanical and molecular divergence time issues. However, since Darwin hypothesized the existence of a now vanished isolated southern continent as the birthplace of angiosperms, the spatial aspect of angiosperm origin has been mostly neglected in the paleobotanical and molecular phylogenetic literature. Although the bulk of the oldest angiosperm fossils are from the Mid to Late Cretaceous, some fossils have recently been described from the Early Cretaceous of the Liaoning province in northeast China such as Sinocarpus, probably related to some core eudicot families, and Archaefructus, which cannot be unequivocally assigned to any extant angiosperm family. An even older fossil from the same region has been assigned to the Middle Jurassic (Schmeissneria) and the interpretation of this find is debated. This new evidence is compatible with recent estimates of divergence times based on molecular dating techniques that indicate an origin of the angiosperms clade sometime between the Middle and Early Jurassic.
In this project, started in December 2010, researchers are trying to understand the spatial origin of the angiosperms using a genus-level phylogenetic tree of the early-diverging angiosperms (ANITA + Magnoliids) inferred from plastid DNA sequence regions. The phylogenetic reconstruction and divergence time estimation are inferred simultaneously using state-of-the-art techniques and new fossil evidence (see above) as calibration. The spatio-temporal history of early lineages of angiosperms will be inferred using parametric methods in biogeography. These new biogeographic methods have the advantage that they integrate information on lineage divergence times and can be constrained according to paleogeographic evidence. The recent worldwide paleogeographic model proposed by the researchers involved in this study will be used to constrain the biogeographic inference. In addition, the effect of phylogenetic and dating uncertainty on the biogeographic reconstruction will be addressed by performing the optimization on a set of randomly selected trees from the divergence time estimation analysis. Several other plant groups will also be examined as the project progresses, such as Pandanaceae, some Sapindaceae and Myrtaceae.
By integrating several disciplines in biology and geology together with new methods in biogeographic inference this project will shed new light on the cradle of the angiosperms. Such kind of contribution will be most welcome by researchers in evolutionary biology but can also have repercussions in conservation.
Project started : December 2010
Key publications (updated October 2011)
- Buerki, S., Forest, F., Alvarez, N., Nylander, J.A.A., Arrigo, N. & Sanmartín, I. (2011). An evaluation of new parsimony-based versus parametric inference methods in biogeography: a case study using the globally distributed plant family Sapindaceae. Journal of Biogeography 38: 531-550.
Project partners and collaborators
Real Jardin Botanico, Madrid (Prof. Isabel Sanmartin).
University of Lausanne (Dr Nadir Alvarez)
Marie Curie Actions