Origin and Evolution of the New Caledonian Flora
The Kew team in collaboration with international researchers is investigating the origin and evolution of the New Caledonian flora.
New Caledonia, an archipelago located in the Southwest Pacific on the eastern margin of the Australian plate ca. 1200 km east of Queensland and ca. 1700 km north of New Zealand – is well known for its rich, endangered and highly endemic flora, hence its recognition as a biodiversity hotspot. The principal island, Grande Terre, in large part comprises a continental fragment that separated from Australia sometime during the Late Cretaceous (ca. 83 million years ago) but was subsequently submerged, especially during the Palaeocene, when the island’s characteristic ultramafic substrates were laid down deep under the ocean, emerging only during the Oligocene. The island’s flora, while entirely derived from elements that reached New Caledonia starting in the Oligocene, has diversified remarkably since then, resulting in a modern flora comprising 3,371 native vascular plant species, 74.4% of which are endemic. New Caledonia is home to many distinctive and evolutionary important groups, perhaps the most notable being the earliest-diverging lineage of angiosperms, represented by a single endemic species, Amborella trichopoda Baill., the sole representative of an order (Amborellales) whose origin is estimated to date to sometime between the Middle and Early Jurassic, long before the re-emergence of modern New Caledonia. This apparent contradiction between geological and biological data has triggered recent studies on the spatio-temporal evolution of the New Caledonian flora (e.g., Ebenaceae; Ericaceae, Sapotaceae).
A team from Kew team with international researchers is investigating the origin and evolution of the New Caledonian flora by focusing at the family level (using plastid and nuclear DNA sequencing), and the population level (using DNA fingerprinting methods). At the family level the research is mainly focused on Pandanaceae and Sapindaceae, however other families will eventually be scrutinized. In order to allow the comparison of the results across the angiosperms, a biogeographic framework was developed mainly based on paleogeography. At the population level, the team is focusing on species of the endemic genera of Sapindaceae (Podonephelium, Storthocalyx). This approach illustrate well the importance of the integration of large-scale (e.g. tempo and origin of dispersal events into New Caledonia) and fine scale (e.g. importance of abiotic and biotic in the diversification of New Caledonian lineages) evolutionary processes involved in shaping the current diversity. In addition, the phylogenetic frameworks will be used as guidelines to assess generic delimitations and eventually propose new classifications.
Sapindaceae (Sapindales) are a conspicuous and diversified element of the New Caledonian flora, with ca. 68 species (89.7% endemic) in 13 genera (four endemic: Gongrodiscus, Loxodiscus, Podonephelium and Storthocalyx). The phylogeny of New Caledonian Sapindaceae (included in a previous worldwide dataset) indicates that members of the family on the island belong to two major clades, the Dodonaea group (Dodonaeoideae) and the Cupania (Sapindoideae), which exhibit strikingly different species diversities (ca. 89% of the species on New Caledonia belong to the Cupania group). Results support the monophyly of all four endemic genera and most of those that also occur elsewhere, with the exception of the morphologically similar Austro-Pacific genera Arytera and Cupaniopsis, both of which have representatives in each of two well supported subclades within the Cupania group, suggesting at least two dispersals to New Caledonia (most likely from Australia). The results provide a robust phylogenetic framework for ongoing taxonomic revisions of Sapindaceae genera on New Caledonia and for investigating the spatio-temporal history of the family in this biogeographically intriguing archipelago.
Project duration: 2009-2014
Key publications 2009-2011
- Buerki, S., Forest, F., Callmander, M.W., Lowry II, P.P., Devey, D.S. & Munzinger, J. (----). Phylogenetic inference of New Caledonian lineages of Sapindaceae: molecular evidence requires a reassessment of generic circumscription. Taxon (in press in 2011).
- Duangjai, S, Samuel, R., Munzinger, J., Forest, F., Wallnöfer, B., Barfuss, M.H.J., Fischer, G. & Chase, M.W. (2009). A multi-locus plastid phylogenetic analysis of the pantropical genus Diospyros (Ebenaceae), with an emphasis on the radiation and biogeographic origins of the New Caledonian endemic species. Molecular Phylogenetics and Evolution 52: 602-620.
Project partners and collaborators
Institut de Recherche pour le Développement (IRD), UMR AMAP, Montpellier (Dr Jérôme Munzinger)
Institut de Recherche pour le Développement (IRD), UMR AMAP, Laboratoire de Botanique et d'Écologie Appliquées, Herbarium NOU (Dr Jérôme Munzinger)
Missouri Botanical Garden, Saint-Louis (Dr Porter P. Lowry II, Dr Martin W. Callmander)
Idaho Botanical Research Foundation