title: Evolutionary diversification of new Caledonian Araucaria.
abstract: New Caledonia is a global biodiversity hotspot. Hypotheses for its biotic richness suggest either that the island is a 'museum' for an old Gondwana biota or alternatively it has developed following relatively recent long distance dispersal and in situ radiation. The conifer genus Araucaria (Araucariaceae) comprises 19 species globally with 13 endemic to this island. With a typically Gondwanan distribution, Araucaria is particularly well suited to testing alternative biogeographic hypotheses concerning the origins of New Caledonian biota. We derived phylogenetic estimates using 11 plastid and rDNA ITS2 sequence data for a complete sampling of Araucaria (including multiple accessions of each of the 13 New Caledonian Araucaria species). In addition, we developed a dataset comprising 4 plastid regions for a wider taxon sample to facilitate fossil based molecular dating. Following statistical analyses to identify a credible and internally consistent set of fossil constraints, divergence times estimated using a Bayesian relaxed clock approach were contrasted with geological scenarios to explore the biogeographic history of Araucaria. The phylogenetic data resolve relationships within Araucariaceae and among the main lineages in Araucaria, but provide limited resolution within the monophyletic New Caledonian species group. Divergence time estimates suggest a Late Cretaceous-Cenozoic radiation of extant Araucaria and a Neogene radiation of the New Caledonian lineage. A molecular timescale for the evolution of Araucariaceae supports a relatively recent radiation, and suggests that earlier (pre-Cenozoic) fossil types assigned to Araucaria may have affinities elsewhere in Araucariaceae. While additional data will be required to adequately resolve relationships among the New Caledonian species, their recent origin is consistent with overwater dispersal following Eocene emersion of New Caledonia but is too old to support a single dispersal from Australia to Norfolk Island for the radiation of the Pacific Araucaria sect. Eutacta clade.
authors.affiliation: Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
authors.forename: Mai Lan
authors.initials: ML
authors.lastname: Kranitz
authors.affiliation: Australian Centre for Evolutionary Biology and Biodiversity, Environment Institute, School of Earth and Environmental Science, University of Adelaide, Adelaide, Australia.
authors.forename: Edward
authors.initials: E
authors.lastname: Biffin
authors.affiliation: Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Clark
authors.affiliation: Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Hollingsworth
authors.affiliation: Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
authors.forename: Markus
authors.initials: M
authors.lastname: Ruhsam
authors.affiliation: Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
authors.forename: Martin F
authors.initials: MF
authors.lastname: Gardner
authors.affiliation: Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
authors.forename: Philip
authors.initials: P
authors.lastname: Thomas
authors.affiliation: Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Mill
authors.affiliation: University of Edinburgh, Institute of Evolutionary Biology, Edinburgh, United Kingdom.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Ennos
authors.affiliation: UMR CNRS MNHN UPMC EPHE 7205 Institut de Systématique, Evolution, Biodiversité, Muséum National d'Histoire Naturelle, Paris, France.
authors.forename: Myriam
authors.initials: M
authors.lastname: Gaudeul
authors.affiliation: Australian Centre for Evolutionary Biology and Biodiversity, Environment Institute, School of Earth and Environmental Science, University of Adelaide, Adelaide, Australia.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lowe
authors.affiliation: Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Hollingsworth
mesh_terms: D001499:Bayes Theorem; D044822:Biodiversity; D005075:Biological Evolution; D002138:Calibration; D005580:Fossils; D009510:New Caledonia; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013997:Time Factors; D064028:Tracheophyta / Q000502:physiology*