Evolutionary diversification of new Caledonian Araucaria

Mai Lan Kranitz; Edward Biffin; Alexandra Clark; Michelle L Hollingsworth; Markus Ruhsam; Martin F Gardner; Philip Thomas; Robert R Mill; Richard A Ennos; Myriam Gaudeul; Andrew J Lowe; Peter M Hollingsworth

doi:10.1371/journal.pone.0110308

Evolutionary diversification of new Caledonian Araucaria

PLoS One. 2014 Oct 23;9(10):e110308. doi: 10.1371/journal.pone.0110308. eCollection 2014.

Affiliations

¹ Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom.
² Australian Centre for Evolutionary Biology and Biodiversity, Environment Institute, School of Earth and Environmental Science, University of Adelaide, Adelaide, Australia.
³ University of Edinburgh, Institute of Evolutionary Biology, Edinburgh, United Kingdom.
⁴ UMR CNRS MNHN UPMC EPHE 7205 Institut de Systématique, Evolution, Biodiversité, Muséum National d'Histoire Naturelle, Paris, France.

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.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Bayes Theorem
Biodiversity*
Biological Evolution*
Calibration
Fossils
New Caledonia
Phylogeny
Sequence Analysis, DNA
Time Factors
Tracheophyta / physiology*

Grants and funding

This work was supported by funds from the Darwin Trust of Edinburgh and the ANR project BIONEOCAL, the PPF MNHN ‘Structure et évolution des écosystèmes’ led by P. Grandcolas. The work of AJL and EB was supported by the Australian Research Council through a Super Science Fellowship (FS1102 00051) and Discovery Grant (DP0665859) awarded to AJL. The Royal Botanic Garden Edinburgh is supported by the Scottish Government's Rural and Environment Science and Analytical Services Division. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.