title: New Caledonian lineages of Psychotria (Rubiaceae) reveal different evolutionary histories and the largest documented plant radiation for the archipelago.
abstract: New Caledonia is a remote archipelago of the South-West Pacific, whose flora is rich, distinctive, and disharmonic. The interest of botanists has long been attracted by the spatio-temporal origin of this flora, but little attention has been paid to the modes of colonization and the diversification processes that have led to the archipelago's modern flora. To date, no explosive plant radiation has yet been highlighted for New Caledonia. A dated phylogenetic framework on the second richest New Caledonian genus--Psychotria s.l. and its allied genera (tribes Psychotrieae and Palicoureeae, Rubiaceae; ca. 85 species)--is provided in this study to explore its patterns of colonization and diversification in the archipelago. This study is based on a comprehensive species sampling, two nuclear and four plastid loci. Results show that New Caledonia was colonized four times by Psychotria and its allied genera during the Neogene long after its mid-Eocene re-emergence from the sea. The Pacific clade of Psychotrieae, one of the largest plant diversifications in the Pacific islands and the Indo-Pacific region, is absent from New Caledonia, possibly due to niche competition. Although the four lineages colonized New Caledonia relatively simultaneously during the Neogene, they express different evolutionary histories, as revealed by unevenness in species richness and net diversification rates. The genus Geophila has not diversified on New Caledonia, as a non-endemic single species has been documented in the archipelago. The genus Margaritopsis had a moderate level of diversification (four species) similar to that on other Pacific islands. The Psychotria clade NC1 appears to be a relictual lineage, which probably underwent a drastic extinction, with a narrow ecological habitat and dispersal limitations. The Psychotria clade NC2 is the largest and youngest New Caledonian plant radiation, and has undergone the fastest recorded diversification of any endemic lineage in the archipelago, and could be the result of a 'non-adaptive radiation', originating from Australian rainforests.
authors.affiliation: CIRAD, UMR AGAP, 98800 Nouméa, New Caledonia, France; IAC, BP 18239, 98857 Nouméa sud, New Caledonia, France. Electronic address: laure.barrabe@gmail.com.
authors.forename: Laure
authors.initials: L
authors.lastname: Barrabé
authors.affiliation: CIRAD, UMR AGAP, 98800 Nouméa, New Caledonia, France; IAC, BP 18239, 98857 Nouméa sud, New Caledonia, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Maggia
authors.affiliation: Tropical Conservation Biology and Environmental Science, University of Hawai'i at Hilo, 200 West Kawili Street, Hilo, HI 96720, USA.
authors.forename: Yohan
authors.initials: Y
authors.lastname: Pillon
authors.affiliation: IRD, Institut Méditerranéen de Biodiversité et d'Ecologie, UMR CNRS 7263/IRD 237, 98848 Noumea, New Caledonia, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Rigault
authors.affiliation: Université de Franche-Comté, UMR CNRS 6249 Chrono-Environnement, 16 route de Gray, 25030 Besançon cedex, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Mouly
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK.
authors.forename: Aaron P
authors.initials: AP
authors.lastname: Davis
authors.affiliation: Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK. Electronic address: s.buerki@kew.org.
authors.forename: Sven
authors.initials: S
authors.lastname: Buerki
mesh_terms: D001499:Bayes Theorem; D044822:Biodiversity; D010139:Pacific Islands; D010802:Phylogeny; D032069:Psychotria / Q000235:genetics*; D017422:Sequence Analysis, DNA
keywords: Dispersal mode; Diversification; Island colonization; New Caledonia; Phylogenetic dating; Psychotria s.l.