title: Phylogeography and niche modelling of the relict plant Amborella trichopoda (Amborellaceae) reveal multiple Pleistocene refugia in New Caledonia.
abstract: Amborella trichopoda Baill. (Amborellaceae, Amborellales), the sole living member of the sister group to all other extant angiosperms, is endemic to New Caledonia. We addressed the intraspecific phylogeography of Amborella by investigating whether its present population genetic structure could be related to its current and past habitats. We found moderate range-wide genetic diversity based on nuclear microsatellite data and detected four well-differentiated, geographically distinct genetic groups using Bayesian clustering analyses. We modelled the ecological niche of Amborella based on the current climatic and environmental conditions. The predictive ability of the model was very good throughout the Central East mainland zone, but Amborella was predicted in the northern part of the island where this plant has not been reported. Furthermore, no significant barrier was detected based on habitat suitability that could explain the genetic differentiation across the area. Conversely, we found that the main genetic clusters could be related to the distribution of the suitable habitat at the last glacial maximum (LGM, c. 21,000 years BP), when Amborella experienced a dramatic 96.5% reduction in suitable area. At least two lineages survived in distinct putative refugia located in the Massif des Lèvres and in the vicinity of Mount Aoupinié. Our findings finally confirmed the importance of LGM rainforest refugia in shaping the current intra- and interspecific diversity in New Caledonian plants and revealed the possibility of an as yet unreported refugium. The combination of niche modelling and population genetics thereby offered novel insight into the biogeographical history of an emblematic taxon.
authors.affiliation: IRD, UMR DIADE, BP 64501, 34394, Montpellier Cedex 5, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Poncet
authors.forename: François
authors.initials: F
authors.lastname: Munoz
authors.forename: Jérôme
authors.initials: J
authors.lastname: Munzinger
authors.forename: Yohan
authors.initials: Y
authors.lastname: Pillon
authors.forename: Céline
authors.initials: C
authors.lastname: Gomez
authors.forename: Marie
authors.initials: M
authors.lastname: Couderc
authors.forename: Christine
authors.initials: C
authors.lastname: Tranchant-Dubreuil
authors.forename: Serge
authors.initials: S
authors.lastname: Hamon
authors.forename: Alexandre
authors.initials: A
authors.lastname: de Kochko
mesh_terms: D001499:Bayes Theorem; D016000:Cluster Analysis; D004463:Ecology / Q000379:methods; D017753:Ecosystem; D051456:Gene Flow; D014644:Genetic Variation; D005828:Genetics, Population / Q000379:methods; D005838:Genotype; D019684:Magnoliopsida / Q000235:genetics*; D018895:Microsatellite Repeats; D008957:Models, Genetic; D009510:New Caledonia; D058974:Phylogeography; D017422:Sequence Analysis, DNA
keywords: Amborella trichopoda; genetic variation; habitat suitability; last glacial maximum; niche modelling; refugia