Population Genetics & Genomics and Ecological Niche Modeling Reveal the Evolutionary History of the New Caledonian Relict Amborella trichopoda (Amborellaceae)

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 Amborellaby 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 modeled the ecological niche of Amborella based on current climatic and environmental conditions. The predictive ability of the model was very good throughout the Central East mainland zone and 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 suitable habitat at the last glacial maximum (LGM, ca. 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.

Resequencing of individual Amborellaplants across the species' range reveals similar geographic structure with conservation implications plus evidence of a recent, major genetic bottleneck.

The combination of niche modelling and population genetics & genomics thereby offered novel insight into the biogeographic history of an emblematic taxon.