Abstracts (first author)
Molecular data and ecological niche modeling reveal the evolutionary history of the New Caledonian relict Amborella trichopoda (Amborellaceae)
Amborella trichopoda Baill. is the sole living member of a lineage (Amborellaceae, Amborellales) that may be over 200 Million years old, long before the re-emergence of present New Caledonia. We investigated the biogeographic history of Amborella using a combined population genetics, species current distribution and palaeo distribution modelling approaches. We present here the first study carried out on Amborella trichopoda genetic and ecological variation in its natural distribution. We analyzed the pattern of genetic structure of 18 populations distributed throughout its geographical range. We found significant differentiation between any pair of locations, and four main well-differentiated, geographically distinct genetic groups were inferred using the Bayesian clustering algorithm in Structure software. To assess and understand the spatial distribution of genetic diversity in relation with habitat suitability, we modeled the ecological niche of Amborella trichopoda using Maxent both in the present-day and during the Last Glacial Maximum (LGM) climatic conditions. The model based on current climatic and environmental conditions (Topography, Rainfall, Temperature, Pedology) fitted well the actual distribution of the species. The southern genetic group appears partly separated from the rest of the populations by an ecological barrier of ultramafic land. For the other groups, we found the cumulated habitat distances to be correlated with geographic distances, so that there was no barrier in suitable habitat that could explain the genetic differentiation of the groups. This suggests other biogeographic constraints, while the genetic differentiation within each of the groups clearly follows the isolation by distance model. Indeed, the spatial delineation of the largest genetic groups is consistent with the forests having been isolated for multiple glacial-interglacial cycles, as predicted by the LGM modeling.