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Towards a comprehensive understanding of Oxera's island life

Gâteblé G., Barrabé L., Birnbaum P., Drew B.T., Isagi Y., Izuno A., Karnadi-Abdelkader G., Kawai R., Lavergne S., Suyama Y.. 2019. In : Flores Olivier (ed.), Ah-Peng Claudine (ed.), Wilding Nicholas (ed.). Book of abstracts talks of of the third international conference on Island ecology, evolution and conservation. Saint-Denis : Université de la Réunion, p. 121-121. International conference on Island ecology, evolution and conservation. 3, 2019-07-08/2019-07-13, Saint-Denis (Réunion).

Since the introduction of the island life concept by Wallace, isolated oceanic and relatively young islands have been the place to be to study and unravel evolutionary patterns among original groups within the tree of life. In these regards, the quite old New Caledonian archipelago has been relatively neglected despite hosting a world-class biome, perhaps because no de¿nitive cases of adaptive radi-ation have been detected there thus far. Here we present a detailed analysis of the radiation of the genus Oxera (Lamiaceae) based on a multidisciplinary study including domestication, interspeci¿c hy-bridization, kariology, anatomy, systematics, phylogenetics, pollination biology, ecology, conservation and population genetics. New Caledonia is the main center of Oxera diversi¿cation with about 33 endemic species plus a few more taxa in Papua New Guinea, Australia and Paci¿c islands. We have shown that Oxera originated from a single and quite recent dispersal event in New Caledonia about 4.5 million years ago, and has successfully established and diversi¿ed at an outstanding net rate of up to one species per million years. Establishment and rapid initial diversi¿cation of Oxera in New Caledonia was probably facilitated by arid conditions that may have created new biota at the beginning of the Pliocene. Concurrently, Oxera also underwent major shifts in pollination syndromes, dispersal modes and life forms that are now exhibited by its extant major clades. More recently, the drivers of speciation within the main clades are most likely due to allopatry and habitat shifts in relation to climatic oscillations and soil morphogenesis. Ongoing population genetic studies on several species from di¿erent clades (e.g. within the monocaulous baladica clade and especially on the Oxera baladica species complex) are highlighting more recent stories, while the complete genome sequencing of a taxon (Oxera pulchella subsp. grandi¿ora) is likely to deepen our outstanding of the past demographic history of several species and/or clades. In ¿ne, we hope the results will be of interest for the conservation of the most critically endangered Oxera taxa.

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