|| 要旨トップ | 本企画の概要 |||日本生態学会第64回全国大会 (2017年3月、東京) 講演要旨
シンポジウム S10-2 （Lecture in Symposium）
Many clades have rapidly diversified on oceanic islands due to ecological opportunities that may have triggered adaptive radiations. Such radiations have not yet been demonstrated in the New Caledonian biodiversity hotspot. The sub-endemic, species rich genus Oxera (Lamiaceae) is suspected to have experienced an adaptive radiation, since it exhibits strongly divergent morphological and ecological attributes. Here, by integrating phylogenetics, fossil dating, and comparative analyses of niche evolution and species diversification rates, we investigate whether Oxera is a unique example of an adaptive radiation in New Caledonia. We show that Oxera is a Pliocene radiation, with an early diversification burst probably triggered by newly vacant niches opened by aridification around 5 Myr. Oxera seems to be the fastest New Caledonian plant radiation, without no diversification slowdown until present. Changing ecological opportunities have contributed to this radiation, with the diversification of biotic traits (life-form, pollination, dispersal) between 5-3 Myr, and more recent diversification in habitat preferences. Allopatric divergences have consistently occurred, leading to rare coexistence between closely related species, probably due to past climatic fluctuations, and complex microtopographies. Oxera can be regarded as a partial adaptive radiation, with joined action of geographic and ecological factors driving species diversification.