Structure and genetic diversity of Ixora margaretae an endangered species

The dry forests of New Caledonia are an exceptional ecosystem because of their numerous endemic botanical species and their highly diversified fauna of insects, mollusks, reptiles and birds. Unfortunately, the area of the dry forests has been significantly reduced, mainly by human activities. Ecological, phenological and genetic analysis of Ixora margaretae, a symbolic species of the sclerophyll forest, has revealed contrasting traits among natural stands. The division of the natural range and then the separation of forest islands has greatly reduced the existing genetic variability of this species. The genetic diversity is strongly structured in genetic clusters which correspond well to specific ecotypes according to the environmental conditions and the forest types. Furthermore, genetic analysis of the reproductive and non-reproductive trees as well the half-sib families obtained by complete protection of mother trees has revealed substantial genetic drift which has resulted in increased loss of allelic variability. The total consumption of seeds by mainly rats confirms the observed absence of natural regeneration. All these results show that measures taken to protect the stands of dry forests will not be enough to maintain sufficient genetic variability of I. margaretae populations in the long term. Assisted regeneration with control of the increase in variability will be necessary to maintain the biodiversity of the species. The results obtained for I. margaretae must be confirmed with other symbolic species in order to take the necessary measures for the effective preservation of the dry forests in New Caledonia.