ONLINE IMAGE COLLECTION

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Flowered trunk of an old tree of the New Caledonian endemic Ixora cauliflora in a small population in a gallery forest of the Nétéa tribe valley in the center of “Grande Terre” in New Caledonia. Ixora cauliflora, with its spectacular flowerings along the trunk, has a high ornamental potential. The species is opportunist and grows in dry, mesic, or humid forests in sandy or humiferous soil. Cauliflorous species are very rare in Ixora and restricted to the Pacific Islands, with two endemics to New Guinea, one to the Solomon Islands, three to New Caledonia, and one to Raiatea Island in French Polynesia (seven of ca. 500 species in this pantropical genus). Cauliflory evolved several times in the Ixora according to phylogenetic data . Inflorescences consist of a cluster of solitary flowers borne on undifferentiated peduncles above leaf scars. This evolution is probably related to a pollination syndrome, as observed in several flowering plant groups in the Pacific. Ixora species are recognized for secondary pollen presentation; during the flower bud stage, a pollen mass is deposited on the stigmatic head, where the mass is presented to pollinators at anthesis. Flowers open at night when they are very odiferous and the corolla tubes are full of nectar to attract pollinators (mainly Sphingideae, a nocturnal insect group with rostra long enough to capture the nectar). In the case of I. cauliflora, the long corolla tube and the position of the inflorescences may be a specialization for large hawkmoths with long rostra.

For further detail, see: Mouly et al.— Phylogeny and classification of the giant pantropical showy genus Ixora (Rubiaceae-Ixoreae) with indications of geographical monophyletic units and hybrids, Volume 96, Issue 3, pages 686–706. Photo credit: A. Mouly.