Biogéographie des mollusques marins de Polynésie française

Abstract

Biogeography of French Polynesia marine molluscs. The distribution of marine molluscs in each of the five archipelagos composing French Polynesia is presented with reference to 2053 species perfectly identified to the specific rank. The progress of knowledge on the distribution of molluscs and the limits of the inventory presented are discussed in relation to the reality of biodiversity. The species richness by archipelago is established and shows a degree of impoverishment along a longitudinal axis, from the Society to the Tuamotu and the Gambier, and along a latitudinal axis from north to south, from the Marquesas to the Society and the Austral. The distribution of species of marine molluscs allows to establish the species specific to each archipelago and those that are common to two or more archipelagos, which together determine the affinities between the archipelagos. The Marquesas and the Austral are very original in comparison with the Society, while the Tuamotu and even the Gambier are only impoverished faunas of the Society. The endemism in French Polynesia is 11.8 % (243 endemics out of 2053 species identified). Beyond this regional rate we can precise by archipelago two levels of endemism : that which is strict for the species whose distribution is limited to this archipelago and that which includes all the endemics, the strict ones and those present in at least one other archipelago : Marquesas (9.3 and 13.6 %) - Austral (6.8 and 12 %) - Society (2 and 6.5 %) - Tuamotu (2.3 and 7.9 %) - Gambier , 7 and 4.8 %). The richness of the marine mollusc fauna of French Polynesia is compared with that of Hawaii and the islands and archipelagos of the Eastern Pacific (Clipperton, Galapagos, Easter Island) and their high levels of endemism ; respectively : 11, 8 -20 -4 -17 and 42 %. The origin of the Polynesian marine mollusc fauna is evoked in relation to the Indonesian-Australian zone of maximum species richness with the confirmation that it operates since the Miocene as a center of dispersion creating at the margin of the Indo-Pacific province high places of speciation and endemism.