Les insectes actuels témoins des passés de l’Afrique : essai sur l’origine et la singularité de l’entomofaune de la region afrotropicale

Abstract

Abstract. The extant insects witnessing the pasts of Africa: essay on the origin and singularity of the Afrotropical entomofauna. This essay on the evolutionary history of the Afrotropical insects puts together the systematic and the evolution of many groups of insects with the large features of the geological, palaeobiogeographic and palaeoenvironmental history of the African continent. It is carried out starting from a synthetic approach, which endeavours to analyse some broad outlines of the origin of the diversity of entomological faunas of this area. The general history of the insects on a world scale is rather well-known thanks to the fossils and began around 400 Myr ago with the fi rst recognized insect fossils. On the African continent, fossil insects remain relatively rare, or little studied, outside several deposits in Southern Africa, which show a high entomological diversity. The fi rst known fossil traces in Africa go back to the Permian (250-290 Myr) from Madagascar (Orthoptera) and South Africa, with the Whitehill Formation (Coleoptera: Permocupedidae). The fi rst African record of a modern-like fauna is Triassic . Modern lineages truly diversifi ed during the Cretaceous (Orapa site: 89-93 Myr). Despite the importance of these sites they are not truly representatives of the evolution of African insect faunas, in particular during the Tertiary period, when the African fauna acquired its originality. The Coleoptera: Scarabaeoidea came from Jurassic lineages but they mainly evolved during the Cenozoic with a crucial phase during the lower Oligocene for the coprophagous species due to the rapid radiation of the herbivorous mammals. Infortunatly, very few fossil Scarabaeoidea have been described from Africa. Africa draws its specifi city, as a biogeographic area, from the breakup of the Gondwanaland at the Cretaceous times. Did the old geographical continuity between the continents of the southern hemisphere have an infl uence on the extant faunas of these areas and in particular of the Afrotropical region? The taxa that present disjunct distributions on several parts of the southern continents are generally qualifi ed Gondwanian. They have remarkable rates of endemicity and one does not know a current representative to them out of the southern areas of the Southern hemisphere continents. However, the fossils suggest that these disjunct distributions could have been the results of processes of post-gondwanian extinctions rather than of the maintenance of original endemisms. The Mantophasmatodea, which are today endemics to Southern Africa, are known from the Eocene Baltic amber and the Middle Jurassic of China. It would be thus more judicious to use for these organisms the epithet of Mesozoic instead of Gondwanian taxa. Trans-Thethys exchanges between Africa and the Laurasian continent are well documented for the Vertebrates and for some insect taxa. One of the key periods of the splitting of Gondwana is the fi nal separation of the African and South American continents at the beginning of the late Cre...

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