Molecular systematics and evolution in an African cycad-weevil interaction: Amorphocerini (Coleoptera: Curculionidae: Molytinae) weevils on Encephalartos

Abstract

Weevils in the tribe Amorphocerini have been implicated in pollination of Encephalartos species in southern Africa. The services they render these plants and the unique attributes of the cycad-weevil interaction make them important from both conservation and evolutionary standpoints. Oberprieler [Oberprieler, R.G., 1996. Systematics and evolution of the tribe Amorphocerini, with a review of the cycad weevils of the world. Ph.D. dissertation, University of the Free State, Bloemfontein, South Africa], using morphological characters, proposed a tentative hypothesis of relationships among the Amorphocerini which is tested here using DNA sequence data. Sequences from one mitochondrial and three nuclear genes were used to infer phylogenetic relationships, levels of sequence divergence, evolution of host associations, and patterns of speciation in this tribe. The results are reasonably consistent with the morphological hypothesis of relationships and species concepts, though important differences are observed, particularly in relationships among a Porthetes hispidus Boheman species group, which is indicated to have experienced recent divergences. In general, low levels of sequence divergence among species within two of the three genera indicate a recent radiation of this tribe onto African cycads, thus while cycad–insect interactions have often been considered ancient this may not be the case for some extant interactions. A complex pattern of host shifts onto both closely related and more distantly related hosts is suggested.