Phylogenomics illuminates the phylogeny of flower weevils (Curculioninae) and reveals ten independent origins of brood-site pollination mutualism in true weevils.

Weevils are an unusually species-rich group of phytophagous insects for which there is increasing evidence of frequent involvement in brood-site pollination. This study examines phylogenetic patterns in the emergence of brood-site pollination mutualism among one of the most speciose beetle groups, the flower weevils (subfamily Curculioninae). We analysed a novel phylogenomic dataset consisting of 214 nuclear loci for 202 weevil species, with a sampling that mainly includes flower weevils as well as representatives of all major lineages of true weevils (Curculionidae). Our phylogenomic analyses establish a uniquely comprehensive phylogenetic framework for Curculioninae and provide new insights into the relationships among lineages of true weevils. Based on this phylogeny, statistical reconstruction of ancestral character states revealed at least 10 independent origins of brood-site pollination in higher weevils through transitions from ancestral associations with reproductive structures in the larval stage. Broadly, our results illuminate the unexpected frequency with which true weevils-typically specialized phytophages and hence antagonists of plants-have evolved mutualistic interactions of ecological significance that are key to both weevil and plant evolutionary fitness and thus a component of their deeply intertwined macroevolutionary success.

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

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.