PHYLOGENY OF SYMBIOTIC BACTERIA OF 4 WEEVIL SPECIES (COLEOPTERA, CURCULIONIDAE) BASED ON ANALYSIS OF 16S RIBOSOMAL DNA

Weevils possess procaryotic symbiotes harbored in specialized organ-like structures, mycetomes. Inability to culture these bacterial symbiotes outside of the insect-host has hindered efforts to determine their taxonomic affiliation with respect to other eubacteria. In this report, molecular phylogenetic analysis of 16S ribosomal RNAs indicates that symbiotes from taxonomically divergent weevils are descendents of distinctly separate bacterial lineages. The intracellular symbiotes of two rhyncophorine weevils, Sitophilus oryzae L. and Sitophilus zeamais Mots., descended from the same hypothetical ancestor and share a common lineage with the secondary symbiote of the pea aphid, Acyrthosiphon pisum (Harris). These symbiotes are members of the Enterobacteriaceae in the gamma-3 subgroup of the Proteobacteria. The symbiotes of two cleonine weevils, Bangasternus orientalis (Capiomont) and Rhinocyllus conicus (Froelich), are phylogenetically distinct from the symbiotes found in the rhyncophorines and are members of a branch of the alpha-subdivision which include the cytoplasmic incompatibility microorganisms of insects (CIMS), Ehrlichia and Anaplasma. The implication of genetic divergence of bacterial symbiotes to weevil speciation is discussed.