Morphometry, molecular markers, and phylogeography of the rice weevil, Sitophilus oryzae (Linnaeus) and the maize weevil, S. zeamais Motschulsky (Coleoptera: Curculionidae)

This thesis examines the taxonomic and geographical relationships between grain pest weevils in the genus Sitophilus. Literature relating to the taxonomy and biological species concept of Sitophilus weevils is reviewed. Using a combination of morphological characters and molecular markers support the hypothesis that S. oryzae and S. zeamais are valid species that do not appear to interbreed in field populations. Genitalic characters are the only reliable morphological characters. Morphometric studies using PCA show that S. oryzae and S. zeamais formed two separate clusters, but this analysis is probably not useful for practical identification. Within species, there was substantial ITS-1 rDNA variation among geographical populations, but no strong geographical pattern. This is probably due to the extensive global grain traffic obscuring any divergence in grain pest populations.