A phylogenetic analysis of armored scale insects (Hemiptera: Diaspididae), based upon nuclear, mitochondrial, and endosymbiont gene sequences

Armored scale insects (Hemiptera: Diaspididae) are among the most invasive insects in the world. They have unusual genetic systems, including diverse types of paternal genome elimination (PGE) and parthenogenesis. Intimate relationships with their host plants and bacterial endosymbionts make them potentially important subjects for the study of co-evolution. Here, we expand upon recent phylogenetic work (Morse and Normark, 2006) by analyzing armored scale and endosymbiont DNA sequences from 125 species of armored scale insect, represented by 253 samples and eight outgroup species. We used fragments of four different gene regions: the nuclear protein-coding gene Elongation Factor 1α (EF1α), the large ribosomal subunit (28S) rDNA, a mitochondrial region spanning parts of cytochrome oxidase I (COI) and cytochrome oxidase II (COII), and the small ribosomal subunit (16S) rDNA from the primary bacterial endosymbiont Uzinura diaspidicola. Maximum likelihood, and Bayesian analyses were performed producing highly congruent topological results. A comparison of two datasets, one with and one without missing data, found that missing data had little effect on topology. Our results broadly corroborate several major features of the existing classification, although we do not find any of the subfamilies, tribes or subtribes to be monophyletic as currently constituted. Using ancestral state reconstruction we estimate that the ancestral armored scale had the late PGE sex system, and it may as well have been pupillarial, though results differed between reconstruction methods. These results highlight the need for a complete revision of this family, and provide the groundwork for future taxonomic work in armored scale insects.