A Phylogenetic Analysis of Armored Scale Insects (Hemiptera: Diaspididae), Based Upon Nuclear, Mitochondrial, and Endosymbiont Gene Sequences
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Molecular Phylogenetics and Evolution xxx (2010) xxx–xxx Contents lists available at ScienceDirect Molecular Phylogenetics and Evolution journal homepage: www.elsevier.com/locate/ympev A phylogenetic analysis of armored scale insects (Hemiptera: Diaspididae), based upon nuclear, mitochondrial, and endosymbiont gene sequences Jeremy C. Andersen a,*, Jin Wu a,b, Matthew E. Gruwell a,b,1, Rodger Gwiazdowski a,b, Sharlene E. Santana a, Natalie M. Feliciano c, Geoffrey E. Morse a,2, Benjamin B. Normark a,b a Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA b Department of Plant, Soil, and Insect Sciences, University of Massachusetts Amherst, Amherst, MA 01003, USA c Graduate Program in Plant Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA article info abstract Article history: Armored scale insects (Hemiptera: Diaspididae) are among the most invasive insects in the world. They Received 26 August 2009 have unusual genetic systems, including diverse types of paternal genome elimination (PGE) and parthe- Revised 12 April 2010 nogenesis. Intimate relationships with their host plants and bacterial endosymbionts make them poten- Accepted 2 May 2010 tially important subjects for the study of co-evolution. Here, we expand upon recent phylogenetic work Available online xxxx (Morse and Normark, 2006) by analyzing armored scale and endosymbiont DNA sequences from 125 spe- cies of armored scale insect, represented by 253 samples and eight outgroup species. We used fragments Keywords: of four different gene regions: the nuclear protein-coding gene Elongation Factor 1a (EF1a), the large Armored scale ribosomal subunit (28S) rDNA, a mitochondrial region spanning parts of cytochrome oxidase I (COI) Coccoidea Evolution and cytochrome oxidase II (COII), and the small ribosomal subunit (16S) rDNA from the primary bacterial Haplodiploidy endosymbiont Uzinura diaspidicola. Maximum likelihood, and Bayesian analyses were performed produc- Invasive species ing highly congruent topological results. A comparison of two datasets, one with and one without missing Parahaplodiploidy data, found that missing data had little effect on topology. Our results broadly corroborate several major Paternal genome elimination (PGE) features of the existing classification, although we do not find any of the subfamilies, tribes or subtribes Pseudoarrhenotoky to be monophyletic as currently constituted. Using ancestral state reconstruction we estimate that the Phylogeny ancestral armored scale had the late PGE sex system, and it may as well have been pupillarial, though Pupillarial results differed between reconstruction methods. These results highlight the need for a complete revision Sternorrhyncha of this family, and provide the groundwork for future taxonomic work in armored scale insects. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction netic system in which the paternal chromosomes in males are het- erochromatic and unexpressed throughout postembryonic Scale insects (superfamily Coccoidea) are a diverse group of development, and are eliminated during spermatogenesis (Brown, mostly sap-sucking insects, with at least 30 families and around 1965). 8000 species (Gullan and Cook, 2007). Female scale insects have The most species rich family of scale insects is Diaspididae, the a simplified morphology, with several fused segments, and none armored scales, with over 2400 described species (Miller and have any trace of wings. Like their sister group the aphids (super- Davidson, 2005; Miller and Gimpel, 2008). Traditionally, the ar- family Aphidoidea) and other members of the hemipteran subor- mored scales have been distinguished by their extreme modifica- der Sternorrhyncha, scale insects harbor vertically transmitted tion of adult female morphology, with the complete loss of legs endosymbionts that are believed to help synthesize amino acids and the reduction of eyes and antennae (Balachowsky, 1948). In missing from their diet (Buchner, 1965; Gruwell et al., 2005, some species, the adult female never sheds the second instar’s 2007). Most of these insects also have an unusual haplodiploid ge- derm and spends her entire life within its confines, a developmen- tal mode known as the pupillarial habit (Howell and Tippins, 1990). Many armored scales have a derived system of paternal * Corresponding author. Present address: Department of Environmental Science genome elimination (PGE) in which the paternal chromosomes in Policy and Management, University of California Berkeley, Berkeley, CA 94720, USA. males are completely eliminated during embryogenesis (Brown, E-mail addresses: [email protected], [email protected] (J.C. 1965). Andersen). 1 Armored scales have colonized every continent except Antarc- Present address: School of Science, Penn State Erie, Erie, PA 16563, USA. 2 Present address: Department of Biology, University of San Diego, San Diego, CA tica, and are among the most invasive insects in the world. Fully 92110, USA. 40% of the species found in the United States were introduced 1055-7903/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.ympev.2010.05.002 Please cite this article in press as: Andersen, J.C., et al. A phylogenetic analysis of armored scale insects (Hemiptera: Diaspididae), based upon nuclear, mitochondrial, and endosymbiont gene sequences. Mol. Phylogenet. Evol. (2010), doi:10.1016/j.ympev.2010.05.002 2 J.C. Andersen et al. / Molecular Phylogenetics and Evolution xxx (2010) xxx–xxx (Miller et al., 2005). In addition, the armored scales are among the olecaniidae, Bambusaspis miliaris; and two pseudococcids Fagisuga most polyphagous insects known, with some species feeding on triloba and Planococcus citri. For classification of armored scales we over 100 families of plants (McClure, 1990; Ben-Dov, 2008; Miller have followed Borchsenius’ classification (Borchsenius, 1966) as and Gimpel, 2008), even though a single individual will only ever modified by Takagi (Takagi, 1969, 1970, 1981, 1985, 1987, 1989, feed on a single host during its lifespan. Local adaptation to geno- 1992, 1993, 1995, 1998, 1999, 2000, 2002, 2003; Takagi et al., types of individual hosts has been inferred for some armored scale 1990, 1997). Specimens are stored at the University of Massachu- insects, even within polyphagous species (Hanks and Denno, 1994; setts, and are either frozen at 80 °C, or are preserved in 100% eth- À Glynn and Herms, 2004). Their invasive potential, small size, and anol and stored at 20 °C. À difficulty of identification make armored scales a major problem for plant quarantine workers around the world (Burger and Ulen- 2.2. DNA sequences berg, 1990). Recently, results of molecular phylogenetic studies have been applied successfully to the problem of molecular identi- Nucleic acids were isolated from specimens using the Qiagen fication of invasive armored scales (Edwards et al., 2008; Morse DNeasy Blood & Tissue Kit (Qiagen, Valencia, California), with the et al., 2009). following modifications. For fresh specimens, the insect was placed The study of these important and bizarre insects suffers from a in the cap of a 1.5 ml Eppendorf tube with 2 ll of Buffer ATL. lack of information about their phylogeny. Though many classifica- Microscope cover glass was broken into small fragments that were tions of armored scale insects have been proposed (Miller, 1990; slightly larger than the insect. Using sterilized forceps, the cover Takagi, 2002; Ben-Dov and German, 2003), there have been few glass was placed on top of the insect, and downward pressure quantitative studies of their relationships. The first was a phenetic was applied to force the body contents out. The cover glass was analysis of male morphological characters for 26 species by Ghauri rinsed with 20 ll of Buffer ATL, and then disposed of. Samples were (1962). Ghauri’s data were later subject to extensive reanalysis sometimes stored frozen for several days before 160 ll Buffer ATL using principal component and principal coordinate methods (Bor- was added to bring the volume to 180 ll as per Qiagen’s protocol. atyn´ ski and Davies, 1971; Davies and Boratyn´ ski, 1979; Davies, For insects preserved in 100% ethanol, the insect was punctured 1981). Miller (1990) reported preliminary results of a cladistic using a 000 entomology pin, and air dried before being placed in analysis of 70 morphological characters for 33 taxa, and a portion 180 ll of Buffer ATL. The Qiagen protocol was followed in both of Miller’s character matrix was later analyzed in conjunction with methods until the first elution, at which point only 40 ll of Buffer molecular data by Morse et al. (2005) for 28 species. To date, the AE was used. For all specimens, the cuticle was saved for mounting most thorough phylogenetic analysis of armored scale insects has on a microscope slide, and vouchers are maintained in the Univer- been that of Morse and Normark (2006), who examined two nucle- sity of Massachusetts Insect Collection. ar DNA regions (28S ribosomal DNA and Elongation Factor 1 alpha) Four gene regions were used: part of the nuclear protein-coding of 112 specimens in 89 species. gene Elongation Factor 1a (EF1a); the D2 and D3 expansion seg- Here, we expand upon the molecular dataset from Morse and ments of the large subunit ribosomal RNA gene (28S); a region of Normark (2006) and incorporate two additional gene regions, both mitochondrial DNA (mtDNA) encompassing the 30 portion of cyto- of which are maternally transmitted: