Entomology

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    GENETIC DIVERSIFICATION, SAPROPHYTIC COMPETENCE AND GENETIC ENHANCEMENT OF THE ENTOMOPATHOGENIC FUNGUS METARHIZIUM
    (2009) Pava-Ripoll, Monica Patricia; St. Leger, Raymond J; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Entomopathogenic fungi are being investigated as alternatives to chemical insecticides. This study explored the versatility of the entomopathogenic fungus Metarhizium anisopliae by examining its diversification, saprophytic competence and potential for genetic enhancement. M. anisopliae is a radiating species containing both generalist and specialized lineages with broad and narrow host ranges and as such provides an excellent model system to study the evolution of pathogenesis. Using 18S RNA and protease sequences, I demonstrated that strains can be selected representing evolutionary distances ranging from <1 to 8 MY and their natural molecular variation allows analysis of processes of adaptive change. M. anisopliae is particularly abundant in the rhizosphere. Germination of M. anisopliae strain 2575 was >96% in 1 mg/ml root exudate (RE) and growth in RE resulted in 29 (58%) genes being up-regulated and 21 (42%) down-regulated. The identity of these genes is helping to define the physiological requirements for rhizosphere competence. Hypothetical and orphans proteins (41.4%) were also actively expressed indicating that many previously uncharacterized genes may have functions related to survival at the soil-root interphase. Using the fungus as a delivery vehicle for foreign toxins presents a powerful approach for increasing virulence. M. anisopliae was modified to express a scorpion toxin (AaIT) in insect haemolymph and bioassayed against the coffee berry borer Hypothenemus hampei. AaIT increased mortality up to 56.6%, and reduced the medial lethal concentration (LC 50 ) by 15.7-fold and the average survival time (AST) by 20.1%. The AaIT gene and the M. anisopliae esterase gene (Mest1) were inserted into three strains of Beauveria bassiana (ARSEF 252, 8998 and 9184) with high, medium and low mortality, respectively, against the Colorado potato beetle (CPB) Leptinotarsa decemlineata. Mortality rates were strain- and dose- dependant and increased from 16.1 to 36.7% in single transformants (AaIT or Mest1) and from 7.1 to 33.5% in double transformants (AaIT-Mest1). The AST was reduced up to 33% and the LC50 up to 5.9-fold. Although singly both AaIT and Mest1 increased the killing power of B. bassiana against second instar CPB, combining AaIT and Mest1 together did not produce synergistic effects.
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    Systematics of Diparinae (Hymenoptera: Pteromalidae), and their position within the broader context of pteromalid phylogeny
    (2004-11-23) Desjardins, Christopher A; Mitter, Charles; Grissell, E. Eric; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Chalcidoidea, one of the largest superfamilies of parasitic Hymenoptera, has major importance in the biological control of insect pests. However, phylogenetic relationships both within and between chalcidoid families have been poorly understood, particularly within Pteromalidae, one of largest families. This study approaches the problem of pteromalid phylogeny from two directions, coupling a detailed morphological revision of one of the most divergent and poorly-known subfamilies of pteromalids (Diparinae) with a broad, exemplar-based molecular study that seeks to place this subfamily in the broader context of pteromalid and chalcidoid phylogeny. First, a morphological phylogenetic analysis of the world genera of Diparinae is provided based on 76 characters. Diparinae is supported as monophyletic based on the presence of a cercal brush in all analyses. The cercal brush, in combination with the absence of a smooth, convex dorsellum, is diagnostic for Diparinae. Liepara Boucek (Pteromalidae) and Bohpa Darling (Pteromalidae: Ceinae) both appear as sister-groups to Diparinae in different analyses. The phylogenetic analysis is used to develop a new classification scheme, under which Diparinae consists of 116 species in 14 genera. Three genera and 14 species are described as new, and a key to all genera is provided. Second, forty-two taxa broadly representing Chalcidoidea and more specifically Pteromalidae were sequenced for 4620 bp of four nuclear protein-coding genes, including 1719bp of CAD, 708bp of DDC, 1142bp of enolase, and 1044bp of PEPCK. The combined data set was analyzed using maximum likelihood methods, and the AU test was used to test support for non-monophyly of taxonomic groups which appeared para- or poly-phyletic in the tree. Phylogenetic relationships that have been supported by previous morphological and molecular evidence were recovered (e.g., monophyly of Chalcidoidea), as was the monophyly of groups well supported by morphology but resolved as polyphyletic in previous molecular analyses (e.g., Chalcididae). The monophyly of Pteromalidae and the pteromalid subfamily Colotrechninae are both strongly rejected (p<0.001). New hypotheses are proposed for relationships within Chalcidoidea, including Eutrichosomatinae (Pteromalidae) as the basal lineage of the perilampid/eucharitid clade. This study demostrates that molecular and morphological data can provide reciprocal illumination for understanding relationships within Chalcidoidea.
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    Revision of the Genera of the Rhagionidae of the World (Diptera: Brachycera)
    (2004-06-08) Kerr, Peter H.; Mitter, Charles; Woodley, Norman E.; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    As a group, flies represent one of the most prolific and important elements of our natural world. The order Diptera comprises approximately 150,000 species in approximately 142 families. My research focuses on the Rhagionidae (formerly known as the Leptidae), a family of flies considered to contain some of the most primitive living members of the dipteran suborder Brachycera and believed to have diversified as early as 170 million years ago. The taxonomic classification of the Rhagionidae has been unstable for decades because there are few morphological characters that can be used to support hypotheses of relationship among its members. Much of the morphology in this group, however, has not been examined systematically. An independent estimate of phylogeny for the group is carried out and presented here, based on 208 morphological characters for 43 ingroup species and molecular characters consisting of 3200+ bp sequences of 28S rDNA of 34 ingroup species. The goal of this work is to better understand how the genera of the Rhagionidae relate to one another and to their kin within the infraorder Tabanomorpha. Ultimately, this knowledge is fundamental for developing a stable classification system for the group. The Rhagionidae are recognized as a monophyletic group containing four subfamilies containing a total of 17 extant genera. The subfamily Spaniinae is defined by a special modification of tergite 9 of the female genitalia, which is shared by members of Omphalophora, Ptiolina, Spania, Spaniopsis, and Symphoromyia. Omphalophora Becker is resurrected from synonymy with Ptiolina. Spaniinae is defined by having scale-like thoracic hairs, as in Chrysopilus, Schizella and Stylospania. Arthroceratinae contains a single enigmatic genus, Arthroceras. Most females belonging to these three subfamilies have spermathecal duct accessory glands. These structures are reported here for the first time and are unique in Tabanomorpha. The Rhagioninae is the most primitive subfamily of the Rhagionidae. The saw sclerite in the larval mandible may be synapomorphic for this subfamily. Members of Rhagioninae include Atherimorpha, Desmomyia, Rhagio, and Sierramyia gen nov. Rhagina Malloch is recognized as a junior synonym of Rhagio. The Bolbomyiidae are recognized at the family level for the first time. Alloleptis tersus is incertae sedis within Tabanomorpha. Two new species are described: Schizella woodleyi (from Luzón, Philippines) and Sierramyia chiapasensis (from Chiapas, Mexico). A key is given to the genera of the Rhagionidae with dichotomies leading to all families of Tabanomorpha. Genera of Austroleptidae, Bolbomyiidae, and Rhagionidae are diagnosed and described, with a list of included species for each genus.