Entomology and Plant Pathology

Dr. Kevin Moulton, Assistant Professor

Research

Insect Systematics

Molecular Studies
Our research efforts in molecular systematics include (1) inferring phylogenetic relationships from molecular sequences to obtain cladograms with which to test hypotheses about morphological and ecological diversification as well as biogeographical patterns and (2) developing molecular diagnostics to differentiate closely related structurally similar species. Current molecular phylogenetic research foci include reconstruction of relationships within black flies (Simuliidae), tachinid flies (Tachinidae), and most recently, the order Collembola (springtails). Black flies and tachinids, respectively, have considerable medical-veterinary and agronomic importance, while Collembola are important components of the terrestrial detritivore guild.

A major component of our molecular phylogenetic research involves implementation of "new" single copy nuclearly encoded genes for phylogeny reconstruction. We have identified and categorized (see below) several hundred candidates. Our approach involved perusing annotations of fly genome sequencing projects (Drosophila melanogaster & Anopheles gambiae) for large (>500 AA) protein coding genes and assessing copy number and divergence via results from protein BLAST searches (NCBI). Results from these BLAST searches often lead to the discovery of noninsect orthologs useful for development of oligonucleotide primers. Genes were categorized as either slowly, moderately, or rapidly evolving, with the moderately fast evolving genes, such as rudimentary or CAD, generally possessing both slowly and rapidly evolving domains. Because categorically similar taxa are not equivalent in age and often developmentally (i.e., generation-time effect) and evolutionary rates of genes can differ considerably among lineages, our categorization method is predominantly for convenience. Evaluation of a gene's true phylogenetic utility within a clade can only be gauged by reconstructing relationships among a "test set" of taxa. We strive to evaluate 3-5 genes for each molecular phylogenetic study before commencing with more rigorous taxon sampling. We gauge phylogenetic utility by ease of alignment (clarity of homology assessment), node support (bootstrap & Bremer support), branch lengths (overtly short branch lengths will invariably lead to loss of resolution with increased taxon sampling), and, to the extent possible, by tree topology if relationships are "known", inferred perhaps in a previous study.

We are currently developing a DNA fingerprinting diagnostic to separate closely related morphologically similar species of insects. Our approach involves the use of several restriction endonucleases to create a restriction fragment length polymorphism (RFLP) profile of a large portion (4-8 kilobases) of the mitochondrial genome. Our initial application of this technique will be to provide the means to identify several species within the Simulium jenningsi species group, including several so-called cytospecies, so named because currently they are separable only through analysis of banding patterns (rearrangements) within larval giant salivary gland polytene chromosomes.

Morphological/Biodiversity studies
Many of the molecular phylogenetic studies in which I am involved also include a morphological component. Phylogenies based upon morphological data can be used in conjunction with molecular-based inferences to assess topological concordance, which is the best measure of phylogenetic accuracy. In addition, morphological, ecological, biogeographical characters can be scored in a data matrix and traced onto a molecular based tree to infer their evolution without the problem of circularity (inferring the evolution of the same characters used to generate the tree). There is also ample opportunity for laboratory members to conduct graduate- and postgraduate-level projects involving traditional taxonomic revisionary and biodiversity (sampling) studies.

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